Compressing Frame Relay Data on a Subinterface

Problem

You want to configure your router to do Frame Relay compression on a subinterface.

Solution

Cisco offers several different types of compression with Frame Relay. You can opt to compress only the TCP headers as follows:

Central#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Central(config)#interface Serial0
Central(config-if)#encapsulation frame-relay
Central(config-if)#frame-relay ip tcp header-compression passive
Central(config-if)#exit
Central(config)#end
Central#

This command also works at the subinterface level:

Central#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Central(config)#interface Serial0.1 point-to-point
Central(config-subif)#frame-relay ip tcp header-compression passive
Central(config-subif)#exit
Central(config)#end
Central#

There are also two different payload compression options. The first uses the FRF.9 Frame Relay compression standard:

Central#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Central(config)#interface Serial0.1 point-to-point
Central(config-if)#frame-relay payload-compression frf9 stac
Central(config-if)#exit
Central(config)#end
Central#

And the second uses Cisco’s proprietary packet-by-packet compression:

Central#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Central(config)#interface Serial0.1 point-to-point
Central(config-if)#frame-relay payload-compression packet-by-packet ...

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