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Cisco IOS in a Nutshell, 2nd Edition by James Boney

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Name

compress — interface

Synopsis

compress {predictor | stac}
no compress {predictor | stac}

Configures

Type of compression used across an interface

Default

None

Description

This command enables compression for the selected interface. Compression can be enabled only for PPP or HDLC encapsulation. Two types of compression are supported:

predictor

Can be used on PPP connections; consumes more of the router’s CPU and memory, but less bandwidth.

stac

Can be used on HDLC or PPP connections; consumes more bandwidth, but requires less CPU power.

Compression should not be activated on lines where link speeds are very high or most of the data is already compressed. If the data is already compressed, the router spends valuable CPU cycles for no reason.

When using compression, monitor the router’s CPU usage. If the CPU usage is consistently high (65%), compression might be hindering the router.

The same type of compression must be enabled on both ends of the link.

Example

The following commands enable stac compression for the serial1 interface, which uses HDLC encapsulation.

interface serial1
  encapsulation hdlc
  compress stac

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