Troubleshooting guide

3. Troubleshooting Functional Failures During Operation
44
No. Items to check and
commands
Action
3 If multicast forwarding is not
performed, use the show
igmp-snooping operation
command to check the IGMP
snooping configuration.
Check the following:
- To check whether the IGMP querier that monitors the group
members exists, make sure one of the following messages is
displayed.
(1) If the IGMP querier exists, the IP address of the IGMP querier is
displayed:
IGMP querying system: 192.168.11.20
#
(2) If the IGMP querier does not exist, nothing is displayed for IGMP
querying system:.
IGMP querying system:
- If the Switch is the IGMP querier, make sure the IP address has
been set for the VLAN.
(1) If the IP address has been set for the VLAN, the following
message is displayed:
IP Address: 192.168.11.20
#
(2) If the IP address has not been set for the VLAN, nothing is
displayed for IP Address:.
IP Address:
- If a multicast router is connected, check the mrouter-port setting.
> show igmp-snooping 3253
Date 14.11.08 03:59:14 PM UTC
VLAN counts: 3
VLAN 3253:
IP Address: 192.168.53.100/24 Querier: enable
IGMP querying system: 192.168.53.100
Port (4): 0/13-16
Mrouter-port: 0/13-16
Group counts: 5
4 If multicast forwarding is not
performed, use the show
igmp-snooping group
operation command to check the
IPv4 multicast group address.
Check the following:
- Make sure the joined IPv4 multicast group address is displayed by
the show igmp-snooping group command.
> show igmp-snooping group 3253
Date 14.11.08 04:02:03 PM UTC
Total Groups: 15
VLAN counts: 3
VLAN 3253 Group counts: 5
Group Address MAC Address
230.0.0.11 0100.5e00.000b
Port-list: 0/13
230.0.0.10 0100.5e00.000a
Port-list: 0/13
# If the Switch is the IGMP querier, the same address is displayed for IGMP querying
system and IP Address. If any other device is the IGMP querier, the address displayed for
IGMP querying system is not the same as the address displayed for IP Address.
3.5.6 Multicast forwarding by MLD snooping is not possible
If multicast forwarding is impossible when MLD snooping is used, use the following
analysis flowchart to determine the problem and isolate the cause.