sbc trunking · published

Troubleshooting CUBE calls that match the wrong dial-peer

Verified 2026-10-02 · 60 sources · tier 2

Each call through a Cisco IOS gateway is associated with one inbound dial peer for the incoming call leg and one outbound dial peer for the outgoing call leg, which the gateway then bridges 53. When no configured dial peer matches an inbound call, the gateway uses the default dial peer 0, which has no DTMF relay mechanism 911.

How inbound matching works

For SIP calls, the inbound dial-peer preference order is incoming uri via, incoming uri request, incoming uri to, incoming uri from, then called number, calling number, destination-pattern (ANI) and finally carrier-id 50.

All dial peers are searched on the first match criterion, and the gateway moves to the next criterion only if no match is found 21. An inbound dial peer only needs to satisfy one of its configured matching conditions, and not every attribute needs to be configured or match the call setup 38. WarmTransfer's reading of the sources is that a dial peer can win on a high-preference criterion such as a URI match before a dial peer configured with the expected called number is considered 5021.

Number-based rules

The router first tries to match the called number (DNIS) of the call setup against the incoming called-number configured on each dial peer 26. If no dial peer matches on incoming called-number, the gateway next tries to match the calling number (ANI) against the answer-address configured on dial peers 25. If neither produces a match, the gateway tries to match the calling number (ANI) against the destination-pattern configured on dial peers 27. As a later criterion, the gateway matches the dial peer port against the voice port of the incoming call 29. If several dial peers have the same port, the dial peer first added to the configuration is matched 29.

At each inbound matching step, if several dial peers match, the one with the longest explicit match is chosen 28.

Cisco recommends using incoming called-number for inbound dial-peer matching because call setups always include DNIS information 48. By default no incoming called-number is defined on a dial peer, so inbound calls are associated with that dial peer only by answer-address, destination-pattern or interface matching 37. We infer that a dial peer configured only for outbound use, whose destination-pattern matches the caller's ANI, can be selected as the inbound dial peer 2737.

URI-based rules

incoming uri via matches on the topmost Via header of the incoming SIP INVITE, which identifies the neighbouring SIP entity that forwarded the request, not the original caller 59.

If several dial peers match an incoming call on URI, the longest matching dial peer is chosen, as with called-number matching 55. A voice class uri pattern match has no match length and is therefore the least preferred URI match 56.

When matching a voice class uri, the gateway by default prefers the host portion, then the user portion, then the tel-URI, then an exact match of the full URI 57. This order can be changed with voice class uri sip preference 57.

Only 10 hosts, 1 pattern or 1 user-id can be configured per voice class uri, and regular expressions are the workaround for broader matching 54. The incoming uri command can be configured multiple times in the same dial peer with different keywords 30. The incoming uri command was introduced in IOS 12.3(4)T, and the via keyword was added in IOS 15.1(2)T 58. Calls that use an E.164 number rather than a URI use the dial-peer matching rules that existed before IOS 15.1(2)T 18.

Other factors that change inbound eligibility

From IOS 15.6(3)M and IOS XE 16.3.1, the gateway can filter eligible inbound dial peers to those matching the VRF ID of the interface the call arrived on 60.
On a router also running CUCME, CUCME system dial peers take preference over configured SIP dial peers 6.
The H.323 protocol is not supported on CUBE from Cisco IOS XE Bengaluru 17.6.1a onwards. H.323 inbound matching rules (incoming uri called or calling) therefore apply only to earlier releases 22.

Default dial peer 0

Default dial peer 0 advertises any codec and has voice activity detection (VAD) enabled 8. Because it has no DTMF relay mechanism, a call that lands on dial peer 0 cannot negotiate DTMF relay such as cisco-rtp 11.

Cisco's worked example resolves an inbound VoIP call that matches dial peer 0 by adding an incoming called-number pattern to an explicitly configured inbound VoIP dial peer, so that capabilities such as cisco-rtp DTMF relay are negotiated 10.

How outbound matching works

Cisco's call-routing technote lists the outbound dial-peer search order as dial-peer group (destination dpg), provision-policy URI, ILS route string, URI with carrier-id, called number with carrier-id, URI alone, called number (destination-pattern or e164-pattern-map), then calling number 41.

The CUBE IOS XE 17.6+ configuration guide lists outbound matching as destination route-string, destination URI with carrier-id, destination-pattern with carrier-id, destination URI, destination-pattern, then target carrier-id 5.

For outbound dial-peer matching on a DID call, the device uses the entire incoming dial string 40. For non-DID calls, outbound matching is done digit by digit 40.

The default dial-peer hunt scheme (0) selects by longest match in phone number, then explicit preference, then random selection 23. dial-peer hunt accepts values 0 to 7 23. On dial peers a lower preference value means higher priority, and the default preference is 0 47. If the first selected outbound dial peer fails, the gateway tries the next eligible dial peer unless huntstop is configured 24.

An outbound VoIP dial peer needs a valid outbound matching mechanism and a valid session target to be operationally up 39. An inbound dial peer needs only a valid inbound matching mechanism 39. A dial peer in busyout state, caused by a keepalive failure, is taken out of service and not used for routing 1.

Dial-peer groups, provision policies and pattern maps

Dial-peer groups

When an incoming call matches an inbound dial peer with an active destination dial-peer group, dial peers from that group route the call and no other outbound dial-peer selection is used 14. The group's state then determines what happens next 1612:

If a dial-peer group is shut down, regular outbound dial-peer search occurs 16.
If all dial peers in an active dial-peer group are unavailable, the call is disconnected. It does not fall back to regular dial-peer search 12.

Outbound dial peers used in a dial-peer group still require a destination-pattern command even though matching is not done on it 13. Cisco's Local Gateway guide configures destination-pattern BAD.BAD on outbound dial peers 35. The guide states that a dummy destination pattern is required when routing via an inbound dial-peer group 35.

Within a dial-peer group, if no preference is set for member dial peers, selection order is random or as set by the dial-peer hunt command 15. The dial-peer group feature works only with a valid E.164 pattern, and calls are statically routed to one of the dial peers in the active group 17.

Provision policies

The Inbound Leg Headers for Outbound Dial-Peer Matching feature can select the outbound dial peer using the inbound Via, From, To, Diversion and Referred-By SIP headers plus called number, calling number and carrier ID 44.

A voice class dial-peer provision-policy is attached to the inbound dial peer with destination provision-policy 46. Its preference command sets up to 2 matching attributes in order 46. If an incoming call matches an inbound dial peer whose provision policy has no rules, outbound dial-peer provisioning is disabled 45. The call is then disconnected with cause code unassigned number (1) 45.

E.164 pattern maps

When a dial peer has multiple patterns via an E.164 pattern map, the pattern with the longest prefix is used as the matching criterion 19. E.164 pattern maps (incoming called, incoming calling and destination e164-pattern-map) are supported only on VoIP dial peers, and duplicate patterns cannot be added to one map 20.

Local Gateway matching examples

Cisco's Local Gateway guide matches calls from Webex Calling with incoming uri request 34. That command references a voice class uri whose pattern is dtg= followed by the trunk OTG/DTG value from Control Hub 34. The same guide matches calls from the SIP PSTN provider with incoming uri via 36. That command references a voice class uri that lists the provider's IPv4 host address 36.

Diagnosing it

Cisco's call-routing troubleshooting section lists show dial-peer voice summary, debug voip ccapi inout, debug voice translation, debug dialpeer, debug voip uri and test voice translation-rule 52.

Run show dial-peer voice summary to check each dial peer's administrative and operational state, preference, session target and keepalive status 51.
Run show call active voice brief to list active calls with their associated dial peers 49.
Run show call active voice to see detailed negotiated parameters such as DTMF relay, VAD and codec 49. Use this to spot a call that negotiated no DTMF relay 4911.
Capture debug voip ccapi inout. In this output the selected inbound dial peer appears as Incoming Dial-peer=<tag> and the selected outbound dial peer as Outgoing Dial-peer=<tag> 3. Cisco recommends logging this output to a buffer rather than the console, because the output volume can severely affect gateway performance 4.
Use debug voip dialpeer to see dial-peer manager results such as Result=Success(0); Incoming Dial-peer=1 Is Matched 7. Cisco advises buffered logging for this debug because it generates a large volume of messages 7.

A dial peer can be busied out after upgrading to IOS XE 16.12.6, 17.3.5, 17.6.1 or later if it has both a session server-group and SIP options-keepalive 2. Fixes are in 16.12.8, 17.3.6, 17.6.3, 17.7.1 and 17.8.1 or later 2.

Applicability

Applies to: Cisco IOS voice gateway and Cisco Unified Border Element. Deployments: on-premises. Sources checked 2026-10-02. The CUBE configuration guide material used here covers Cisco IOS XE 17.6 onwards 5. H.323 inbound matching rules apply only to releases before Cisco IOS XE Bengaluru 17.6.1a 22. VRF-based inbound dial-peer filtering is available from IOS 15.6(3)M and IOS XE 16.3.1 60. The via keyword of incoming uri is available from IOS 15.1(2)T 58. The server-group and keepalive busyout defect affects IOS XE 16.12.6, 17.3.5, 17.6.1 or later until 16.12.8, 17.3.6, 17.6.3, 17.7.1 and 17.8.1 or later 2.

What remains uncertain

Which SIP header (Request-URI user part or To) supplies the called number for incoming called-number matching on CUBE is not covered by the sources below.
The tie-breaker when 2 SIP inbound dial peers match identically with equal preference is not covered by the sources below.
Whether a toll-fraud ip address trusted list rejects INVITEs before dial-peer matching is not covered by the sources below.
The effect of voice class tenant and bind statements on inbound dial-peer eligibility is not covered by the sources below.
Where voice translation-profile applies relative to inbound and outbound dial-peer matching is not covered by the sources below.
The current IOS XE format of the debug voip ccapi inout dial-peer lines is not covered by the sources below.
Pattern-count and file-load limits for voice class e164-pattern-map are not covered by the sources below.
The maximum number of dial peers per voice class dpg is not covered by the sources below.
How the outbound search order in Cisco's call-routing technote reconciles with the order in the CUBE IOS XE 17.6+ configuration guide is not covered by the sources below.