Faxing with VG248 and CM 4.1.3

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Aug 18th, 2010
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Hello we have a CM 4.1.3 cluster and a VG248. For years we have had

a horrible time with faxes. Just recently we have a new need for successfuly faxing. We have about 30 fax machines hanging off the VG248.

Problem is half the time faxes go thru, other half we get random fails, redials, and some times it will even say successful but never appear on the other side.

NOTE alot of our faxing is internal, i.e. dialing internal extensions on the fax machine.

What can I do to help fix this problem? I recently updated VG248 code to latest version but it did not help.


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Christopher Graham Wed, 08/18/2010 - 20:09
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Take a look at the following document for configuring fax-passthrough on the vg:


When you fax internally, is it between two machines tied to the same VG248?  You need to make sure that the same fax transport method is configured on the originating and terminating sides.  This also holds true for faxing out to the pstn.  You will need to make sure that the same fax transport method is configured on the PSTN gateway as well as the VG.

For kicks, also make sure your regions between fax machines are configured for G711.

Hope this helps.

William Reed Wed, 08/18/2010 - 20:13
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Yes when I fax internally it is between the same VG248. I only have 1 in the enviroment.

How do I verify it is the same transport on each side? My VG248 is set for G711 U Law on Fax Passthru.

William Reed Wed, 08/18/2010 - 20:23
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If the VG is using fax passthru and it attempts to go to the PSTN in which that router is configured to use faxpassthru, will it attempt to convert the fax to fax relay transport?

Christopher Graham Thu, 08/19/2010 - 06:21
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  • Cisco Employee,

Please see the document that I provided earlier.  You need to make sure that fax configuration on EACH PORT is the same as any other fax machine you are faxing to.  The document explains how to do this.

If you are faxing to the PSTN, and both the gateway and VG are configured for fax-passthrough, then that is what should be negotiated.

William Reed Thu, 08/19/2010 - 06:29
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I did read the article and made the necessary changes to EACH PORT on my VG248.

Next step I am going to do it turn off ECM and force each fax machine to 14.4k.

Any other thoughts?

mrmhar1408 Sun, 08/22/2010 - 05:10
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upgrade the IOS image for the VG to the latest one


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