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  • Faxing on 8.1 and possible work-around


    I have been battling an issue recently that I wanted to post about. Basically I have 9 sites and a few of them have recently been experiencing issues with fax reliability. Long story short, inbound and outbound faxes would fail on a regular basis.

    I tried everything in relation to codecs, I made test calls with all of the various codecs with mixed results. Eventually I tried creating a new user group and restricting the group to the local PSTN network connection (T1, POTS, etc...), and this seems to have made a huge difference. I believe that when the calls were traversing the WAN they were defaulting to the intrasite codec (G729 in this case) and they were failing. By restricting them to the local circuit, they could use a higher bandwidth codec.

    For those of you that have been fighting the same issue you may want to give this a shot.

  • #2
    Faxing across the WAN in not a good idea unless you're using ST 10 which introduces T.38 for faxing.

    Edit: I should also add that T.38 is only supported on the half width switch.
    Last edited by Dr_Klahn; 02-01-2010, 11:16 AM.


    • #3
      It sounds more like network issues to me. Do you have QoS on your WAN? Are you seeing 119 errors in your logs? I am guessing you'll see a lot of them. The fax calls should default to the fax codec. You will probably want to check your switches, routers, etc, for errors, packet loss and the like.

      That using POTS works says to me that your system is functional, the problem is most likely sending packets across the WAN. You can also try sending a fax between site A and B and try WAN vs POTS and see what works and what doesn't. My guess would be either switch problems (duplex mismatches? bad cables? hubs instead of switches?), or WAN/QoS issues (dirty T1s, lack of prioritization, overutilization etc)


      • #4
        Yeah we use QoS and are on an MPLS network. Each site has plenty of bandwidth to handle the calls as well as a reservation for up to 3/4 of site bandwidth. The idea of allowing cross-site faxing was to take advantage of least cost routing but sometimes it's better to just pay for the LD than to deal with quality and reliability issues. By default unless you specifically restrict the fax machines to the local trunks through a user group they will try to send via a local trunk if it is available. My point in my initial post was that others experiencing this issue might want to verify their configs to make sure that the user group assigned to the fax machine has the correct permissions.