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lordshawn
Beginner

Fax Quality Issues and Troubleshooting

Running 2821 with 4FXO and 2FX VWIC2 and VWic3's.

CUCM 7.1.6

Issue is some of my sites have poor line quality. Sometimes i can replace the lines and it fixes the issues.  Is there any commands on IOS i can use to adapt for line quality issues? I use g711 always for faxing.

Any suggestions?

Thanks.

1 REPLY 1
Marcel Ammann
Participant

Hello,

I think you have CUCM Version 7.1.5

You can try to configure T.38 on your Voice Gateways on the sites:

http://www.cisco.com/en/US/docs/voice_ip_comm/uc_system/UC5.0.1/ipt_system_arch/COL_FMT.html

or:

http://www.cisco.com/en/US/docs/ios/12_3/vvf_c/cisco_ios_fax_services_over_ip_application_guide/t38.html

Configuration example:

Step 1

voice service voip

Example:

Router(config)# voice service voip

Enters voice-service configuration mode.

Step 2

fax protocol t38 [nse [force]] [ls-redundancy value [hs-redundancy value]] [fallback {cisco | none | pass-through {g711ulaw | g711alaw}}]

Example:

Router(config-voi-serv)# fax protocol t38 ls-redundancy 0 hs-redundancy 0 fallback pass-through g711ulaw

Specifies the fax protocol for all VoIP dial peers. Keywords and arguments are as follows:

nse—(Optional) Use of Cisco named service events (NSEs) for fax signaling.

force—(Optional) Required use of NSEs for fax signaling, which permits interworking of H.323 or SIP gateways with MGCP gateways for T.38 fax relay.

ls-redundancy—(Optional) Number of redundant T.38 fax packets to be sent for the low-speed V.21-based T.30 fax machine protocol. Range varies by platform from 0 (no redundancy) to 5 or 7. For details, see CLI help. Default: 0.

hs-redundancy—(Optional) Number of redundant T.38 fax packets to be sent for high-speed V.17, V.27, and V.29 T.4 or T.6 fax machine image data. The value range varies by platform from 0 (no redundancy) to 2 or 3. For details, see CLI help. Default: 0.

Note Setting the hs-redundancy parameter greater than 0 causes a significant increase in the network bandwidth consumed by the fax call.

Step 3

exit

Example:

Router(config-voi-serv)# exit

Exits voice-service configuration mode.

Also here is a nice posting in the forum: Fax Configuration and Troubleshooting Project =>

https://supportforums.cisco.com/community/netpro/collaboration-voice-video/ip-telephony/blog/2010/10/26/fax-configuration-and-troubleshooting-project

Please rate helpful posts.

Kind regards,

Marcel Ammann

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