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Problem with fax with SIP configuration


I have problem with fax configuration usig SIP trunk connection. I'll explani step by step my problem below.

I have CCM 8.6 with gateways C3925 (SIP is terminated there also have analog ports for fax) and VG224 (for analog fax machines).

At first I have ISDN PRA/PRI connection and all configuration was ok. I was able to make and recieve calls and also send and receive fax messages.

We decided to move from ISND to SIP trunk connections.

Configuration was made and now I'm able to make and receive calls but there is a problem with fax messages.

When I configured fax with T38 I wasn't able to send or recieve fax. I changed fax config to pass-through g711 and now I'm able to receive fax but i can;t send any fax. When I'm sending fax I receive error that fax wasn't.

I changed configuration for testing on analog ports on C3925 (with dial peers) so fax machines are registering directly on SIP server and in this case everything is working fine. I'm able to send and recieve fax using T38 and pass-through but now I can't do any calls on internal numbers or forward any calls to internal network - fax are only working as outside machines.

Can someone please help me or point what to change in configuration to make this fax connections work. Fax machines must be able to make calls to internal phone numbers so configuration where fax is registering directly on SIP server is not good.

Let me know if you need any debug, config or other things - I'll provide this as soon as possible.

Everyone's tags (3)
VIP Super Bronze

Problem with fax with SIP configuration

Hi Wojciech

I have looked at your configurations and I can see a few things not properly configured.

1. On your VG224 configuration

please remove

voice service voip

fax protocol pass-through g711alaw

modem passthrough nse codec g711alaw

mgcp fax rate 9600

NB: Vg224 with MGCP only supports modem pass-through with nse.

2. Your Vg224 is using the default codec g711ulaw.. but on your cube you have specified g711alaw (modem passthrough nse codec g711alaw)

mgcp modem passthrough voip mode nse (this command without a codec specified uses default G711ulaw)

So one leg from Vg224 will use g711ulaw and other g711alaw..This is not good..

Please configure 'mgcp modem passthrough voip codec g711alaw'

3. remove this config
mgcp fax rate 9600

++++CUBE Config+++++++++

1. You need to remove fax protocol pass-through g711alaw (like I said vg224 does not support this)

so please remove this command from all your dial-peers

2. you need to configure fax rate disable on all your dial-peers

Configure only  "modem passthrough nse codec g711alaw"

Can you do all this and do a test.

Please send the ff: debug

debug ccsip messages

debug voip vtsp all

debug fax relay t30 all-level-1

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