{"id":3162,"date":"2026-04-21T05:08:54","date_gmt":"2026-04-21T05:08:54","guid":{"rendered":"https:\/\/multahost.com\/blog\/?p=3162"},"modified":"2026-04-21T05:17:24","modified_gmt":"2026-04-21T05:17:24","slug":"vos3000-sip-routing-gateway-contact","status":"publish","type":"post","link":"https:\/\/multahost.com\/blog\/vos3000-sip-routing-gateway-contact\/","title":{"rendered":"VOS3000 SIP Routing Gateway Contact: Essential INVITE Header Guide"},"content":{"rendered":"\n<h1 class=\"wp-block-heading\" id=\"vos-3000-sip-routing-gateway-contact-essential-invite-header-guide\">VOS3000 SIP Routing Gateway Contact: Essential INVITE Header Guide<\/h1>\n\n\n\n<p>\ud83d\udcde When VOS3000 sends a SIP INVITE to a routing gateway, which header determines the callee number? Is it the <strong>To<\/strong> header, the <strong>Request-Line<\/strong>, or the <strong>Contact<\/strong> header? The answer depends on a critical \u2014 yet often overlooked \u2014 parameter: <strong>SS_SIP_ROUTING_GATEWAY_INVITE_USE_CONTACT<\/strong>, which governs the <strong>VOS3000 SIP routing gateway contact<\/strong> behavior for outbound INVITE messages. \ud83c\udfaf<\/p>\n\n\n\n<p>\ud83d\udd04 By default, this parameter is set to <strong>Off<\/strong>, meaning VOS3000 uses the standard SIP convention where the callee number is taken from the <strong>To<\/strong> header. But when enabled (<strong>On<\/strong>), VOS3000 extracts the callee number from the <strong>request-line<\/strong> of the INVITE and preserves the original number in the <strong>To<\/strong> field. This subtle change has a significant impact on how calls are routed through your VoIP softswitch \u2014 especially when interfacing with gateways that rely on the Contact header or request-line for number identification. \ud83d\udd27<\/p>\n\n\n\n<p>\ud83d\udce1 This guide covers everything you need to know about the VOS3000 SIP routing gateway contact setting \u2014 from the core parameter SS_SIP_ROUTING_GATEWAY_INVITE_USE_CONTACT to the related per-gateway SIP settings (Reply address, Request address, Peer number information) and Mapping Gateway callee\/caller field selection. All data is sourced exclusively from the official VOS3000 V2.1.9.07 Manual, Section 4.3.5.2 (Table 4-3). For expert assistance, contact us on WhatsApp at <strong>+8801911119966<\/strong>. \ud83d\udca1<\/p>\n\n\n\n<div class=\"wp-block-rank-math-toc-block\" id=\"rank-math-toc\"><h2>Table of Contents<\/h2><nav><ul><li><a href=\"#vos-3000-sip-routing-gateway-contact-essential-invite-header-guide\">VOS3000 SIP Routing Gateway Contact: Essential INVITE Header Guide<\/a><ul><li><a href=\"#\ud83d\udd10-what-is-vos-3000-sip-routing-gateway-contact\">\ud83d\udd10 What Is VOS3000 SIP Routing Gateway Contact?<\/a><ul><li><a href=\"#\ud83c\udfaf-why-vos-3000-sip-routing-gateway-contact-matters\">\ud83c\udfaf Why VOS3000 SIP Routing Gateway Contact Matters<\/a><\/li><\/ul><\/li><li><a href=\"#\u2699\ufe0f-how-ss-sip-routing-gateway-invite-use-contact-works\">\u2699\ufe0f How SS_SIP_ROUTING_GATEWAY_INVITE_USE_CONTACT Works<\/a><\/li><li><a href=\"#\ud83d\udccb-per-gateway-sip-settings-reply-address-and-request-address\">\ud83d\udccb Per-Gateway SIP Settings: Reply Address and Request Address<\/a><ul><li><a href=\"#\ud83d\udce8-reply-address-where-to-send-reply-signal\">\ud83d\udce8 Reply Address: Where to Send Reply Signal<\/a><\/li><li><a href=\"#\ud83d\udce4-request-address-where-to-send-request-signal\">\ud83d\udce4 Request Address: Where to Send Request Signal<\/a><\/li><li><a href=\"#\ud83d\udc64-peer-number-information-caller-selection-mode\">\ud83d\udc64 Peer Number Information: Caller Selection Mode<\/a><\/li><\/ul><\/li><li><a href=\"#\ud83d\uddfa\ufe0f-mapping-gateway-sip-settings-callee-and-caller-field-selection\">\ud83d\uddfa\ufe0f Mapping Gateway SIP Settings: Callee and Caller Field Selection<\/a><ul><li><a href=\"#\ud83d\udcde-callee-number-field-selection\">\ud83d\udcde Callee Number Field Selection<\/a><\/li><li><a href=\"#\ud83d\udcde-caller-number-field-selection\">\ud83d\udcde Caller Number Field Selection<\/a><\/li><\/ul><\/li><li><a href=\"#\ud83d\udd04-vos-3000-sip-routing-gateway-contact-complete-signal-flow\">\ud83d\udd04 VOS3000 SIP Routing Gateway Contact: Complete Signal Flow<\/a><\/li><li><a href=\"#\u2699\ufe0f-step-by-step-vos-3000-sip-routing-gateway-contact-configuration\">\u2699\ufe0f Step-by-Step VOS3000 SIP Routing Gateway Contact Configuration<\/a><ul><li><a href=\"#step-1-configure-global-ss-sip-routing-gateway-invite-use-contact-\ud83d\udccb\">Step 1: Configure Global SS_SIP_ROUTING_GATEWAY_INVITE_USE_CONTACT \ud83d\udccb<\/a><\/li><li><a href=\"#step-2-configure-routing-gateway-sip-settings-\ud83d\udce1\">Step 2: Configure Routing Gateway SIP Settings \ud83d\udce1<\/a><\/li><li><a href=\"#step-3-configure-mapping-gateway-sip-settings-\ud83d\uddfa\ufe0f\">Step 3: Configure Mapping Gateway SIP Settings \ud83d\uddfa\ufe0f<\/a><\/li><li><a href=\"#step-4-verify-with-sip-debug-\ud83d\udd0d\">Step 4: Verify with SIP Debug \ud83d\udd0d<\/a><\/li><\/ul><\/li><li><a href=\"#\ud83d\udcca-vos-3000-sip-routing-gateway-contact-when-to-enable-vs-disable\">\ud83d\udcca VOS3000 SIP Routing Gateway Contact: When to Enable vs. Disable<\/a><\/li><li><a href=\"#\ud83d\udccb-vos-3000-sip-routing-gateway-contact-complete-gateway-settings-reference\">\ud83d\udccb VOS3000 SIP Routing Gateway Contact: Complete Gateway Settings Reference<\/a><\/li><li><a href=\"#\ud83d\udcca-deployment-best-practices-by-gateway-type\">\ud83d\udcca Deployment Best Practices by Gateway Type<\/a><\/li><li><a href=\"#\ud83d\udee1\ufe0f-common-vos-3000-sip-routing-gateway-contact-problems-and-solutions\">\ud83d\udee1\ufe0f Common VOS3000 SIP Routing Gateway Contact Problems and Solutions<\/a><ul><li><a href=\"#\u274c-problem-1-calls-routed-to-wrong-number-after-prefix-conversion\">\u274c Problem 1: Calls Routed to Wrong Number After Prefix Conversion<\/a><\/li><li><a href=\"#\u274c-problem-2-gateway-rejects-invite-404-not-found\">\u274c Problem 2: Gateway Rejects INVITE \u2014 404 Not Found<\/a><\/li><li><a href=\"#\u274c-problem-3-cdr-shows-incorrect-original-number\">\u274c Problem 3: CDR Shows Incorrect Original Number<\/a><\/li><li><a href=\"#\u274c-problem-4-one-way-audio-after-enabling-contact-header-routing\">\u274c Problem 4: One-Way Audio After Enabling Contact Header Routing<\/a><\/li><\/ul><\/li><li><a href=\"#\ud83d\udca1-vos-3000-sip-routing-gateway-contact-configuration-checklist\">\ud83d\udca1 VOS3000 SIP Routing Gateway Contact Configuration Checklist<\/a><\/li><li><a href=\"#\u2753-frequently-asked-questions\">\u2753 Frequently Asked Questions<\/a><ul><li><a href=\"#\u2753-what-is-ss-sip-routing-gateway-invite-use-contact-in-vos-3000\">\u2753 What is SS_SIP_ROUTING_GATEWAY_INVITE_USE_CONTACT in VOS3000?<\/a><\/li><li><a href=\"#\u2753-when-should-i-enable-vos-3000-sip-routing-gateway-contact\">\u2753 When should I enable VOS3000 SIP routing gateway contact?<\/a><\/li><li><a href=\"#\u2753-what-is-the-difference-between-the-routing-gateway-contact-setting-and-the-mapping-gateway-callee-field\">\u2753 What is the difference between the Routing Gateway Contact setting and the Mapping Gateway Callee field?<\/a><\/li><li><a href=\"#\u2753-what-does-the-reply-address-socket-setting-do-in-vos-3000\">\u2753 What does the Reply address Socket setting do in VOS3000?<\/a><\/li><li><a href=\"#\u2753-how-does-the-request-address-setting-relate-to-the-contact-header\">\u2753 How does the Request address setting relate to the Contact header?<\/a><\/li><li><a href=\"#\u2753-can-i-configure-ss-sip-routing-gateway-invite-use-contact-per-gateway\">\u2753 Can I configure SS_SIP_ROUTING_GATEWAY_INVITE_USE_CONTACT per gateway?<\/a><\/li><li><a href=\"#\u2753-what-happens-to-the-to-field-when-vos-3000-sip-routing-gateway-contact-is-enabled\">\u2753 What happens to the To field when VOS3000 SIP routing gateway contact is enabled?<\/a><\/li><\/ul><\/li><li><a href=\"#\ud83d\udcda-related-resources\">\ud83d\udcda Related Resources &#8211; VOS3000 SIP Routing Gateway<\/a><\/li><li><a href=\"#\ud83d\udcde-need-call-center-setup-support\">\ud83d\udcde Need Professional VOS3000 Setup Support?<\/a><\/li><\/ul><\/li><\/ul><\/nav><\/div>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\ud83d\udd10-what-is-vos-3000-sip-routing-gateway-contact\">\ud83d\udd10 What Is VOS3000 SIP Routing Gateway Contact?<\/h2>\n\n\n\n<p>\ud83d\udcde The <strong>VOS3000 SIP routing gateway contact<\/strong> parameter controls how VOS3000 constructs the SIP INVITE message when sending calls to a routing gateway. Specifically, it determines whether the callee number should be extracted from the request-line and whether the original number should be preserved in the To field. \ud83d\udccb<\/p>\n\n\n\n<p>\ud83d\udccc According to the official VOS3000 V2.1.9.07 Manual, Table 4-3:<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><th class=\"has-text-align-left\" data-align=\"left\">Attribute<\/th><th class=\"has-text-align-left\" data-align=\"left\">Value<\/th><\/tr><tr><td>\ud83d\udccc Parameter Name<\/td><td>SS_SIP_ROUTING_GATEWAY_INVITE_USE_CONTACT<\/td><\/tr><tr><td>\ud83d\udd22 Default Value<\/td><td>Off<\/td><\/tr><tr><td>\ud83d\udcdd Description<\/td><td>Use number from request-line as callee and keep original number in To field when send invite to callee<\/td><\/tr><tr><td>\ud83d\udd00 Options<\/td><td>On \/ Off<\/td><\/tr><tr><td>\ud83d\udccd Navigation<\/td><td>Operation management \u2192 Softswitch management \u2192 Additional settings \u2192 SIP parameter<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p>\ud83d\udca1 <strong>Key insight:<\/strong> When this parameter is set to <strong>Off<\/strong> (default), VOS3000 follows the standard SIP RFC 3261 convention \u2014 the callee number in the INVITE is determined by the To header, and the request-line matches. When set to <strong>On<\/strong>, VOS3000 extracts the callee number from the <em>request-line<\/em> of the incoming SIP message and uses that for routing, while keeping the original number in the To field of the outbound INVITE. This is essential when upstream gateways manipulate the request-line during transit. \ud83d\udce1<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\ud83c\udfaf-why-vos-3000-sip-routing-gateway-contact-matters\">\ud83c\udfaf Why VOS3000 SIP Routing Gateway Contact Matters<\/h3>\n\n\n\n<p>\u26a0\ufe0f Understanding and correctly configuring this parameter is critical for several reasons:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\ud83d\udcde <strong>Number routing accuracy:<\/strong> If the callee number source does not match what the downstream gateway expects, calls may be routed to the wrong destination or rejected entirely<\/li>\n\n\n\n<li>\ud83d\udd04 <strong>To field preservation:<\/strong> Enabling this setting preserves the original dialed number in the To field, which is essential for billing, CDR accuracy, and troubleshooting<\/li>\n\n\n\n<li>\ud83d\udd17 <strong>Gateway compatibility:<\/strong> Some SIP gateways and carrier equipment extract the callee number from the request-line rather than the To header \u2014 this parameter ensures compatibility<\/li>\n\n\n\n<li>\ud83d\udcca <strong>Call flow integrity:<\/strong> Mismatched headers can cause call failures, one-way audio, or incorrect number display on the receiving end<\/li>\n\n\n\n<li>\ud83d\udee1\ufe0f <strong>Interoperability:<\/strong> Different vendors implement SIP differently; this parameter gives you the flexibility to adapt VOS3000 to various gateway behaviors<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\u2699\ufe0f-how-ss-sip-routing-gateway-invite-use-contact-works\">\u2699\ufe0f How SS_SIP_ROUTING_GATEWAY_INVITE_USE_CONTACT Works<\/h2>\n\n\n\n<p>\ud83d\udd04 To understand this parameter, you need to see how the SIP INVITE message changes based on the setting. Here is a text-based comparison of the two modes: \ud83d\udce1<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">\ud83d\udccb SIP INVITE Message Structure \u2014 SS_SIP_ROUTING_GATEWAY_INVITE_USE_CONTACT:\n\n\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\n\u2b07\ufe0f Mode: OFF (Default)\n\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\n\nINVITE sip:8801234567@gateway.example.com SIP\/2.0     \u2190 Request-Line\nVia: SIP\/2.0\/UDP 10.0.0.1:5060\nFrom: \"Caller\" &lt;sip:8801999888@vos3000.local&gt;;tag=abc\nTo: &lt;sip:8801234567@gateway.example.com&gt;             \u2190 Callee = To header\nContact: &lt;sip:8801999888@10.0.0.1:5060&gt;\nContent-Type: application\/sdp\n\n\ud83d\udccc Result: Callee number = 8801234567 (from To header)\n   Request-Line and To header contain the SAME number\n\n\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\n\u2b07\ufe0f Mode: ON\n\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\u2501\n\nINVITE sip:8801234567@gateway.example.com SIP\/2.0     \u2190 Request-Line (used for routing)\nVia: SIP\/2.0\/UDP 10.0.0.1:5060\nFrom: \"Caller\" &lt;sip:8801999888@vos3000.local&gt;;tag=abc\nTo: &lt;sip:ORIGINAL_NUMBER@gateway.example.com&gt;         \u2190 Original number PRESERVED\nContact: &lt;sip:8801999888@10.0.0.1:5060&gt;\nContent-Type: application\/sdp\n\n\ud83d\udccc Result: Callee number = 8801234567 (from Request-Line)\n   To field keeps the ORIGINAL number (before any manipulation)\n<\/pre>\n\n\n\n<p>\ud83d\udcca <strong>Critical distinction:<\/strong> When the parameter is <strong>On<\/strong>, the request-line contains the number that VOS3000 uses for actual routing (the callee number), while the To header retains the original dialed number before any prefix manipulation or routing transformation. This is extremely useful when VOS3000 applies prefix conversion rules \u2014 the gateway receives the routing number in the request-line but the original number remains in the To field for reference. \ud83c\udfaf<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\ud83d\udccb-per-gateway-sip-settings-reply-address-and-request-address\">\ud83d\udccb Per-Gateway SIP Settings: Reply Address and Request Address<\/h2>\n\n\n\n<p>\ud83d\udd17 Beyond the global SS_SIP_ROUTING_GATEWAY_INVITE_USE_CONTACT parameter, VOS3000 provides per-gateway SIP settings that control how reply and request signals are addressed. These settings are configured at the individual gateway level under <strong>Routing Gateway \u2192 Additional settings \u2192 Protocol \u2192 SIP<\/strong>. \ud83d\udee0\ufe0f<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\ud83d\udce8-reply-address-where-to-send-reply-signal\">\ud83d\udce8 Reply Address: Where to Send Reply Signal<\/h3>\n\n\n\n<p>\ud83d\udcec The <strong>Reply address<\/strong> setting determines where VOS3000 sends the reply signal after receiving a SIP request from the gateway. This is critical for ensuring SIP responses (such as 200 OK, 180 Ringing) reach the correct destination. \ud83d\udce1<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><th class=\"has-text-align-left\" data-align=\"left\">Option<\/th><th class=\"has-text-align-left\" data-align=\"left\">Description<\/th><th class=\"has-text-align-left\" data-align=\"left\">Recommendation<\/th><\/tr><tr><td>\ud83d\udfe2 Socket<\/td><td>Send reply to the source IP and port from which the SIP request was received<\/td><td>\u2705 Recommended \u2014 most reliable for NAT traversal<\/td><\/tr><tr><td>\ud83d\udd35 Via port<\/td><td>Send reply to the port specified in the Via header<\/td><td>\u26a0\ufe0f Use when gateway requires Via-based routing<\/td><\/tr><tr><td>\ud83d\udfe1 Via<\/td><td>Send reply to the address and port in the Via header<\/td><td>\u26a0\ufe0f Standard SIP behavior per RFC 3261<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p>\ud83d\udca1 <strong>Best practice:<\/strong> The <strong>Socket<\/strong> option is recommended for the Reply address because it ensures SIP responses are sent back to the actual source of the request, which is critical for NAT traversal scenarios. For a deeper understanding of SIP signal flow, see our <a href=\"https:\/\/multahost.com\/blog\/vos3000-sip-call-flow\/\">VOS3000 SIP call flow<\/a> guide. \ud83d\udcd6<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\ud83d\udce4-request-address-where-to-send-request-signal\">\ud83d\udce4 Request Address: Where to Send Request Signal<\/h3>\n\n\n\n<p>\ud83d\udce8 The <strong>Request address<\/strong> setting determines where VOS3000 sends the request signal after a call is established. This setting directly relates to the <strong>VOS3000 SIP routing gateway contact<\/strong> concept because it controls whether VOS3000 uses the Contact header or socket information for subsequent requests. \ud83d\udd27<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><th class=\"has-text-align-left\" data-align=\"left\">Option<\/th><th class=\"has-text-align-left\" data-align=\"left\">Description<\/th><th class=\"has-text-align-left\" data-align=\"left\">Recommendation<\/th><\/tr><tr><td>\ud83d\udfe2 Socket<\/td><td>Send request to the source IP and port from which the SIP request was received<\/td><td>\u2705 Recommended \u2014 most reliable<\/td><\/tr><tr><td>\ud83d\udd35 Contact Port<\/td><td>Send request to the port specified in the Contact header<\/td><td>\u26a0\ufe0f Use when gateway advertises a specific Contact port<\/td><\/tr><tr><td>\ud83d\udfe1 Contact<\/td><td>Send request to the full address in the Contact header<\/td><td>\u26a0\ufe0f Standard SIP per RFC 3261<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p>\ud83d\udd27 <strong>How this relates to the Contact header:<\/strong> The Request address setting determines how VOS3000 uses the <em>Contact<\/em> header for subsequent in-dialog requests (such as re-INVITE or BYE). When set to <strong>Contact<\/strong>, VOS3000 follows the SIP standard and sends requests to the URI in the Contact header. When set to <strong>Socket<\/strong>, VOS3000 uses the source socket address instead \u2014 which can be more reliable in NAT scenarios. This is especially important when combined with SS_SIP_ROUTING_GATEWAY_INVITE_USE_CONTACT. \ud83d\udce1<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\ud83d\udc64-peer-number-information-caller-selection-mode\">\ud83d\udc64 Peer Number Information: Caller Selection Mode<\/h3>\n\n\n\n<p>\ud83d\udccb The <strong>Peer number information<\/strong> setting in the Routing Gateway SIP configuration determines how VOS3000 selects the caller number from incoming SIP signals. This works in conjunction with the Contact and request-line settings to ensure proper number identification for both caller and callee. \ud83c\udfaf<\/p>\n\n\n\n<p>\ud83d\udcde For complete gateway configuration details, see our <a href=\"https:\/\/multahost.com\/blog\/vos3000-gateway-configuration-routing-mapping\/\">VOS3000 gateway configuration routing mapping<\/a> guide. \ud83d\udd27<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\ud83d\uddfa\ufe0f-mapping-gateway-sip-settings-callee-and-caller-field-selection\">\ud83d\uddfa\ufe0f Mapping Gateway SIP Settings: Callee and Caller Field Selection<\/h2>\n\n\n\n<p>\ud83d\udd04 While the Routing Gateway settings control how VOS3000 <em>sends<\/em> INVITE messages, the <strong>Mapping Gateway<\/strong> settings control how VOS3000 <em>receives and interprets<\/em> incoming SIP signals. These are configured at <strong>Mapping Gateway \u2192 Additional settings \u2192 Protocol \u2192 SIP<\/strong>. \ud83d\udce1<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\ud83d\udcde-callee-number-field-selection\">\ud83d\udcde Callee Number Field Selection<\/h3>\n\n\n\n<p>\ud83c\udfaf The Mapping Gateway provides a setting to determine which SIP field VOS3000 uses to extract the <strong>callee number<\/strong> from incoming INVITE messages. This is the <em>inbound<\/em> counterpart to SS_SIP_ROUTING_GATEWAY_INVITE_USE_CONTACT: \ud83d\udccb<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><th class=\"has-text-align-left\" data-align=\"left\">Callee Source Field<\/th><th class=\"has-text-align-left\" data-align=\"left\">Description<\/th><th class=\"has-text-align-left\" data-align=\"left\">When to Use<\/th><\/tr><tr><td>\ud83d\udce9 <strong>To<\/strong><\/td><td>Extract callee number from the SIP To header<\/td><td>\u2705 Default \u2014 standard SIP behavior, use when gateways follow RFC 3261<\/td><\/tr><tr><td>\ud83d\udce8 <strong>Request-Line<\/strong><\/td><td>Extract callee number from the SIP Request-Line<\/td><td>\u26a0\ufe0f Use when upstream gateway modifies the request-line with the routing number<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p>\ud83d\udca1 <strong>Critical relationship:<\/strong> The Mapping Gateway callee setting (To vs Request-Line) is the <em>receiving<\/em> side of the same concept that SS_SIP_ROUTING_GATEWAY_INVITE_USE_CONTACT handles on the <em>sending<\/em> side. If an upstream system sends INVITE messages where the request-line contains the routing number (different from the To header), you must configure the Mapping Gateway to extract the callee from the Request-Line. Similarly, if your downstream gateway expects the callee in the request-line, enable SS_SIP_ROUTING_GATEWAY_INVITE_USE_CONTACT. \ud83d\udd04<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\ud83d\udcde-caller-number-field-selection\">\ud83d\udcde Caller Number Field Selection<\/h3>\n\n\n\n<p>\ud83d\udc64 The Mapping Gateway also provides settings for extracting the <strong>caller number<\/strong> from incoming SIP signals: \ud83d\udccb<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><th class=\"has-text-align-left\" data-align=\"left\">Caller Source Field<\/th><th class=\"has-text-align-left\" data-align=\"left\">Description<\/th><th class=\"has-text-align-left\" data-align=\"left\">When to Use<\/th><\/tr><tr><td>\ud83d\udce9 <strong>From<\/strong><\/td><td>Extract caller number from the SIP From header<\/td><td>\u2705 Default \u2014 standard SIP behavior<\/td><\/tr><tr><td>\ud83c\udd94 <strong>Remote-Party-ID<\/strong><\/td><td>Extract caller number from the Remote-Party-ID header<\/td><td>\u26a0\ufe0f Use when upstream gateway sends caller ID in RPID header<\/td><\/tr><tr><td>\ud83d\udda5\ufe0f <strong>Display<\/strong><\/td><td>Extract caller number from the Display name portion of the From header<\/td><td>\u26a0\ufe0f Use when caller ID is in the display name, not the URI<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p>\ud83d\udcde <strong>Practical tip:<\/strong> When connecting to carrier gateways that manipulate caller ID through P-Asserted-Identity or Remote-Party-ID headers, configure the Mapping Gateway caller field accordingly. For more on caller ID management, see our <a href=\"https:\/\/multahost.com\/blog\/callee-rewrite-rule-prefix-conversion-clients-vendor-prefix-settings-in-vos3000\/\">VOS3000 callee rewrite rule and prefix conversion<\/a> guide. \ud83d\udd27<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\ud83d\udd04-vos-3000-sip-routing-gateway-contact-complete-signal-flow\">\ud83d\udd04 VOS3000 SIP Routing Gateway Contact: Complete Signal Flow<\/h2>\n\n\n\n<p>\ud83d\udcca To fully understand how SS_SIP_ROUTING_GATEWAY_INVITE_USE_CONTACT interacts with per-gateway settings, here is a complete signal flow diagram: \ud83d\udce1<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">\ud83d\udd04 VOS3000 SIP Routing Gateway Contact \u2014 Complete Signal Flow:\n\n\u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510         \u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510         \u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510\n\u2502  Calling      \u2502  SIP    \u2502   VOS3000    \u2502  SIP    \u2502  Routing     \u2502\n\u2502  Endpoint     \u2502 INVITE  \u2502  Softswitch  \u2502 INVITE  \u2502  Gateway     \u2502\n\u2514\u2500\u2500\u2500\u2500\u2500\u2500\u252c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518         \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u252c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518         \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u252c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518\n       \u2502                        \u2502                         \u2502\n       \u2502\u2500\u2500\u2500 INVITE \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u25ba\u2502                         \u2502\n       \u2502   To: 8801234567       \u2502                         \u2502\n       \u2502   From: 8801999888     \u2502                         \u2502\n       \u2502                        \u2502                         \u2502\n       \u2502   \ud83d\udccb Mapping Gateway:  \u2502                         \u2502\n       \u2502   Callee from: To\/     \u2502                         \u2502\n       \u2502   Request-Line         \u2502                         \u2502\n       \u2502   Caller from: From\/   \u2502                         \u2502\n       \u2502   RPID\/Display         \u2502                         \u2502\n       \u2502                        \u2502                         \u2502\n       \u2502                        \u2502 \ud83d\udce4 SS_SIP_ROUTING_      \u2502\n       \u2502                        \u2502 GATEWAY_INVITE_USE_     \u2502\n       \u2502                        \u2502 CONTACT = ?             \u2502\n       \u2502                        \u2502                         \u2502\n       \u2502                        \u2502\u2500\u2500\u2500 INVITE \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u25ba\u2502\n       \u2502                        \u2502   \u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510  \u2502\n       \u2502                        \u2502   \u2502 OFF (default):   \u2502  \u2502\n       \u2502                        \u2502   \u2502 Request-Line:    \u2502  \u2502\n       \u2502                        \u2502   \u2502   8801234567     \u2502  \u2502\n       \u2502                        \u2502   \u2502 To: 8801234567   \u2502  \u2502\n       \u2502                        \u2502   \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518  \u2502\n       \u2502                        \u2502   \u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510  \u2502\n       \u2502                        \u2502   \u2502 ON:              \u2502  \u2502\n       \u2502                        \u2502   \u2502 Request-Line:    \u2502  \u2502\n       \u2502                        \u2502   \u2502   8801234567     \u2502  \u2502\n       \u2502                        \u2502   \u2502 To: ORIGINAL     \u2502  \u2502\n       \u2502                        \u2502   \u2502   (preserved)    \u2502  \u2502\n       \u2502                        \u2502   \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518  \u2502\n       \u2502                        \u2502                         \u2502\n       \u2502                        \u2502 \ud83d\udce8 Reply address:       \u2502\n       \u2502                        \u2502   Socket \/ Via port \/ Via\u2502\n       \u2502                        \u2502 \ud83d\udce4 Request address:     \u2502\n       \u2502                        \u2502   Socket \/ Contact Port \u2502\n       \u2502                        \u2502   \/ Contact             \u2502\n       \u2502                        \u2502                         \u2502\n       \u2502\u25c4\u2500\u2500 200 OK \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2502\u25c4\u2500\u2500 200 OK \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2502\n       \u2502                        \u2502                         \u2502\n       \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2534\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518\n<\/pre>\n\n\n\n<p>\ud83c\udfaf <strong>Key takeaway:<\/strong> The Mapping Gateway settings control what VOS3000 reads <em>from incoming<\/em> INVITE messages, while SS_SIP_ROUTING_GATEWAY_INVITE_USE_CONTACT and the per-gateway Reply\/Request address settings control what VOS3000 writes <em>into outgoing<\/em> INVITE messages. For a comprehensive understanding of SIP session management, see our <a href=\"https:\/\/multahost.com\/blog\/vos3000-sip-session\/\">VOS3000 SIP session<\/a> guide. \ud83d\udcd6<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\u2699\ufe0f-step-by-step-vos-3000-sip-routing-gateway-contact-configuration\">\u2699\ufe0f Step-by-Step VOS3000 SIP Routing Gateway Contact Configuration<\/h2>\n\n\n\n<p>\ud83d\udd27 Follow these steps to configure the VOS3000 SIP routing gateway contact and related settings on your system:<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"step-1-configure-global-ss-sip-routing-gateway-invite-use-contact-\ud83d\udccb\">Step 1: Configure Global SS_SIP_ROUTING_GATEWAY_INVITE_USE_CONTACT \ud83d\udccb<\/h3>\n\n\n\n<ol class=\"wp-block-list\">\n<li>\ud83d\udd10 Log in to VOS3000 Client with administrator credentials<\/li>\n\n\n\n<li>\ud83d\udccc Navigate: <strong>Operation management \u2192 Softswitch management \u2192 Additional settings \u2192 SIP parameter<\/strong><\/li>\n\n\n\n<li>\ud83d\udd0d Locate <strong>SS_SIP_ROUTING_GATEWAY_INVITE_USE_CONTACT<\/strong> in the parameter list<\/li>\n\n\n\n<li>\u270f\ufe0f Set the value:\n<ul class=\"wp-block-list\">\n<li>\ud83d\udfe2 <strong>Off<\/strong> (default) \u2014 Standard SIP behavior; callee from To header<\/li>\n\n\n\n<li>\ud83d\udd35 <strong>On<\/strong> \u2014 Use request-line number as callee; preserve original in To field<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li>\ud83d\udcbe Save and apply the changes<\/li>\n<\/ol>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"step-2-configure-routing-gateway-sip-settings-\ud83d\udce1\">Step 2: Configure Routing Gateway SIP Settings \ud83d\udce1<\/h3>\n\n\n\n<ol class=\"wp-block-list\">\n<li>\ud83d\udccc Navigate: <strong>Operation management \u2192 Softswitch management \u2192 Routing gateway<\/strong><\/li>\n\n\n\n<li>\ud83d\udd0d Select the target routing gateway<\/li>\n\n\n\n<li>\ud83d\udd27 Go to <strong>Additional settings \u2192 Protocol \u2192 SIP<\/strong><\/li>\n\n\n\n<li>\u2699\ufe0f Configure the following settings:\n<ul class=\"wp-block-list\">\n<li>\ud83d\udcec <strong>Reply address:<\/strong> Socket (recommended) \/ Via port \/ Via<\/li>\n\n\n\n<li>\ud83d\udce4 <strong>Request address:<\/strong> Socket (recommended) \/ Contact Port \/ Contact<\/li>\n\n\n\n<li>\ud83d\udc64 <strong>Peer number information:<\/strong> Set caller number selection mode<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li>\ud83d\udcbe Save gateway settings<\/li>\n<\/ol>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"step-3-configure-mapping-gateway-sip-settings-\ud83d\uddfa\ufe0f\">Step 3: Configure Mapping Gateway SIP Settings \ud83d\uddfa\ufe0f<\/h3>\n\n\n\n<ol class=\"wp-block-list\">\n<li>\ud83d\udccc Navigate: <strong>Operation management \u2192 Softswitch management \u2192 Mapping gateway<\/strong><\/li>\n\n\n\n<li>\ud83d\udd0d Select the target mapping gateway<\/li>\n\n\n\n<li>\ud83d\udd27 Go to <strong>Additional settings \u2192 Protocol \u2192 SIP<\/strong><\/li>\n\n\n\n<li>\u2699\ufe0f Configure the following settings:\n<ul class=\"wp-block-list\">\n<li>\ud83d\udcde <strong>Callee:<\/strong> To \/ Request-Line \u2014 determines which field VOS3000 reads for the callee number<\/li>\n\n\n\n<li>\ud83d\udc64 <strong>Caller:<\/strong> From \/ Remote-Party-ID \/ Display \u2014 determines which field VOS3000 reads for the caller number<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li>\ud83d\udcbe Save mapping gateway settings<\/li>\n<\/ol>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"step-4-verify-with-sip-debug-\ud83d\udd0d\">Step 4: Verify with SIP Debug \ud83d\udd0d<\/h3>\n\n\n\n<p>\ud83d\udcdd After configuration, verify the Contact header behavior by monitoring the SIP INVITE flow. Use the SIP debug tools to confirm that the request-line and To header are populated correctly. For comprehensive debugging techniques, see our <a href=\"https:\/\/multahost.com\/blog\/vos3000-sip-debug-guide\/\">VOS3000 SIP debug guide<\/a>. \ud83d\udd27<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\ud83d\udcca-vos-3000-sip-routing-gateway-contact-when-to-enable-vs-disable\">\ud83d\udcca VOS3000 SIP Routing Gateway Contact: When to Enable vs. Disable<\/h2>\n\n\n\n<p>\ud83c\udfaf The decision to enable or disable SS_SIP_ROUTING_GATEWAY_INVITE_USE_CONTACT depends on your specific gateway interoperability requirements. Here is a detailed comparison: \ud83d\udca1<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><th class=\"has-text-align-left\" data-align=\"left\">Aspect<\/th><th class=\"has-text-align-left\" data-align=\"left\">Off (Default)<\/th><th class=\"has-text-align-left\" data-align=\"left\">On<\/th><\/tr><tr><td>\ud83d\udccc Callee Number Source<\/td><td>To header<\/td><td>Request-Line<\/td><\/tr><tr><td>\ud83d\udd04 To Field Content<\/td><td>Same as request-line callee<\/td><td>Original number (preserved)<\/td><\/tr><tr><td>\ud83d\udcde Request-Line<\/td><td>Matches To header<\/td><td>Contains routing number<\/td><\/tr><tr><td>\ud83d\udee1\ufe0f RFC 3261 Compliance<\/td><td>\u2705 Full compliance<\/td><td>\u26a0\ufe0f Modified behavior<\/td><\/tr><tr><td>\ud83d\udd27 Best For<\/td><td>Standard SIP gateways, carriers that follow RFC 3261<\/td><td>Gateways that read callee from request-line, prefix conversion scenarios<\/td><\/tr><tr><td>\ud83d\udcca Billing Impact<\/td><td>CDR shows final routing number<\/td><td>CDR can preserve original dialed number<\/td><\/tr><tr><td>\ud83d\udd17 Compatibility<\/td><td>Broad \u2014 works with most gateways<\/td><td>Specific \u2014 needed for certain gateway types<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p>\ud83d\udca1 <strong>Decision rule:<\/strong> Keep the default <strong>Off<\/strong> unless you encounter a specific gateway that routes based on the request-line callee number instead of the To header. Most modern SIP gateways follow RFC 3261 and use the To header. However, some legacy systems or carrier equipment may depend on the request-line \u2014 in those cases, enable the parameter to <strong>On<\/strong>. For help identifying which mode your gateway requires, contact us on WhatsApp at <strong>+8801911119966<\/strong>. \ud83d\udcde<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\ud83d\udccb-vos-3000-sip-routing-gateway-contact-complete-gateway-settings-reference\">\ud83d\udccb VOS3000 SIP Routing Gateway Contact: Complete Gateway Settings Reference<\/h2>\n\n\n\n<p>\ud83d\udcca Here is the complete reference for all per-gateway SIP settings related to the VOS3000 SIP routing gateway contact configuration: \ud83d\udcd6<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><th class=\"has-text-align-left\" data-align=\"left\">Setting<\/th><th class=\"has-text-align-left\" data-align=\"left\">Location<\/th><th class=\"has-text-align-left\" data-align=\"left\">Options<\/th><th class=\"has-text-align-left\" data-align=\"left\">Recommended<\/th><\/tr><tr><td>\ud83d\udcec Reply address<\/td><td>Routing Gateway \u2192 Protocol \u2192 SIP<\/td><td>Socket \/ Via port \/ Via<\/td><td>\u2705 Socket<\/td><\/tr><tr><td>\ud83d\udce4 Request address<\/td><td>Routing Gateway \u2192 Protocol \u2192 SIP<\/td><td>Socket \/ Contact Port \/ Contact<\/td><td>\u2705 Socket<\/td><\/tr><tr><td>\ud83d\udc64 Peer number info<\/td><td>Routing Gateway \u2192 Protocol \u2192 SIP<\/td><td>Caller selection mode<\/td><td>Depends on gateway<\/td><\/tr><tr><td>\ud83d\udcde Callee field<\/td><td>Mapping Gateway \u2192 Protocol \u2192 SIP<\/td><td>To \/ Request-Line<\/td><td>To (default)<\/td><\/tr><tr><td>\ud83d\udc64 Caller field<\/td><td>Mapping Gateway \u2192 Protocol \u2192 SIP<\/td><td>From \/ Remote-Party-ID \/ Display<\/td><td>From (default)<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p>\ud83d\udd27 For complete documentation on all SIP parameters, see our <a href=\"https:\/\/multahost.com\/blog\/vos3000-parameter-description\/\">VOS3000 parameter description<\/a> reference. \ud83d\udcd6<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\ud83d\udcca-deployment-best-practices-by-gateway-type\">\ud83d\udcca Deployment Best Practices by Gateway Type<\/h2>\n\n\n\n<p>\ud83c\udfaf Different gateway types require different configurations for the VOS3000 SIP routing gateway contact settings. Here are recommended configurations based on common deployment scenarios: \ud83d\udca1<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><th class=\"has-text-align-left\" data-align=\"left\">Gateway Type<\/th><th class=\"has-text-align-left\" data-align=\"left\">SS_SIP_ROUTING_GATEWAY_INVITE_USE_CONTACT<\/th><th class=\"has-text-align-left\" data-align=\"left\">Callee Field (Mapping)<\/th><th class=\"has-text-align-left\" data-align=\"left\">Reply \/ Request Address<\/th><\/tr><tr><td>\ud83c\udfe2 Standard SIP carrier<\/td><td>Off (default)<\/td><td>To<\/td><td>Socket \/ Socket<\/td><\/tr><tr><td>\ud83d\udd04 Legacy gateway (request-line routing)<\/td><td>On<\/td><td>Request-Line<\/td><td>Socket \/ Socket<\/td><\/tr><tr><td>\ud83d\udcde PSTN gateway (prefix conversion)<\/td><td>On<\/td><td>Request-Line<\/td><td>Socket \/ Contact<\/td><\/tr><tr><td>\ud83d\udce1 NAT-traversed gateway<\/td><td>Off (default)<\/td><td>To<\/td><td>Socket \/ Socket<\/td><\/tr><tr><td>\ud83c\udf10 Wholesale carrier (multiple prefixes)<\/td><td>On<\/td><td>Request-Line<\/td><td>Socket \/ Contact<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p>\ud83d\udca1 <strong>Key pattern:<\/strong> Enable SS_SIP_ROUTING_GATEWAY_INVITE_USE_CONTACT (<strong>On<\/strong>) when your gateway performs prefix conversion and you need the original number preserved in the To field while the routing number goes in the request-line. For more on prefix conversion, see our <a href=\"https:\/\/multahost.com\/blog\/vos3000-routing-optimization\/\">VOS3000 routing optimization<\/a> guide. \ud83d\udd27<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\ud83d\udee1\ufe0f-common-vos-3000-sip-routing-gateway-contact-problems-and-solutions\">\ud83d\udee1\ufe0f Common VOS3000 SIP Routing Gateway Contact Problems and Solutions<\/h2>\n\n\n\n<p>\u26a0\ufe0f Misconfigured Contact header settings can cause a range of call routing issues. Here are the most common problems and their solutions:<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\u274c-problem-1-calls-routed-to-wrong-number-after-prefix-conversion\">\u274c Problem 1: Calls Routed to Wrong Number After Prefix Conversion<\/h3>\n\n\n\n<p>\ud83d\udd0d <strong>Symptom:<\/strong> VOS3000 applies a prefix conversion rule, but the downstream gateway still routes the call using the original number instead of the converted number.<\/p>\n\n\n\n<p>\ud83d\udca1 <strong>Cause:<\/strong> SS_SIP_ROUTING_GATEWAY_INVITE_USE_CONTACT is set to Off, so both the request-line and To header contain the original number. The gateway reads the To header and ignores the prefix conversion.<\/p>\n\n\n\n<p>\u2705 <strong>Solutions:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\ud83d\udd27 Enable SS_SIP_ROUTING_GATEWAY_INVITE_USE_CONTACT to <strong>On<\/strong><\/li>\n\n\n\n<li>\ud83d\udcde This puts the converted (routing) number in the request-line while preserving the original in the To field<\/li>\n\n\n\n<li>\ud83d\udcca Verify with SIP debug that the request-line contains the correct routing number<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\u274c-problem-2-gateway-rejects-invite-404-not-found\">\u274c Problem 2: Gateway Rejects INVITE \u2014 404 Not Found<\/h3>\n\n\n\n<p>\ud83d\udd0d <strong>Symptom:<\/strong> Downstream gateway returns 404 Not Found for calls that should be routable, even though the callee number exists in the gateway&#8217;s routing table.<\/p>\n\n\n\n<p>\ud83d\udca1 <strong>Cause:<\/strong> The gateway extracts the callee number from a different header than what VOS3000 is populating. For example, the gateway reads the request-line but VOS3000 is only populating the To header (parameter set to Off).<\/p>\n\n\n\n<p>\u2705 <strong>Solutions:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\ud83d\udd27 Confirm which SIP field the downstream gateway uses for callee identification<\/li>\n\n\n\n<li>\ud83d\udccb If the gateway reads the request-line, enable SS_SIP_ROUTING_GATEWAY_INVITE_USE_CONTACT<\/li>\n\n\n\n<li>\ud83d\udce1 Check the gateway documentation or contact the carrier for their header requirements<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\u274c-problem-3-cdr-shows-incorrect-original-number\">\u274c Problem 3: CDR Shows Incorrect Original Number<\/h3>\n\n\n\n<p>\ud83d\udd0d <strong>Symptom:<\/strong> Call Detail Records show the routing number (with prefix) instead of the original dialed number, making billing reconciliation difficult.<\/p>\n\n\n\n<p>\ud83d\udca1 <strong>Cause:<\/strong> SS_SIP_ROUTING_GATEWAY_INVITE_USE_CONTACT is Off, so the To header always contains the same number as the request-line \u2014 no original number is preserved.<\/p>\n\n\n\n<p>\u2705 <strong>Solutions:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\ud83d\udd04 Enable SS_SIP_ROUTING_GATEWAY_INVITE_USE_CONTACT to <strong>On<\/strong> \u2014 this preserves the original number in the To field<\/li>\n\n\n\n<li>\ud83d\udcca CDR systems can then read the original number from the To field for billing accuracy<\/li>\n\n\n\n<li>\ud83d\udcde For billing system configuration, see our <a href=\"https:\/\/multahost.com\/blog\/vos3000-billing-system\/\">VOS3000 billing system<\/a> guide<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\u274c-problem-4-one-way-audio-after-enabling-contact-header-routing\">\u274c Problem 4: One-Way Audio After Enabling Contact Header Routing<\/h3>\n\n\n\n<p>\ud83d\udd0d <strong>Symptom:<\/strong> After enabling SS_SIP_ROUTING_GATEWAY_INVITE_USE_CONTACT, calls connect but audio only flows in one direction.<\/p>\n\n\n\n<p>\ud83d\udca1 <strong>Cause:<\/strong> The Request address setting is configured to use Contact or Contact Port, and the Contact header in the gateway&#8217;s 200 OK response points to an incorrect or unreachable address.<\/p>\n\n\n\n<p>\u2705 <strong>Solutions:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\ud83d\udd27 Change the Request address to <strong>Socket<\/strong> \u2014 this ensures subsequent requests go to the actual source IP:port<\/li>\n\n\n\n<li>\ud83d\udce1 Verify the Contact header in the gateway&#8217;s responses using SIP debug<\/li>\n\n\n\n<li>\ud83d\udee0\ufe0f If the gateway is behind NAT, Socket-based routing is more reliable than Contact-based routing<\/li>\n\n\n\n<li>\ud83d\udd0d For detailed troubleshooting steps, see our <a href=\"https:\/\/multahost.com\/blog\/vos3000-troubleshooting-guide-2026\/\">VOS3000 troubleshooting guide<\/a><\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\ud83d\udca1-vos-3000-sip-routing-gateway-contact-configuration-checklist\">\ud83d\udca1 VOS3000 SIP Routing Gateway Contact Configuration Checklist<\/h2>\n\n\n\n<p>\u2705 Use this checklist when deploying or tuning your VOS3000 SIP routing gateway contact settings:<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><th class=\"has-text-align-left\" data-align=\"left\">Check<\/th><th class=\"has-text-align-left\" data-align=\"left\">Action<\/th><th class=\"has-text-align-left\" data-align=\"left\">Status<\/th><\/tr><tr><td>\ud83d\udccc 1<\/td><td>Determine if downstream gateway reads callee from To or Request-Line<\/td><td>\u2610<\/td><\/tr><tr><td>\ud83d\udccc 2<\/td><td>Set SS_SIP_ROUTING_GATEWAY_INVITE_USE_CONTACT to On if gateway uses Request-Line<\/td><td>\u2610<\/td><\/tr><tr><td>\ud83d\udccc 3<\/td><td>Configure Routing Gateway Reply address (Socket recommended)<\/td><td>\u2610<\/td><\/tr><tr><td>\ud83d\udccc 4<\/td><td>Configure Routing Gateway Request address (Socket recommended for NAT)<\/td><td>\u2610<\/td><\/tr><tr><td>\ud83d\udccc 5<\/td><td>Configure Mapping Gateway Callee field (To or Request-Line)<\/td><td>\u2610<\/td><\/tr><tr><td>\ud83d\udccc 6<\/td><td>Configure Mapping Gateway Caller field (From, Remote-Party-ID, or Display)<\/td><td>\u2610<\/td><\/tr><tr><td>\ud83d\udccc 7<\/td><td>Test with SIP debug \u2014 verify INVITE header fields match expected values<\/td><td>\u2610<\/td><\/tr><tr><td>\ud83d\udccc 8<\/td><td>Verify CDR records show correct callee number for billing<\/td><td>\u2610<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p>\ud83d\udcde Need help configuring your gateway Contact header settings? Contact our VOS3000 experts on WhatsApp at <strong>+8801911119966<\/strong> for personalized assistance. \ud83d\udd27<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\u2753-frequently-asked-questions\">\u2753 Frequently Asked Questions<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\u2753-what-is-ss-sip-routing-gateway-invite-use-contact-in-vos-3000\">\u2753 What is SS_SIP_ROUTING_GATEWAY_INVITE_USE_CONTACT in VOS3000?<\/h3>\n\n\n\n<p>\ud83d\udccb <strong>SS_SIP_ROUTING_GATEWAY_INVITE_USE_CONTACT<\/strong> is a VOS3000 SIP parameter that controls how the callee number is placed in outbound INVITE messages to routing gateways. When set to <strong>Off<\/strong> (default), VOS3000 follows standard SIP behavior where the To header and request-line contain the same callee number. When set to <strong>On<\/strong>, VOS3000 uses the number from the request-line as the callee for routing and keeps the original number in the To field. This is essential for gateways that read the callee from the request-line rather than the To header. \ud83d\udd27<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\u2753-when-should-i-enable-vos-3000-sip-routing-gateway-contact\">\u2753 When should I enable VOS3000 SIP routing gateway contact?<\/h3>\n\n\n\n<p>\ud83d\udd04 Enable SS_SIP_ROUTING_GATEWAY_INVITE_USE_CONTACT (<strong>On<\/strong>) when your downstream routing gateway extracts the callee number from the SIP request-line instead of the To header. This is common with legacy PSTN gateways, gateways that perform number manipulation, and carrier equipment that routes based on the INVITE request-line. You should also enable it when you apply prefix conversion rules and need the original dialed number preserved in the To field for billing and CDR accuracy. \ud83d\udce1<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\u2753-what-is-the-difference-between-the-routing-gateway-contact-setting-and-the-mapping-gateway-callee-field\">\u2753 What is the difference between the Routing Gateway Contact setting and the Mapping Gateway Callee field?<\/h3>\n\n\n\n<p>\ud83d\udcca These settings control opposite directions of SIP signaling. <strong>SS_SIP_ROUTING_GATEWAY_INVITE_USE_CONTACT<\/strong> (Routing Gateway) controls what VOS3000 <em>writes<\/em> into outbound INVITE messages \u2014 it determines whether the callee comes from the request-line and whether the To field preserves the original number. The <strong>Mapping Gateway Callee field<\/strong> (To \/ Request-Line) controls what VOS3000 <em>reads<\/em> from inbound INVITE messages \u2014 it determines which SIP field VOS3000 uses to extract the callee number from incoming calls. They work together to ensure proper number handling in both directions. \ud83d\udd04<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\u2753-what-does-the-reply-address-socket-setting-do-in-vos-3000\">\u2753 What does the Reply address Socket setting do in VOS3000?<\/h3>\n\n\n\n<p>\ud83d\udcec The <strong>Reply address<\/strong> setting in the Routing Gateway SIP configuration determines where VOS3000 sends SIP response messages (such as 200 OK, 180 Ringing, 403 Forbidden) after receiving a request from the gateway. When set to <strong>Socket<\/strong> (recommended), VOS3000 sends replies to the source IP address and port of the incoming SIP request. When set to <strong>Via<\/strong>, it uses the address in the Via header. When set to <strong>Via port<\/strong>, it uses the port from the Via header. The Socket option is most reliable for NAT traversal scenarios. \ud83d\udee1\ufe0f<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\u2753-how-does-the-request-address-setting-relate-to-the-contact-header\">\u2753 How does the Request address setting relate to the Contact header?<\/h3>\n\n\n\n<p>\ud83d\udce4 The <strong>Request address<\/strong> setting controls where VOS3000 sends in-dialog SIP requests (like re-INVITE or BYE) after call establishment. When set to <strong>Contact<\/strong>, VOS3000 sends requests to the full URI in the Contact header of the gateway&#8217;s response. When set to <strong>Contact Port<\/strong>, it uses only the port from the Contact header. When set to <strong>Socket<\/strong> (recommended), it sends to the source IP:port of the received signal. This is closely related to the VOS3000 SIP routing gateway contact behavior because it determines how the Contact header is used for subsequent signaling. \ud83d\udd27<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\u2753-can-i-configure-ss-sip-routing-gateway-invite-use-contact-per-gateway\">\u2753 Can I configure SS_SIP_ROUTING_GATEWAY_INVITE_USE_CONTACT per gateway?<\/h3>\n\n\n\n<p>\u2699\ufe0f The SS_SIP_ROUTING_GATEWAY_INVITE_USE_CONTACT parameter is a <em>global<\/em> SIP parameter configured at the system level under Operation management \u2192 Softswitch management \u2192 Additional settings \u2192 SIP parameter. However, the related per-gateway settings (Reply address, Request address, Peer number information for Routing Gateways; Callee and Caller field selection for Mapping Gateways) are configured at the individual gateway level. This means the base Contact header behavior is global, but the specific address routing and field selection can be customized per gateway. For system-level parameter documentation, see <a href=\"https:\/\/multahost.com\/blog\/vos3000-system-parameters\/\">VOS3000 system parameters<\/a>. \ud83d\udcd6<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"\u2753-what-happens-to-the-to-field-when-vos-3000-sip-routing-gateway-contact-is-enabled\">\u2753 What happens to the To field when VOS3000 SIP routing gateway contact is enabled?<\/h3>\n\n\n\n<p>\ud83d\udcde When SS_SIP_ROUTING_GATEWAY_INVITE_USE_CONTACT is set to <strong>On<\/strong>, VOS3000 preserves the <strong>original callee number<\/strong> in the To field of the outbound INVITE. The request-line contains the number that VOS3000 uses for actual routing (which may include prefix modifications or routing transformations), while the To field retains the original dialed number before any manipulation. This dual-number approach ensures that downstream gateways can route using the request-line number while billing and CDR systems can reference the original number from the To field. \ud83c\udfaf<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\ud83d\udcda-related-resources\">\ud83d\udcda Related Resources &#8211; VOS3000 SIP Routing Gateway<\/h2>\n\n\n\n<p>\ud83d\udd17 Explore these related VOS3000 guides for deeper understanding:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\ud83d\udcde <a href=\"https:\/\/multahost.com\/blog\/vos3000-sip-call-flow\/\">VOS3000 SIP Call Flow<\/a> \u2014 Complete SIP signal flow and message sequence<\/li>\n\n\n\n<li>\ud83d\udd04 <a href=\"https:\/\/multahost.com\/blog\/vos3000-sip-session\/\">VOS3000 SIP Session<\/a> \u2014 Session timer and call management configuration<\/li>\n\n\n\n<li>\ud83d\udd0d <a href=\"https:\/\/multahost.com\/blog\/vos3000-sip-debug-guide\/\">VOS3000 SIP Debug Guide<\/a> \u2014 Debug SIP signaling and troubleshoot header issues<\/li>\n\n\n\n<li>\ud83d\udccb <a href=\"https:\/\/multahost.com\/blog\/vos3000-parameter-description\/\">VOS3000 Parameter Description<\/a> \u2014 Complete parameter reference for all SIP settings<\/li>\n\n\n\n<li>\ud83d\udcca <a href=\"https:\/\/multahost.com\/blog\/vos3000-system-parameters\/\">VOS3000 System Parameters<\/a> \u2014 System-level parameter configuration guide<\/li>\n\n\n\n<li>\ud83d\udcde <a href=\"https:\/\/multahost.com\/blog\/vos3000-call-routing\/\">VOS3000 Call Routing<\/a> \u2014 Call routing configuration and optimization<\/li>\n\n\n\n<li>\ud83d\udd27 <a href=\"https:\/\/multahost.com\/blog\/vos3000-gateway-configuration-routing-mapping\/\">VOS3000 Gateway Configuration Routing Mapping<\/a> \u2014 Gateway setup and mapping configuration<\/li>\n\n\n\n<li>\ud83d\udcca <a href=\"https:\/\/multahost.com\/blog\/vos3000-gateway-route-prefix-billing\/\">VOS3000 Gateway Route Prefix Billing<\/a> \u2014 Prefix conversion and billing integration<\/li>\n\n\n\n<li>\ud83c\udfaf <a href=\"https:\/\/multahost.com\/blog\/vos3000-routing-optimization\/\">VOS3000 Routing Optimization<\/a> \u2014 Optimize routing with prefix and number manipulation<\/li>\n\n\n\n<li>\ud83d\udcd6 <a href=\"https:\/\/multahost.com\/blog\/vos3000-routing-guide\/\">VOS3000 Routing Guide<\/a> \u2014 Comprehensive routing configuration guide<\/li>\n\n\n\n<li>\ud83d\udd27 <a href=\"https:\/\/multahost.com\/blog\/callee-rewrite-rule-prefix-conversion-clients-vendor-prefix-settings-in-vos3000\/\">VOS3000 Callee Rewrite Rule Prefix Conversion<\/a> \u2014 Number rewrite and prefix conversion settings<\/li>\n\n\n\n<li>\ud83d\udee0\ufe0f <a href=\"https:\/\/multahost.com\/blog\/vos3000-troubleshooting-guide-2026\/\">VOS3000 Troubleshooting Guide<\/a> \u2014 Fix common SIP signaling and routing issues<\/li>\n\n\n\n<li>\ud83d\udce6 <a href=\"https:\/\/multahost.com\/blog\/vos3000-installation\/\">VOS3000 Installation<\/a> \u2014 Installation and initial setup guide<\/li>\n\n\n\n<li>\ud83d\udcb0 <a href=\"https:\/\/multahost.com\/blog\/vos3000-billing-system\/\">VOS3000 Billing System<\/a> \u2014 Billing configuration and CDR management<\/li>\n\n\n\n<li>\ud83c\udf10 <a href=\"https:\/\/www.vos3000.com\/downloads.php\" target=\"_blank\" rel=\"noopener\">VOS3000 Official Downloads<\/a> \u2014 Official software and documentation<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"\ud83d\udcde-need-call-center-setup-support\">\ud83d\udcde Need Professional VOS3000 Setup Support?<\/h2>\n\n\n\n<p>For professional VOS3000 installations and deployment, VOS3000 Server Rental Solution:<\/p>\n\n\n\n<p>\ud83d\udcf1 <strong>WhatsApp:<\/strong> <a href=\"https:\/\/wa.me\/8801911119966\" target=\"_blank\" rel=\"noopener\">+8801911119966<\/a><br>\ud83c\udf10 <strong>Website:<\/strong> <a href=\"https:\/\/www.vos3000.com\" target=\"_blank\" rel=\"noopener\">www.vos3000.com<\/a><br>\ud83c\udf10 <strong>Blog:<\/strong> <a href=\"https:\/\/multahost.com\/blog\">multahost.com\/blog<\/a><br>\ud83d\udce5 <strong>Downloads:<\/strong> <a href=\"https:\/\/www.vos3000.com\/downloads.php\" target=\"_blank\" rel=\"noopener\">VOS3000 Downloads<\/a><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td><img data-recalc-dims=\"1\" height=\"540\" width=\"809\" decoding=\"async\" src=\"https:\/\/i0.wp.com\/multahost.com\/blog\/wp-content\/uploads\/2026\/04\/VOS3000-SIP-Authentication-Retry-VOS3000-SIP-Early-Hangup-VOS3000-SIP-Session-Timer-Refresh-VOS3000-Non-Timer-Endpoint-Safety-VOS3000-SIP-NAT-Keepalive-4.png?resize=809%2C540\" alt=\"VOS3000 SIP Authentication Retry, VOS3000 SIP Early Hangup, VOS3000 SIP Session Timer Refresh, VOS3000 Non-Timer Endpoint Safety, VOS3000 SIP NAT Keepalive, VOS3000 SIP Resend Interval, VOS3000 SIP INVITE Timeout, VOS3000 SIP Call Progress Timeout, VOS3000 SIP Outbound Registration Parameters, VOS3000 SIP Privacy Header, VOS3000 SIP Routing Gateway Contact, VOS3000 SIP Publish Expire, VOS3000 SIP Display From, VOS3000 SIP Send Unregister\" title=\"\"><\/td><td><img data-recalc-dims=\"1\" height=\"540\" width=\"809\" decoding=\"async\" src=\"https:\/\/i0.wp.com\/multahost.com\/blog\/wp-content\/uploads\/2026\/04\/VOS3000-SIP-Authentication-Retry-VOS3000-SIP-Early-Hangup-VOS3000-SIP-Session-Timer-Refresh-VOS3000-Non-Timer-Endpoint-Safety-VOS3000-SIP-NAT-Keepalive-4.png?resize=809%2C540\" alt=\"VOS3000 SIP Authentication Retry, VOS3000 SIP Early Hangup, VOS3000 SIP Session Timer Refresh, VOS3000 Non-Timer Endpoint Safety, VOS3000 SIP NAT Keepalive, VOS3000 SIP Resend Interval, VOS3000 SIP INVITE Timeout, VOS3000 SIP Call Progress Timeout, VOS3000 SIP Outbound Registration Parameters, VOS3000 SIP Privacy Header, VOS3000 SIP Routing Gateway Contact, VOS3000 SIP Publish Expire, VOS3000 SIP Display From, VOS3000 SIP Send Unregister\" title=\"\"><\/td><td><img data-recalc-dims=\"1\" height=\"540\" width=\"809\" decoding=\"async\" src=\"https:\/\/i0.wp.com\/multahost.com\/blog\/wp-content\/uploads\/2026\/04\/VOS3000-SIP-Authentication-Retry-VOS3000-SIP-Early-Hangup-VOS3000-SIP-Session-Timer-Refresh-VOS3000-Non-Timer-Endpoint-Safety-VOS3000-SIP-NAT-Keepalive-4.png?resize=809%2C540\" alt=\"VOS3000 SIP Authentication Retry, VOS3000 SIP Early Hangup, VOS3000 SIP Session Timer Refresh, VOS3000 Non-Timer Endpoint Safety, VOS3000 SIP NAT Keepalive, VOS3000 SIP Resend Interval, VOS3000 SIP INVITE Timeout, VOS3000 SIP Call Progress Timeout, VOS3000 SIP Outbound Registration Parameters, VOS3000 SIP Privacy Header, VOS3000 SIP Routing Gateway Contact, VOS3000 SIP Publish Expire, VOS3000 SIP Display From, VOS3000 SIP Send Unregister\" title=\"\"><\/td><\/tr><\/tbody><\/table><\/figure>\n","protected":false},"excerpt":{"rendered":"<p>Master VOS3000 SIP routing gateway contact with SS_SIP_ROUTING_GATEWAY_INVITE_USE_CONTACT. Configure Contact header routing, request-line callee handling, and To field preservation for VoIP softswitch.<\/p>\n","protected":false},"author":1,"featured_media":3146,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[2,620,744,622,681,682,684],"tags":[8568,8603,8606,8600,8583,8574,8569,8596,8578,8463,8581,8591,8605,8576,8594,8588,8589,8534,8601,8586,8587,8571,8598,8585,8577,8597,8579,8595,8602,8599,8609,8570,8575,8385,8582,8573,8567,8590,8611,8584,8604,8607,8580,8379,8593,8572,8608,8592,8610],"class_list":["post-3162","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-vos3000","category-vos3000-features","category-vos3000-gateway-group","category-vos3000-gateway-management","category-vos3000-setup","category-vos3000-setup-guide","category-vos3000-sip","tag-ss_sip_routing_gateway_invite_use_contact","tag-vos3000-additional-settings-sip-parameter","tag-vos3000-call-routing-contact-header","tag-vos3000-callee-number-from-request-line","tag-vos3000-callee-number-selection","tag-vos3000-contact-header-callee","tag-vos3000-contact-header-routing","tag-vos3000-contact-header-vs-to-header","tag-vos3000-contact-port-routing","tag-vos3000-gateway-additional-settings-sip","tag-vos3000-gateway-invite-use-contact","tag-vos3000-gateway-peer-number-information","tag-vos3000-gateway-protocol-sip-configuration","tag-vos3000-invite-header-guide","tag-vos3000-invite-request-line-number","tag-vos3000-mapping-gateway-callee-field","tag-vos3000-mapping-gateway-caller-field","tag-vos3000-operation-management-sip","tag-vos3000-original-number-to-field","tag-vos3000-reply-address-socket-via","tag-vos3000-request-address-contact-port","tag-vos3000-request-line-callee-number","tag-vos3000-routing-gateway-invite-settings","tag-vos3000-routing-gateway-protocol","tag-vos3000-routing-gateway-sip-settings","tag-vos3000-sip-call-flow-contact","tag-vos3000-sip-call-routing-header","tag-vos3000-sip-callee-routing-configuration","tag-vos3000-sip-gateway-contact-port","tag-vos3000-sip-header-manipulation","tag-vos3000-sip-header-routing-best-practices","tag-vos3000-sip-invite-contact-header","tag-vos3000-sip-number-routing","tag-vos3000-sip-protocol-parameters","tag-vos3000-sip-request-line-routing","tag-vos3000-sip-routing-gateway-configuration","tag-vos3000-sip-routing-gateway-contact","tag-vos3000-sip-signal-caller-selection","tag-vos3000-sip-signaling-contact-header","tag-vos3000-sip-to-header-preservation","tag-vos3000-sip-troubleshooting-contact","tag-vos3000-sip-trunk-contact-routing","tag-vos3000-softswitch-contact-header","tag-vos3000-softswitch-management-sip","tag-vos3000-softswitch-sip-routing","tag-vos3000-to-field-handling","tag-vos3000-vendor-gateway-contact-settings","tag-vos3000-voip-contact-header","tag-vos3000-voip-softswitch-contact"],"acf":[],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"https:\/\/i0.wp.com\/multahost.com\/blog\/wp-content\/uploads\/2026\/04\/VOS3000-SIP-Call-Progress-Timeout-VOS3000-SIP-Outbound-Registration-Parameters-VOS3000-SIP-Privacy-Header-VOS3000-SIP-Routing-Gateway-Contact-VOS3000-SIP-Publish-Expire-VOS3000-SIP-Display-From.png?fit=1536%2C1024&ssl=1?v=1776736554","jetpack-related-posts":[{"id":3209,"url":"https:\/\/multahost.com\/blog\/vos3000-callee-source-header\/","url_meta":{"origin":3162,"position":0},"title":"VOS3000 Callee Source Header Flexible To Request-Line Selection Important","author":"king","date":"April 21, 2026","format":false,"excerpt":"VOS3000 callee source header selects destination number from To header or Request-Line. 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