Problems with FAX in a VoIP environment

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May 4th, 2009
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We have the following scheme:

PRI---GWoutside(FAX1 with FXS)---SW3750--(fiber)---SW3750---GWinside-(FXS)-FAX2

The FAX1 can send and receive fax to/from PSTN perfectly, but FAX2 fails randomly, so I think the problem is in IP path. It usually can send fax to PSTN, but the reception fails very often. I have seen show voice call summary, and it negotiates codec g729r8. After a while it change the codec to cisco (it uses cisco fax relay by default). When the reception fails I can't see cisco codec because it disconnects before that. What is the best way to do this implementation? I think the CCM is not necessary involucred.

Best regards.

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Nicholas Matthews Mon, 05/04/2009 - 11:16
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If you suspect packet loss, use 'show call active voice brief' or 'show call history voice brief' to check for packet loss. loss:x/x/x



victorgarciaternero Tue, 05/05/2009 - 01:35
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Hello Nick, thank for your response. I think there is no packet loss:


Any other idea?

Best regars


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