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Troubleshooting IP Multicast Switching (IPMS) Troubleshooting a Device that Drops Out of an IP Multicast Stream
OmniSwitch Troubleshooting Guide September 2005 page 14-3
Troubleshooting a Device that Drops Out of an IP
Multicast Stream
If the issue is a device can actually join a multicast stream, but loses it after a period of time, there are a
few items to check. First, does the device lose the stream when the Expiry timer reaches zero in the show
ip multicast groups command?
-> show ip multicast groups
Destination IP Source IP VLAN Slot/Port Expire
--------------------+--------------------+----+---------+------
224.0.0.9 10.10.10.50 1 5/23 242
224.0.1.22 10.10.10.65 1 5/23 239
224.0.1.24 10.10.10.5 1 5/23 235
224.77.1.0 10.10.10.64 1 5/15 235
224.77.205.58 10.10.10.64 1 5/15 234
239.255.255.250 10.10.10.66 1 5/23 236
239.255.255.254 10.10.10.5 1 5/23 235
239.255.255.254 10.10.10.70 1 5/23 260
Once this timer reaches zero, the switch will stop sending the multicast stream to this port, as it believes
there are no longer any devices requesting it. This could happen if in the VLAN where the device
connects, an IP multicast router does not exist. The multicast client will send IGMP messages on layer 3,
and if the VLAN has no L3 instance, there is no way for it to listen to those messages. It is then recom-
mended to have at least one IP multicast router configured and enabled on the VLAN.
Issue a show vlan command to check the configuration of the VLAN. For example:
-> show vlan 1
Name : VLAN 1,
Administrative State: enabled,
Operational State : disabled,
Spanning Tree State : enabled,
Authentication : disabled,
IP Router Port : none,
IPX Router Port : none
Assign the VLAN an IP address that is proper for your network:
-> vlan 1 router ip 10.10.10.7 mask 255.255.255.0
Then reissue the show vlan command to verify:
-> show vlan 1
Name : VLAN 1,
Administrative State: enabled,
Operational State : disabled,
Spanning Tree State : enabled,
Authentication : disabled,
IP Router Port : 10.10.10.7 255.255.255.0 forward e2,
IPX Router Port : none
Now that an IP address has been assigned, recheck the show ip multicast groups command and verify
that the slot/port in question has an entry. You should see the timer decrement and reset as described
above.