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Cisco Unified Communications Manager Trunks (Session Management Edition deployment guide 8.6(1))

Publisher: Cisco
URL: https://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucm/session_mgmt/deploy/8_6_1/trunks.html
Published: 2010-12-17
Updated: unknown
Accessed: 2026-09-24
HTTP status: 200
License: Cisco documentation; Cisco terms of use; no-redistribution; short excerpts and locators only

Source notes citing this source

A SIP trunk that uses a standard Unified CM Group runs its SIP daemon on up to three nodes in the cluster. in context
The 8.6 SME guide says Unified CM SIP trunks use Delayed Offer by default and recommends Delayed Offer for outbound trunk calls. in context
Where Early Offer is required, the 8.6 SME guide recommends the 'Early Offer support for voice and video calls (insert MTP if needed)' option because it needs fewer MTP resources. in context
The 8.6 SME guide notes that IP PSTN service providers typically require SIP Early Offer on trunks to them and that most support voice calls only. in context
The 8.6 SME guide recommends that each leaf cluster build route lists of multiple prioritized SIP trunks, one per group of SME nodes in each data center, with Run on all Nodes enabled and a unique incoming port on each trunk. in context
The 8.6 SME guide says SIP normalization and transparency scripts can address SIP interoperability issues with third-party systems. in context
SIP OPTIONS ping is recommended on all SIP trunks so Unified CM tracks trunk state dynamically instead of per call and on timeout. in context
The 8.6 SME guide recommends enabling Run on all Active Unified CM Nodes on all route lists. in context
With Run on all Active Unified CM Nodes enabled on a SIP trunk, the outbound trunk call leaves from the same node that received the inbound call. in context
The 8.6 SME guide calls SIP the protocol of choice for intercluster trunks because Unified CM SIP trunks offer more features than H.323 intercluster trunks. in context
On the SME cluster, the 8.6 guide recommends standard Unified CM Groups for each SIP trunk, with destination IP addresses and ports defined for every call processing node in the leaf cluster. in context
Unified CM SIP trunks support topology-aware RSVP call admission control using SIP Preconditions, and locations-based call admission control that does not know the WAN topology. in context
When several trunks run on all nodes toward the same destination, each trunk needs a unique incoming and destination port number so it can be identified. in context
With OPTIONS Ping enabled, each Unified CM node running the trunk's SIP daemon periodically pings each destination and sends calls only to reachable destinations, instead of discovering failures per call through timeouts. in context
Unified CM considers the trunk in service when at least one node gets a response other than 408 or 503 from at least one destination address. in context
With SIP OPTIONS Ping enabled, Unified CM considers a trunk destination out of service if it does not respond to OPTIONS, responds 503 or 408, or a TCP connection cannot be established. in context
Whether a 503 in reply to an OPTIONS keepalive takes a trunk down depends on the platform: Unified CM documents it as out of service, AudioCodes makes it configurable, and Teams Direct Routing health depends on whether the SBC keeps sending OPTIONS rather than on the response code. inferred in context
Unified CM treats a trunk as in service when at least one node gets a response other than 408 or 503 from at least one destination address. in context
Unified CM marks a trunk destination address out of service if it does not answer an OPTIONS request, answers with 503 Service Unavailable or 408 Request Timeout, or a TCP connection to it cannot be set up. in context
In Unified CM, SIP OPTIONS Ping is turned on in the SIP Profile attached to a SIP trunk. Every node running the trunk's SIP daemon then periodically sends OPTIONS to each of the trunk's destination IP addresses. in context
Cisco recommends enabling SIP OPTIONS Ping on all SIP trunks, because Unified CM can then track trunk state as it changes instead of discovering it per call through timeouts. in context
Reachability and readiness to take calls are different things, and platforms map them differently. RFC 3261 lets a UAS answer OPTIONS with a non-200 status to show readiness, Unified CM counts only 408, 503 or no response as out of service, and Kamailio's dispatcher by default accepts only 200 OK. The same far-end reply can therefore keep a trunk up on one platform and mark it down on another. inferred in context

Cite this source record

APA

WarmTransfer. (2010, December 17). Cisco Unified Communications Manager Trunks (Session Management Edition deployment guide 8.6(1)). WarmTransfer. https://warmtransfer.net/knowledge/sources/cisco-sme-861-trunks

BibTeX

@misc{warmtransfer-cisco-sme-861-trunks,
  title  = {Cisco Unified Communications Manager Trunks (Session Management Edition deployment guide 8.6(1))},
  author = {{WarmTransfer}},
  year   = {2010},
  url    = {https://warmtransfer.net/knowledge/sources/cisco-sme-861-trunks},
  note   = {Cisco, accessed 2026-09-24}
}