[cisco-voip] SIP Fail over

[Ryan Huff]

Couldn't you just use voice class sip options/keepalives to mark when the ITSP is down, so CUCM marks the trunk out of service and fails to the next route group member immediately (ideally, your secondary CUBE)? Seems like thats a more natural way of doing it versus using IP SLAs...

Thanks,

- Ryan
________________________________
From: cisco-voip <cisco-voip-bounces at puck.nether.net> on behalf of Erik Anderson <erik.anderson.85 at gmail.com>
Sent: Thursday, December 20, 2018 12:03 PM
To: cisco-voip voyp list
Subject: [cisco-voip] SIP Fail over

Morning Folks,


We have implemented a new SIP solution with Level 3 and found that we have outbound calling failover issues. When a CUBE loses its ability to talk to its Level 3 Peer, but can still talk to CUCM outbound calls will still connect to the CUBE, but fail connecting to Level 3. In turn CUCM still thinks the call is connected since the CUCM SIP trunk remains up to the CUBE.



Architecture Notes:



4 Locations with 1 CUBE Each

4 CUCM SIP Trunks with each connecting to one of the 4 CUBEs

4 CUCM Route Groups with Various CUBE/SIP Trunks assigned a Distribution Algorithm of Top Down

Each CUBE has 2 SIP Peers

Each CUBE can only talk to its respective SIP peer via its local Level 3 Transport to reduce call control latency by not allowing it to use the DMVPN backup network

Level 3 does not support SIP Options Ping

CUCM Trunks have SIP Options Ping enabled



Call Flows:



Working Flow:



Phone ----> SLRG ----> Route Group Member #1 ----> CUBE SIP TRUNK ----> CUBE ----> Level 3 Transport ----> Level 3 SIP Peer #1/#2 ----> Call Completes





CUBE Failure:



Phone ----> SLRG ---->

         Route Group Member #1 ----> CUBE SIP TRUNK --X--> CUBE (CUCM Cant Reach CUBE)



        CUCM Routes Call to Next Route Group Member



                              Route Group Member #2 ----> CUBE SIP TRUNK ----> CUBE ----> Level 3 Transport ----> Level 3 SIP Peer #1/#2 ----> Call Completes



Level 3 Transport Failure/SIP Server Failure:



Phone ----> SLRG ---->

         Route Group Member #1 ----> CUBE SIP TRUNK ----> CUBE --X--> Level 3 Transport (CUBE Cant Reach Level 3 SIP Server)



        CUCM Thinks Call Connects since the CUBE accepts the call, Phone gets dead air, never tries the next RG Member





My idea to fix this is to use an IPSLA to ping the pingable address on the Level 3 SIP Servers. If both address are unreachable then shutdown the CUCM Dial-Peers. This doesn’t sounds like the best way of fixing it, but it should work.



If any has any other better ideas please let me know.

--
Erik Anderson
Telecom Manager
Some Random Corp.
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