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Cisco ATA 186 and Cisco ATA 188 Analog Telephone Adaptor Administrator’s Guide (H.323)
OL-4008-01
Chapter7 Configuring and Debugging Fax Services
Using Fax Pass-through Mode
Note For detailed information on setting up your IOS gateways and on feature availability, refer to the
document Cisco Fax Services over IP.
Enable Fax Pass-through Mode
The supporting Cisco gateway can enable fax pass-through mode using system-level or dial-peer-level
commands.

System Level commands

Enable the fax pass-through feature using the following system-level commands:
Procedure
Step 1 Run the following command:
voice service voip
Step 2 Run the following command:
modem passthrough NSE [payload-type number] codec {g711µ/law | g711alaw} [redundancy]
[maximum-sessions value]
The definitions of the command parameters a re as follows:
•The payload-type parameter default is 100. Valid values are from 98 to 119.
The NSE payload number must be the same on both the Cisco ATA and the Cisco gateway.
•The codec parameter must be G.711µ−law for faxes sent over a T1 trunk or G.711A-law for faxes
sent over an E1 trunk.
•The redundancy parameter enables RFC 2198 packet redundancy. It is disabled by default.
•The maximum sessions parameter defines the number of simultaneous fax pass-through calls with
redundancy. The default is 16. Valid values are 1 to 26.
When using the voice service voip and modem passthrough nse commands on a terminating gateway
to globally set up fax or modem pass-through with NSEs, you must also ensure that each incoming call
will be associated with a VoIP dial peer to retrieve the global fax or modem configuration. You associate
calls with dial peers by using the incoming called-number command to specify a sequence of digits that
incoming calls can match. You can ensure that all calls will match at least one dial peer by using the
following commands:
Router(config)# dial-peer voice tag voip
Router(config-dial-peer)# incoming called-number .
Step 3 For the Cisco ATA ConnectMode parameter, turn off bits 14 and 15. This enables the sending of fax
pass-through signals and the detection of incoming fax pass-through signals using the Cisco proprietary
method.
Note The NSE payload-type number, fax pass-through codec (G.711µ-law or G.711A-law) and redundancy
parameters must have the same settings for the Cisco ATA that they have for supporting Cisco gateways.