The following is an example of a multicast route trace:
SR# mtrace
80.0.0.10 30.0.0.1 227.0.0.1 Type escape sequence to abort
Querying full reverse path... 0 30.0.0.1 - 1 50.0.0.1 PIM - 2 50.0.0.4
- 3 70.0.0.4 PIM - 4 70.0.0.5 - 5 80.0.0.5 PIM [PRUNE SENT]
Use the following CLI show commands to determine which interfaces on the router have
multicast routing enabled: show ip mvif show ipv6 mvif
You must enable multicast routing at the global level. If you do not enable multicast routing
globally, the multicast routing protocols do not become operational even if you enable individual
protocols. Use the following command to enable multicast routing at the global level: SR/
configure# ip multicast-routing (IPv4) SR/configure# ipv6 multicast-
routing (IPv6)
Use the following commands to determine the multicast forwarding entries currently in use
(that is, for traffic that is being forwarded): show ip mroute <source or group ipaddr>
[summary] show ipv6 mroute <group ipaddr> [summary]
The command has options to filter based on the source and the group. The following are
examples of the show ip mroute command for an IPv4 network:
•
show ip mroute 10.0.0.1
•
show ip mroute 10.0.0.1 229.0.0.1
•
show ip mroute 229.0.0.1
•
show ip mroute 229.0.0.1 10.0.0.1
The preceding show command provides details of the multicast forwarding entry including the
incoming interface, the list of outgoing interfaces, as well as when the entry was created. The
"up" time and expiry time is useful for determining how long the entry has been active, and for
detecting disruptions.
Note that even though the multicast path may be set up in the multicast routing protocol control
path, the multicast forwarding entry is created only when data actually starts to flow.
Use the "summary" option with the preceding show command for an overview of the multicast
forwarding entries.
When troubleshooting multicast forwarding, it can be necessary to clear all entries or certain
specific entries. This is very useful as a workaround for issues where entries are caught in an
inconsistent state. Clearing entries triggers a clean state setup. Enter the following commands
to clear all entries: clear ip mroute all clear ipv6 mroute all
Enter the following commands to clear specific entries: clear ip mroute <group
ipaddr> [source ipaddr] clear ipv6 mroute <group ipaddr> [source
ipaddr]
The following are examples of the clear ip mroute command for an IPv4 network:
•
clear ip mroute 229.0.0.1
•
clear ip mroute 229.0.0.1 10.0.0.1
The clear ip mroute command not only deletes the entries in the forwarding plane, but
also ensures that the corresponding states in the multicast routing protocol (viz. DVMRP and
Troubleshooting IPv4 and IPv6 multicast routing
154 Troubleshooting August 2013
Comments? infodev@avaya.com
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