Fax issue with VG224 after migrating H.323 gateway from 2821 to 2921

A few bright Voice guys here so maybe someone has ran into this.

H.323 gateway with PRI, upgraded from 2821 to 2921. Site uses VG224s for fax machines and various analog devices.

PVDM3s in 2900 series do not support fax relay like PVDM2s in 2800 so I had to change the configs on the router and VG224s to pass through. Unable to send outbound faxes on machines running on VG224s. Same fax machine on an ATA will work fine.

Any ideas?

2921 Config

voice service voip
allow-connections h323 to h323
allow-connections h323 to sip
allow-connections sip to h323
allow-connections sip to sip
fax protocol pass-through g711ulaw
h323
sip
bind control source-interface loopback1
bind media source-interface loopback1
!
voice class codec 1
codec preference 1 g711ulaw
codec preference 2 g729r8
!
voice class codec 2
codec preference 1 g729r8
!
voice class h323 1
h225 timeout tcp establish 3
call preserve

VG224

voice service voip
fax protocol pass-through g711ulaw

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Comments

shodown

VG224's can be kinda picky. If you are using SIP trunk you may have to switch to MGCP. Also since you are on a 2900 did you enter the voice security IP addresses that the VG traffic will be sourced from.

aaron0011

shodown wrote: »

VG224's can be kinda picky. If you are using SIP trunk you may have to switch to MGCP. Also since you are on a 2900 did you enter the voice security IP addresses that the VG traffic will be sourced from.

Site is using a PRI and I just rid our entire environment of the last few MGCP gateways so want to stick with H.323. Previous 2821 was H.323 with the same PRI.

Not familiar with voice security IP? Btw, we only have a handful of VG224s out there and this is the first one that is going through a 2900. The others are still on 2821s.

Thanks for the reply.

swild

Try removing the commands for g729 in order to force g711 across the board. Faxing requires g711.

shodown

if you are using 15x code you have to allow certain subnets to pass by using the VoIP security feature set.

Also run a debug voip ccapi inout to see why its not working. I can tell more by the disconnect code.

Also if you upgrade to SIP trunks you won't have a choice with MGCP on the VG device. SIP doesn't have all the features. On a very slow connection now, but will be full speed in 2 hours. Time is 635 EST.

Trifidw

We're going to be doing this in the new year so would be interested in finding out how you resolved it.

Do you have any ATAs to test faxing through?

aaron0011

Trifidw wrote: »

We're going to be doing this in the new year so would be interested in finding out how you resolved it.

Do you have any ATAs to test faxing through?

ATAs will work with Fax machines as long as they use G3 and not SG3 (14.4 vs 33.6 on baud rate). ATA 186 and 187 do not support SG3. We have a few credit card machines that will not work on ATAs for this reason.

aaron0011

shodown wrote: »

if you are using 15x code you have to allow certain subnets to pass by using the VoIP security feature set.

Also run a debug voip ccapi inout to see why its not working. I can tell more by the disconnect code.

Also if you upgrade to SIP trunks you won't have a choice with MGCP on the VG device. SIP doesn't have all the features. On a very slow connection now, but will be full speed in 2 hours. Time is 635 EST.

Previous config in 2821 was T.38 and didn't work on 2921. Added the following to 2921 and VG224 configs to fix the issue.

voice service pots
fax rate disable
!
voice service voip
fax protocol none
modem passthrough nse codec g711ulaw

Also, VG224 set to Fax Passthrough and Modem Passthrough Enable in CUCM.

shodown

Great job on the troubleshooting.

aaron0011

shodown wrote: »

Great job on the troubleshooting.

Thanks shodown. Pretty obscure issue so hopefully this post will help someone in the future.