Intermittent problems with faxing using VG224 gateway

Unanswered Question
Jul 29th, 2008

I recently installed a vg224 for fax capability and setup using sccp. I am running CUCM 6.1.1. All faxes connected to this device have dial tone and can dial out and receive calls but faxes do not always work. About 80% of the time faxes get a comm error after they have connected. Then on redial it works, sometimes. The same goes for receiving faxes. This is very frustrating, please help. See attached config for the vg224.



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Justin Brenton Tue, 07/29/2008 - 13:25

Hi zzbronski,


The link below will definately help you out.


This command in particular will help if you have packet loss or jitter. Also you may want to hardcode your fax rate in your configuration.


8. Disable Fax Relay ECM (Cisco Proprietary VoIP Only)


For networks with packet loss and lots of jitter, disable ECM to improve fax relay calls. Issue the command fax-relay ECM disable (discussed in more detail in the Configuration section of this document) to turn off ECM so that a larger amount of jitter and packet loss can be tolerated.


Issue the fax-relay ECM disable command to improve fax relay performance in lossy networks, but this command is also recommended for basic troubleshooting. Even if there is not a noticeable jitter problem in the network, this command can sometimes help determine fax relay problems. This command is available under VoFR and VoATM dial-peers but currently works only for VoIP.


Note: This command also activates the packet loss concealment feature.


fax-relay ECM disable Command


vnt-3660-23(config-dial-peer)#dial-peer voice 3

vnt-3660-23(config-dial-peer)#fax-relay ECM disable



http://www.cisco.com/en/US/customer/tech/tk652/tk777/technologies_tech_note09186a0080114565.shtml



Hope this helps, please rate if so.


Regards,

Justin

zzbronski Wed, 07/30/2008 - 04:30

I am unable to enter this command because it is not a valid command. see error below:


flmai002-t03(config-dial-peer)#fax-relay ECM disable

^

% Invalid input detected at '^' marker.


Michael Hanes Thu, 07/31/2008 - 19:03

Because you have the VG224 configured for SCCP, all of the fax configuration takes place globally under "voice service voip". I believe that the default fax transport method for SCCP in your version of IOS is Cisco fax relay. The first question is - what is the fax transport method that you have configured on your other voice gateways that this VG224 must talk to in order to complete fax calls? Are you using Cisco fax relay on the other voice gateways in your network? If so, do some of these gateways fail more than others when handling fax calls with this VG224?


You should be aware that these sorts of problems can be painful to track down. If possible find a reproduceable failure and then post the config of the other voice gateway that is participating in this fax call with the VG224.


Regards,

David

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