The Cisco configuration is the same when you connect to an Asterisk PBX. http://www.uccollabing.com/2014/05/16/cucm-asterisk-trunk-integration/ - Cisco CUCM does not like multiple “extensions” to REGISTER the same contact address (IP:port)
- For multiple extensions (numbers) at the same transport destination Cisco CUCM prefers to configure a “trunk” down to N720/N510
Trunk means in this case:- CUCM learns the transport destination of such “trunked” extensions (numbers) just by a local configuration inside CUCM
- CUCM does not need and does not like to receive REGISTER requests from such “trunked” extensions
We have trick available in N510/N720 to achieve such behavior: “localhost REGISTRAR simulation”
Field name | example for CUCM trunk | comment |
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Domain | <domain name or IP-address of the CUCM SIP service> | this is host part that our device uses to build an Address of Record (SIP-UIR) for this domain | SIP server (proxy) | <FQDN or IP-address of the CUCM SIP service> | - all outgoing requests except INVITE will be send to this destination - all incoming request are expected from this destination | SIP registrar | localhost | - all REGISTER requests will not leave the device but will be sent to the device it self | outbound proxy | localhost | - incoming REGISTER requests will automatically be replied internally with 200 OK
| outbound proxy mode | never | - do not use the outbound proxy field as transport destination for all SIP requests |
This way all REGISTER requests stay internal of N510/N720 and are internally confirmed with 200 OK. The MMI is happy about being successfully registered. Any initial outgoing request (e.g. INVITE) are sent to the configured “SIP server” , e.g. the CUCM. With the record-route header the CUCM can install any other proxy in the route set. As we have used the outbound proxy server field to indicate activation of a local registrar simulation, we don’t have it available to configure any other outbound proxy overruling the “recorded” routes of the CUCM network. If N510/N720 and CUCM are in different subnets, N510/N720 would usually send UDP packet { CRLF, CRLF }. To disable that you can set NAT refresh time to 0. If you need periodical SIP traffic to use the SIP trunk, you could consider to use one account in the regular manner to register an extension at the CUCM but all the other accounts to do registration just with the “localhost REGISTRAR simulation” mentioned above. |