# Trunks route groups and dial plans in Control Hub Canonical: https://warmtransfer.net/knowledge/webex-calling-trunks-route-groups Last verified: 2026-09-16 A trunk in Webex Calling provides a connection between Webex Calling and the premises, terminated on the premises by a supported session border controller acting as a Local Gateway[^8]. A route group groups these trunks to distribute calls across them or provide redundancy, and it may include trunks from multiple locations[^7]. ## Trunks and Local Gateways A Webex Calling trunk name cannot exceed 24 characters[^25]. A Webex Calling location may hold a maximum of 100 trunks[^3]. For certificate-based trunks, the fully qualified domain name (FQDN) or SRV host address must be unique across the entire organization, and using a different port does not create a unique address: a trunk at `london.lgw.cisco.com:5062` cannot be created if another trunk uses the host address `london.lgw.cisco.com` in either FQDN or SRV form[^10]. The trunk address must resolve from the public internet using a DNS A record or a DNS SRV record[^11]. An FQDN must resolve to an A record rather than a CNAME, an SRV service type must use the prefix `_sips._tcp`, and Cisco prefers a time to live of 300 seconds or higher across all record types[^11]. If an SRV address is used, both the SRV record and its derived A record must be listed in the subject alternative name (SAN) of the Local Gateway certificate, and the certificate's common name or SAN must contain the FQDN selected for the trunk in Control Hub[^24]. A trunk's SRV address, FQDN, or port cannot be edited once created[^12]. Modifying any of these values requires creating a new trunk and deleting the existing one, and a trunk can be deleted only when it is not in use[^12]. A trunk reports 1 of 4 operational statuses, refreshing every 3 minutes: Online indicates that every Webex Calling edge proxy connected, Offline indicates that none connected, Impaired indicates that at least 1 edge proxy did not connect, and Unknown indicates that a connection is in progress for a recently added Local Gateway[^27]. If a trunk search returns more than 1000 trunks, the interface stops sorting the results and disables searching within them[^26]. The trunk troubleshooting table lists 17 numbered error conditions, and Cisco states that 4 of these—numbers 2, 6, 11, and 12—appear only when all edge proxy nodes experience an issue[^22]. ### Header and Identity Handling The Dual Identity Support trunk setting controls whether Webex Calling can send different values in the From and P-Asserted-Identity headers on an initial outbound INVITE, setting P-Asserted-Identity identical to From when disabled[^17]. Across Cisco's 3 worked Dual Identity Support scenarios, disabling the setting alters the P-Asserted-Identity header in 2 scenarios and leaves it unchanged in the third: * A user presenting the location main number changes from a direct line to the location number in P-Asserted-Identity[^18]. * A call to an on-premises user changes from a direct line to the enterprise significant number[^18]. * A user presenting their own direct line is unaffected because both headers already contain that number[^18]. The P-Charge-Info Support policy defaults to Disabled[^19]. When enabled, it includes a chargeable number in a P-Charge-Info header on outbound PSTN calls using 1 of 2 policies: the Webex Calling primary or location main number, or a custom charge number defined on the location page[^19]. Cisco states that the P-Charge-Info header cannot be sent when no regular non-toll-free number is available, meaning the header may be omitted even if support is enabled, and that PSTN providers cannot rely entirely on P-Charge-Info and must continue to evaluate the P-Asserted-Identity or Diversion header[^20]. ## Route Groups and Rerouting A maximum of 10000 route groups can be configured for 1 enterprise customer, and each route group can hold up to 10 trunks[^5][^2]. Within a route group, calls distribute randomly among all trunks assigned to the highest priority level, and lower priority levels are reached only when every trunk at the higher priority is unavailable[^21]. Rerouting to an alternate trunk occurs under specific SIP responses and conditions[^6]: * SIP responses 401, 470, 480, and 606 when they are not preceded by a provisional 18x response[^6]. * Any other 4xx response, excluding 403, 404, 410, 413, 484, and 486[^6]. * All 5xx responses[^6]. * A 12 second SIP timeout[^6]. ## Dial Plans and Call Routing Webex Calling dial plans apply globally across an enterprise to all users regardless of location, and each dial plan directs calls to exactly 1 routing choice: either a single trunk or a route group[^16]. A customer may configure up to 10000 dial plans, and each dial plan can contain up to 10000 dial patterns[^4]. A single CSV upload can populate up to 10000 dial patterns at once[^13]. Cisco states that From and To headers within a dial plan must both be in E.164 form or both in extension form, and cannot be mixed[^15]. Numeric dial patterns support 2 wildcards[^14]: * `!` matches any sequence of digits, but it can appear only once, only at the end of a pattern, only in an E.164 pattern, and never in a pattern that also contains `X`[^14]. * `X` matches a single digit from 0 to 9, but it cannot appear in the middle of a number[^14]. SIP URI dial patterns match only the host portion located to the right of the `@` symbol[^23]. A SIP URI pattern with a leading asterisk matches sub-domains of the specified domain, but does not match the domain itself[^23]. ### Premises and Extension Routing For routing calls between Webex Calling and on-premises systems when numbers are unknown, Control Hub provides 2 options: Standard Behavior and Legacy Behavior[^29]. Cisco identifies Standard Behavior as the default and recommended choice for PBX interoperability, whereas Legacy Behavior provides backward compatibility with older local gateway behaviour and is not recommended by Cisco when dial plans are configured[^29]. The Calls to On-Premises Extensions setting is configured per location to route calls to unknown extensions of 2 to 10 digits to a designated trunk or route group as a premises call[^28]. An extension is treated as unknown when the caller identity matches no dial plan pattern, and the maximum length for unknown extensions can be configured within the 2 to 10 digit range[^28]. Control Hub includes a Verify Call Routing tool that simulates a call placed from a selected cloud user, workspace, virtual line, or premises trunk to a destination number or URI[^30]. It reports the routing decision along with evaluated outgoing call permissions, fraud prevention settings, digit patterns, call intercept configurations, and applied translation patterns[^30]. ## See also See also [Webex Calling architecture and deployment models](https://warmtransfer.net/knowledge/webex-calling-architecture). See also [Enterprise dial plan design and normalization](https://warmtransfer.net/knowledge/dial-plan-design). See also [SIP response codes and failure interpretation](https://warmtransfer.net/knowledge/sip-response-codes). See also [Webex Calling call quality troubleshooting in Control Hub](https://warmtransfer.net/knowledge/webex-calling-troubleshooting). See also [Local Gateway design and configuration](https://warmtransfer.net/knowledge/webex-calling-local-gateway). See also [Cisco Unified Border Element configuration and licensing](https://warmtransfer.net/knowledge/cube-configuration). See also [Remote site survivability patterns](https://warmtransfer.net/knowledge/survivability-remote-site). See also [Session border controller selection and certification](https://warmtransfer.net/knowledge/sbc-selection). See also [SIP trunk capacity and concurrent call planning](https://warmtransfer.net/knowledge/sip-trunk-capacity-planning). See also [Unified CM SIP trunk to CUBE configuration](https://warmtransfer.net/knowledge/cucm-config-sip-trunk-to-cube). ## Applicability Applies to: Cisco Webex Calling. Deployments: multi-tenant. Sources checked 2026-09-15. ## What remains uncertain The Webex Calling port reference guide that trunk requirements defer to is not covered by the sources below. The list of root certificate authorities accepted by Webex Calling for a Local Gateway certificate is not covered by the sources below. The specific operational differences between Legacy Behavior and Standard Behavior for unknown numbers are not covered by the sources below. The exact report output and presentation format produced by the Verify Call Routing tool are not covered by the sources below. Whether a Webex Calling dial pattern can contain a literal zero is not covered by the sources below. ## Sources [^1]: The local gateway configuration of an organisation is retrieved and modified through the Call Routing APIs, which Cisco describes as configuring dial plans, trunks and route groups, and which are the endpoints that manage routing between Webex Calling hosted users and on-premises private branch exchange users. Source: [Webex for Developers — Webex Calling Provisioning APIs](https://developer.webex.com/calling/docs/api/guides/webex-calling-provisioning-apis), Provisioning APIs guide, Local Gateway APIs section. Checked 2026-09-16. [^2]: A route group may contain a maximum of 10 trunks. Source: [Configure trunks, route groups, and dial plans for Webex Calling](https://help.webex.com/article/n0xb944/Configure-Trunks-Route-Groups-and-Dial-Plans-for-Cisco-Webex-Calling), Configurable limitations table. Checked 2026-09-04. [^3]: A Webex Calling location may hold a maximum of 100 trunks. Source: [Configure trunks, route groups, and dial plans for Webex Calling](https://help.webex.com/article/n0xb944/Configure-Trunks-Route-Groups-and-Dial-Plans-for-Cisco-Webex-Calling), Configurable limitations table. Checked 2026-09-04. [^4]: A maximum of 10000 dial plans may be configured per customer, and each dial plan may hold up to 10000 dial patterns. Source: [Cisco Preferred Architecture for Webex Calling — Design Overview](https://www.cisco.com/c/dam/en/us/td/docs/solutions/CVD/Collaboration/hybrid/AltDesigns/PA-WbxCall.pdf), Dial Plans, page 30. Checked 2026-09-04. [^5]: A maximum of 10000 route groups may be configured for 1 enterprise customer. Source: [Configure trunks, route groups, and dial plans for Webex Calling](https://help.webex.com/article/n0xb944/Configure-Trunks-Route-Groups-and-Dial-Plans-for-Cisco-Webex-Calling), Configurable limitations table. Checked 2026-09-04. [^6]: Rerouting to another trunk is triggered by SIP responses 401, 470, 480 and 606 when no provisional 18x response preceded them, by all other 4xx responses except 403, 404, 410, 413, 484 and 486, by all 5xx responses, and by a 12 second SIP timeout. Source: [Cisco Preferred Architecture for Webex Calling — Design Overview](https://www.cisco.com/c/dam/en/us/td/docs/solutions/CVD/Collaboration/hybrid/AltDesigns/PA-WbxCall.pdf), Trunks and Route Groups, page 21. Checked 2026-09-04. [^7]: A route group is a group of trunks that lets Webex Calling distribute calls over multiple trunks or provide redundancy, and it may contain trunks from multiple locations. Source: [Configure trunks, route groups, and dial plans for Webex Calling](https://help.webex.com/article/n0xb944/Configure-Trunks-Route-Groups-and-Dial-Plans-for-Cisco-Webex-Calling), Route group / Add a route group. Checked 2026-09-04. [^8]: A trunk in Webex Calling is a connection between Webex Calling and the premises, terminated on the premises by a supported session border controller acting as a Local Gateway. Source: [Configure trunks, route groups, and dial plans for Webex Calling](https://help.webex.com/article/n0xb944/Configure-Trunks-Route-Groups-and-Dial-Plans-for-Cisco-Webex-Calling), Trunk. Checked 2026-09-04. [^9]: A location using premises-based PSTN can select only 1 trunk, and the same trunk can be selected by more than 1 location. Source: [Configure Webex Calling for your organization](https://help.webex.com/en-us/article/njvdjf2/Configure-Webex-Calling-for-your-organization), Create a trunk, Before you begin. Checked 2026-09-15. [^10]: A certificate-based trunk's fully qualified domain name or SRV host address must be unique across the whole organisation, and a different port does not make an address unique: a trunk at london.lgw.cisco.com:5062 cannot be created while any other trunk uses the host address london.lgw.cisco.com, in either FQDN or SRV form. Source: [Configure trunks, route groups, and dial plans for Webex Calling](https://help.webex.com/article/n0xb944/Configure-Trunks-Route-Groups-and-Dial-Plans-for-Cisco-Webex-Calling), Add a certificate-based trunk to a location, Before you begin, Unique address across the organization. Checked 2026-09-15. [^11]: A certificate-based trunk address must resolve from the public internet through a DNS A record or a DNS SRV record; an FQDN must resolve to an A record and not to a CNAME, an SRV service type must carry the prefix _sips._tcp, and Cisco prefers a time to live of 300 seconds or higher on all record types. Source: [Configure trunks, route groups, and dial plans for Webex Calling](https://help.webex.com/article/n0xb944/Configure-Trunks-Route-Groups-and-Dial-Plans-for-Cisco-Webex-Calling), Add a certificate-based trunk to a location, Before you begin, DNS configuration. Checked 2026-09-15. [^12]: A trunk's SRV address, fully qualified domain name or port cannot be edited; changing any of them requires adding a new trunk and deleting the old one, and a trunk can only be deleted while it is not in use. Source: [Configure trunks, route groups, and dial plans for Webex Calling](https://help.webex.com/article/n0xb944/Configure-Trunks-Route-Groups-and-Dial-Plans-for-Cisco-Webex-Calling), Modify a trunk step 5, and Delete a trunk. Checked 2026-09-15. [^13]: A single CSV upload can carry a maximum of 10000 dial patterns into a Webex Calling dial plan. Source: [Configure trunks, route groups, and dial plans for Webex Calling](https://help.webex.com/article/n0xb944/Configure-Trunks-Route-Groups-and-Dial-Plans-for-Cisco-Webex-Calling), Configurable limitations table, first row. Checked 2026-09-15. [^14]: A Webex Calling dial pattern uses 2 wildcards: an exclamation mark matches any sequence of digits and may appear only once, only at the end and only in an E.164 pattern, and an X matches a single digit from 0 to 9; an X may not appear in the middle of a number and the exclamation mark may not be used in a pattern that also uses X. Source: [Configure trunks, route groups, and dial plans for Webex Calling](https://help.webex.com/article/n0xb944/Configure-Trunks-Route-Groups-and-Dial-Plans-for-Cisco-Webex-Calling), Dial plan overview, Numeric Dial Patterns and Enterprise Dial Pattern. Checked 2026-09-15. [^15]: Cisco states that a Webex Calling dial plan accepts the From and To headers in E.164 form or in extension form and that the pair cannot be a combination of the two. Source: [Configure trunks, route groups, and dial plans for Webex Calling](https://help.webex.com/article/n0xb944/Configure-Trunks-Route-Groups-and-Dial-Plans-for-Cisco-Webex-Calling), Dial plan overview, Enterprise Dial Plan Examples, note following the example table. Checked 2026-09-15. [^16]: Webex Calling dial plans are configured globally for an enterprise and apply to all users regardless of location, and a dial plan names exactly 1 routing choice, either a trunk or a route group, for the patterns it holds. Source: [Configure trunks, route groups, and dial plans for Webex Calling](https://help.webex.com/article/n0xb944/Configure-Trunks-Route-Groups-and-Dial-Plans-for-Cisco-Webex-Calling), Dial plan overview, first paragraph. Checked 2026-09-15. [^17]: The Dual Identity Support setting on a trunk decides whether Webex Calling may populate different values in the From and P-Asserted-Identity headers of an initial outbound INVITE; with it disabled, P-Asserted-Identity is set identical to From. Source: [Configure trunks, route groups, and dial plans for Webex Calling](https://help.webex.com/article/n0xb944/Configure-Trunks-Route-Groups-and-Dial-Plans-for-Cisco-Webex-Calling), Add a registration-based trunk to a location, step 5. Checked 2026-09-15. [^18]: In Cisco's 3 worked Dual Identity Support scenarios, disabling the setting changes the P-Asserted-Identity header in 2 of them and changes nothing in the third: a user presenting the location main number moves from a direct line to the location number in P-Asserted-Identity, a call to an on-premises user moves from a direct line to the enterprise significant number, and a user presenting their own number is unaffected because both headers already carry the direct line. Source: [Configure trunks, route groups, and dial plans for Webex Calling](https://help.webex.com/article/n0xb944/Configure-Trunks-Route-Groups-and-Dial-Plans-for-Cisco-Webex-Calling), Add a registration-based trunk to a location, step 5, Scenario 1 through Scenario 3. Checked 2026-09-15. [^19]: The P-Charge-Info Support policy on a trunk is set to Disabled by default, and when enabled it carries a chargeable number in a P-Charge-Info header on outbound PSTN calls under 1 of 2 policies, the Webex Calling primary or location main number, or a charge number customised on the location page. Source: [Configure trunks, route groups, and dial plans for Webex Calling](https://help.webex.com/article/n0xb944/Configure-Trunks-Route-Groups-and-Dial-Plans-for-Cisco-Webex-Calling), Add a trunk for your location, step 7. Checked 2026-09-15. [^20]: Cisco states that the P-Charge-Info header cannot be included when no regular non-toll-free number is available, so the header may be absent even when support is enabled, and that PSTN providers cannot rely solely on it and must still consider the P-Asserted-Identity or Diversion header. Source: [Configure trunks, route groups, and dial plans for Webex Calling](https://help.webex.com/article/n0xb944/Configure-Trunks-Route-Groups-and-Dial-Plans-for-Cisco-Webex-Calling), Add a trunk for your location, step 7, Limitations list. Checked 2026-09-15. [^21]: Within a route group, calls are distributed at random among the trunks that share the highest priority level, and a lower priority is used only when every trunk at the higher priority is unavailable. Source: [Configure trunks, route groups, and dial plans for Webex Calling](https://help.webex.com/article/n0xb944/Configure-Trunks-Route-Groups-and-Dial-Plans-for-Cisco-Webex-Calling), Add a route group for your location, Before you begin, worked example. Checked 2026-09-15. [^22]: The trunk troubleshooting table publishes 17 numbered error conditions, and Cisco states that 4 of them, numbers 2, 6, 11 and 12, are shown only when all the edge proxy nodes experience an issue. Source: [Configure trunks, route groups, and dial plans for Webex Calling](https://help.webex.com/article/n0xb944/Configure-Trunks-Route-Groups-and-Dial-Plans-for-Cisco-Webex-Calling), Troubleshooting table, rows 1 to 17 and the note beneath it. Checked 2026-09-15. [^23]: A SIP URI dial pattern matches only the host portion to the right of the at sign, and a pattern with a leading asterisk matches sub-domains of the named domain but does not match the domain itself. Source: [Configure trunks, route groups, and dial plans for Webex Calling](https://help.webex.com/article/n0xb944/Configure-Trunks-Route-Groups-and-Dial-Plans-for-Cisco-Webex-Calling), SIP URI Dial Pattern, syntax example table. Checked 2026-09-15. [^24]: Where a certificate-based trunk uses an SRV address, both the SRV record and the A record it derives must appear in the subject alternative name of the Local Gateway certificate, and the certificate's common name or subject alternative name must carry the fully qualified domain name chosen for the trunk in Control Hub (disputed). Source: [Configure trunks, route groups, and dial plans for Webex Calling](https://help.webex.com/article/n0xb944/Configure-Trunks-Route-Groups-and-Dial-Plans-for-Cisco-Webex-Calling), Add a certificate-based trunk to a location, note following the record-type example table. Checked 2026-09-15. [^25]: A Webex Calling trunk name cannot be longer than 24 characters. Source: [Configure trunks, route groups, and dial plans for Webex Calling](https://help.webex.com/article/n0xb944/Configure-Trunks-Route-Groups-and-Dial-Plans-for-Cisco-Webex-Calling), Add a trunk for your location, step 4. Checked 2026-09-15. [^26]: If a trunk search returns more than 1000 trunks, the results cannot be sorted and cannot be searched within. Source: [Configure trunks, route groups, and dial plans for Webex Calling](https://help.webex.com/article/n0xb944/Configure-Trunks-Route-Groups-and-Dial-Plans-for-Cisco-Webex-Calling), Trunk status, step 5. Checked 2026-09-15. [^27]: A Webex Calling trunk reports 1 of 4 statuses, where Online means every Webex Calling edge proxy connected, Offline means none did, Impaired means at least 1 edge proxy did not, and Unknown means a connection is in progress for a recently added Local Gateway; the status refreshes every 3 minutes. Source: [Configure trunks, route groups, and dial plans for Webex Calling](https://help.webex.com/article/n0xb944/Configure-Trunks-Route-Groups-and-Dial-Plans-for-Cisco-Webex-Calling), Trunk status, filter table and the note beneath it. Checked 2026-09-15. [^28]: The Calls to On-Premises Extensions setting is enabled per location and routes a call to an unknown extension of 2 to 10 digits to a selected trunk or route group as a premises call, where a caller identity that matches no dial plan pattern is what makes an extension unknown; the maximum unknown extension length is configurable over the same 2 to 10 digit range. Source: [Configure trunks, route groups, and dial plans for Webex Calling](https://help.webex.com/article/n0xb944/Configure-Trunks-Route-Groups-and-Dial-Plans-for-Cisco-Webex-Calling), Configure calls to on-premises extensions, Before you begin; and Configure call routing between Webex Calling and premises, step 5. Checked 2026-09-15. [^29]: Call routing between Webex Calling and premises offers 2 settings for unknown numbers: Standard Behavior, which Cisco gives as the default and the recommended option for interoperability with an on-premises PBX, and Legacy Behavior, which provides backward compatibility with the older local gateway behaviour and which Cisco does not recommend when dial plans are configured. Source: [Configure trunks, route groups, and dial plans for Webex Calling](https://help.webex.com/article/n0xb944/Configure-Trunks-Route-Groups-and-Dial-Plans-for-Cisco-Webex-Calling), Configure call routing between Webex Calling and premises, step 3. Checked 2026-09-15. [^30]: Control Hub publishes a Verify Call Routing tool that simulates a call from a chosen cloud user, workspace, virtual line or premises trunk to a number or URI and reports the routing decision, including the outgoing call permissions, fraud prevention, digit patterns, call intercept and translation patterns applied. Source: [Configure trunks, route groups, and dial plans for Webex Calling](https://help.webex.com/article/n0xb944/Configure-Trunks-Route-Groups-and-Dial-Plans-for-Cisco-Webex-Calling), Verify call routing, feature list and steps 4 to 6. Checked 2026-09-15.