You must configure a VoIP dial peer on both the originating and terminating gateways to match the call--for example, using a destination pattern.
When the system keyword is entered, the following parameters are not available: nse, payload-type, codec, and redundancy. The configuration is taken from the modem passthrough nsecommand in voice-service configuration mode.
When modem passthrough is configured for a specific dial peer, the dial-peer configuration takes precedence over the global configuration.
Use the following steps to configure modem passthrough for a specific dial peer.