Incoming call to FXO port drop on answer.

[Mr. John Doe]

Good day,

I having the following scheme.

CUCM<=>VG224 <=> VIC2-FXO4*2921<=>CP7911(SIP)

CUCM and VG224 are customer managed, so cannot be debugged or reconfigured.

Customer provides 6 analog lines.

The problem is that any call coming to voice-port 0/0/2 is dropped upon picking the handset.

Tried to swap 2 physical lines between each other to check if problem lays within FSX on VG224 - same result, calls to voice-port 0/0/2 are dropped on answer.

Checked FXO card on another 2811 router - all ports of the card are receiving and placing calls.

Replaced the card with the same one - again, all calls to voice-port 0/0/2 are dropped.

Meanwhile, outgoing calls through this port are working fine.

Also tried different IOS versions 155-3.M6, 155-3.M6a, 154-3.M8 and 153-3.M10

Phones are currently configured to use SIP, however rebuilding the system to SCCP didn't give any result. So, moved back to SIP as phones are living on different subnets. Also tried a Snom370 phone.

Attached are config and debugs of my 2921. Note, currently all connection plar are set to 166077 for testing.

Please help. I end up with searching where the problem is.

[Mohammed al Baqari]

In the voice ports change the signaling from loop start to ground start

[Mr. John Doe]

voice-port 0/0/2
 signal groundStart
 connection plar opx 166077

didn't work.

[Georgios Fotiadis]

I don't see any error in your configuration. Debug logs suggest a port error. I know that you have tried this card to another router and it works properly, but to be sure I would suggest these:

- swap the two FXO cards

- try use another HWIC slot on the 2921 router; i.e. move FXO card from slot 0 to slot 2 ot 3.

[Mr. John Doe]

Will check with HWIC slot change next week as currently cannot get to site.

[MOHIT SINGH]

Hi,

Please try configuring "no battery-reversal"under voice port as it can also disconnect calls. If it still fails please collect debug vpm signal and debug voip ccapi inout with the command configured.

[Mr. John Doe]

Same crap but with additions.

Drop to calling side. And calling tones from handset on my side.

[MOHIT SINGH · Accepted solution]

In the logs, I can still see battery reversal happening. Can you please try to configure "supervisory disconnect dualtone mid-call" to change the disconnect method?
https://www.cisco.com/c/en/us/support/docs/voice/analog-signaling-e-m-did-fxs-fxo/8120-fxo-disconnect.html#topic7

[Mr. John Doe]

Sorry for delay, tried as you suggested this morning and everything went fine.

voice-port 0/0/2
 supervisory disconnect dualtone mid-call
 no battery-reversal
 connection plar opx 166077

So, do I need to set it on all ports or there is some hardware problem on 2921?

[Mr. John Doe]

Some update.

Situation has not been solved, just got much better than before.

About 20-30% of calls are still dropped and this time on all ports.

[MOHIT SINGH]

Changing configuration on one port should not effect other ports. The call was disconnected from VG224 side as you can see FXO received (E_DSP_SIG) a disconnect signal. 

[0/0/2, FXOLS_CONNECT, E_DSP_SIG_1100]fxols_offhook_disc

Is it possible to get logs from VG224? Please collect logs together not separately

debug voice application stcapp

debug vpm signal

debug voip ccapi inout

[Mr. John Doe]

In general, current state of the system is acceptable as these lines are to be used over VSAT link on the vessels as a reserve for two other DID lines from another provider, therefore rare use is expected.

Thanks a lot for your help.

[Mr. John Doe]

BTW, customer has shared some conf of CUCM and VG, so may be it will be helpful.

[MOHIT SINGH]

Try to disable battery reversal on FXS port of VG224 and then check. I am not sure but may be try it.