SIP inbound dial peer selection

[aalejo]

Trying to explain why an inbound call matches one dial peer and not other in a customer configuration. 

I come  across a nice document on CCO https://www.cisco.com/c/en/us/support/docs/voice/ip-telephony-voice-over-ip-voip/211306-In-Depth-Explanation-of-Cisco-IOS-and-IO.html. But document does not match real life dialpeer behavior.

1. If two inbound uri dial peer, one matches by "from" and the other by "via", witch one has the preference? According to CCO document, both have same preference but according to my test, "via" has preference.

2. If two  inbound uri dial peer have exact the same priority (both matches using "from"), witch one has the preference? According to CCO document the one that has the  largest tag but on my configuration any of the two could match.

Any ideas?

[Ayodeji Okanlawon]

Hey Alex,

The first part is straight forward. The via header has preference over the from header. This is a well established fact. The document also states this is based on the order of dialpeer selection for incoming URI matching.

On the second, I can't comment but will go with your real life experience. IOS version may also play a part here...

[aalejo]

Hey Ayodeji

We are working w TAC to fix that document. 

For the first part document gave equal  preference to via, request, to and from header match. That's is being fix.

For the second part it said "In the event of a tie-breaker where multiple dial-peers have the same match length and preference the IOS assumes the inbound dial-peer with the largest number tag as the incoming dial-peer".  Also being fix and being under testing on several platform and several version and conditions.

Regards

Alex