ip rtp coalesce Command

To allow header compression to correctly decompress packets that are destined for digital signal processors (DSPs), use the ip rtp coalesce command in global configuration mode. To turn off the feature, use the no form of this command.

Release Modification

12.2(10)

This command was introduced on all Cisco IOS platforms.

12.2(11)T

This command was integrated into Cisco IOS Release 12.2(11)T for use on Cisco 7200 series platforms only.

Release	Modification
12.2(10)	This command was introduced on all Cisco IOS platforms.
12.2(11)T	This command was integrated into Cisco IOS Release 12.2(11)T for use on Cisco 7200 series platforms only.

This command allows header compression to work with some DSPs that do not correctly support Cisco fast-switched packets.

This command is either enabled or disabled. This command is designed to prevent memory overload when the connection trunk command is used and fast switching is enabled with compressed Real-Time Transport Protocol (RTP).

Some DSPs periodically display the following message on the console and pause indefinitely:

This symptom is triggered when compressed Real-Time Transport Protocol (cRTP) is configured on a WAN link that exists between the two voice gateways when a connection trunk is configured for voice services and when fast switching is enabled on the interface that has cRTP configured.

Some DSPs cannot handle multiple particles, so you can use the ip rtp coalesce global configuration command to allow the header to be written into the data particle. Using this command allows fast switching to remain enabled on the cRTP interfaces and does not increase the CPU load appreciably above normal fast-switching cRTP levels. This symptom does not occur if process-switched cRTP is used.

You can also work around this situation by discontinuing cRTP or disabling fast switching on the WAN interface by entering the no ip route-cache interface configuration command.

For more information about fast-switched RTP header compression and the ip rtp coalesce command, refer to CSCdw76315. You can access the Bug Toolkit by using the following link:

The following sample configuration allows header compression to correctly decompress packets that are destined for DSPs that do not correctly support multiparticle packets. This function leaves fast-switching enabled on the cRTP interfaces.

Command Description

connection trunk

Specifies a connection that emulates a permanent trunk connection to a PBX.

ip route-cache

Controls the use of high-speed switching caches for IP routing.

Command	Description
connection trunk	Specifies a connection that emulates a permanent trunk connection to a PBX.
ip route-cache	Controls the use of high-speed switching caches for IP routing.

Table of Contents

ip rtp coalesce Command