[cisco-voip] SIP Fail over

[Kent Roberts]

Might try the option pings anyway on the cube, the cube might still honor the response as the end point is up.

   

> On Dec 20, 2018, at 10:03 AM, Erik Anderson <erik.anderson.85 at gmail.com> wrote:
> 
> 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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