Cisco VG450 NIM-4FXO Interface Issue: Call Does Not Clear

[conor.maton]

Hello all,

I have a Cisco VG450 Voice Gateway with NIM-4FXO cards. I am interfacing to a PABX via copper and have an interface issue.

After some tweaking to sort a previous issue where an incoming call ringing cut out after less than a second (resolved by adding ‘no battery-reversal’) but now I have an issue where when the call is ended by the far end phone (e.g. mobile phone) it presents with a Number Unobtainable tone and doesn’t automatically clear on the CUCM handset (Cisco 8845)

See Cisco VG450 FXO config below (FXO port 0/3/2)

!
voice-port 0/3/2
 no battery-reversal
 cptone GB
 timing hookflash-out 50
 impedance complex2
!
dial-peer voice 999032 pots
service mgcpapp
port 0/3/2
!

I know there are many tweaks that can be made on the Cisco VG450 FXO port but wondered if there is another command that will resolve this please?

I have attached the FXO debug and MGCP debug during two separate calls to see what is happening. I’ve also attached the NU tone recorded from the CUCM phone when ended on the receiving mobile phone

Any help would be greatly appreciated!

[conor.maton]

Anyone with any ideas please?

I found the below fourm thread, is this worth investigating or is this a different issue altogether?

https://community.cisco.com/t5/ip-telephony-and-phones/fxo-disconnect-problem-again/td-p/1700180

[Elliot Dierksen]

What is the PABX to which the VG450 is connected? Is it possible to use ground start instead of loop start (the default). Loop start is notorious for not detecting remote party disconnects in exactly the way you describe. Is FXO your only choice? If you have have multiple ports then a T1/E1 PRI would be a way better option.

[conor.maton]

Hi

The PABX is a Mitel MXOne

I could try ground start instead of loop start and see what happens. I don't have any control of the MXOne so I need to make the necessary tweaks on the VG450 to get it working which means using an FXO port

[Elliot Dierksen]

You would have to work with someone who has the ability to change that setting on the Mitel side (assuming the line card is ground start capable). That is the only really solid solution I can suggest while using an older (and at this point in time quite undesirable) connection like an FXO line. I rarely see analog ports these days, but you the 'no battery-reversal' could also be aggravating this. Loop start connections have some serious limitations inherent in them.