Cisco Systems 78-11741-02 manual RTP Header Compression Examples, IPC-451

Configuring IP Multicast Routing

IP Multicast Configuration Examples

Inconsistent candidate RP selection between Cisco and non-Cisco RFC 2362-compliant routers in the same domain if multiple candidate RPs with partially overlapping group address ranges are configured can occur. Inconsistent candidate RP selection can lead to disconnectivity between sources and receivers in the PIM domain. A source may register with one candidate RP and a receiver may connect to a different candidate RP even though it is in the same group.

The following example shows a configuration that can cause inconsistent RP selection between a Cisco and a non-Cisco router in a single PIM domain with PIM Version 2 BSR:

access-list 10 permit 224.0.0.0 7.255.255.255

ip pim rp-candidate ethernet1 group-list 10 priority 20

access-list 20 permit 224.0.0.0 15.255.255.255

ip pim rp-candidate ethernet2 group-list 20 priority 10

In this example, a candidate RP on Ethernet interface 1 announces a longer group prefix of 224.0.0.0/5 with a lower priority of 20. The candidate RP on Ethernet interface 2 announces a shorter group prefix of 224.0.0.0/4 with a higher priority of 10. For all groups that match both ranges a Cisco router will always select the candidate RP on Ethernet interface 1 because it has the longer announced group prefix.

Anon-Cisco fully RFC 2362-compliant router will always select the candidate RP on Ethernet interface 2 because it is configured with a higher priority.

To avoid this interoperability issue, do not configure different candidate RPs to announce partially overlapping group address prefixes. Configure any group prefixes that you want to announce from more than one candidate RP with the same group prefix length.

The following example shows how to configure the previous example so that there is no incompatibility between a Cisco router and a non-Cisco router in a single PIM domain with PIM Version 2 BSR:

access-list 10 permit 224.0.0.0 7.255.255.255

ip pim rp-candidate ethernet1 group-list 10 priority 20

access-list 20 permit 224.0.0.0 7.255.255.255 access-list 20 permit 232.0.0.0 7.255.255.255

ip pim rp-candidate ethernet2 group-list 20 priority 10

In this configuration the candidate RP on Ethernet interface 2 announces group address 224.0.0.0/5 and 232.0.0.0/5 which equal 224.0.0.0/4, but gives the interface the same group prefix length (5) as the candidate RP on Ethernet 1. As a result, both a Cisco router and an RFC 2362-compliant router will select the RP Ethernet interface 2.

RTP Header Compression Examples

The following example enables RTP header compression for a serial, ISDN, or asynchronous interface. For ISDN, you also need a broadcast dialer map.

interface serial 0 :or interface bri 0 ip rtp header-compression encapsulation ppp

ip rtp compression-connections 25

The following Frame Relay encapsulation example shows how to enable RTP header compression on the specified map.

interface serial 0

ip address 1.0.0.2 255.0.0.0 encapsulation frame-relay

Cisco IOS IP Configuration Guide

IPC-451