ISR4k SIP SRST with SIP PSTN

[miket]

I am running SRST on an ISR 4431 on latest IOS. When I was in sRST mode the phones were able to dial each other with no issues but when I tried dialing out to the PSTN all calls failed after 4 digits. I am using all SIP phones and have SIP to the PSTN.

I see this in the debug. Why would transcoder cause failure. I am using G.711 everywhere.  Anyone seen this behaviour

Call-ID: 701f534d-7f9d00d6-0d021f45-33936e63@X.X.X.X
CSeq: 101 INVITE
Allow-Events: telephone-event
Warning: 399 X.X.X.X "Transcoder Not Configured"
Server: Cisco-SIPGateway/IOS-16.9.5
Reason: Q.850;cause=47

[Ayodeji Okanlawon]

Hi,

To get better help do endeavor to provide full details of logs. Unless we are magicians we can't accurately tell you what the issue is without enough information... Having said that have you considered what codecs are advertised by the phones when the call us made and then compare that to the codec configured on the dial peer to your ITSP? 

[TONY SMITH]

I suggest also tweaking the SIP timers and retries.  I usually set these something like this.  The default of 500 ms and 6 retries means around a 30 second delay before it gives up.

sip-ua
 retry invite 2
 timers trying 350

Setting these to comfortable values means you won't get unacceptable delays on your outbound calls if the preferred link fails, until the option polling times out and shuts down the dial peer.