C
ONFIGURING

THE

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WITCH

3-146

•Max Query Response Time – Configures the maximum response time
advertised in IGMP queries. (Range: 0-25 seconds; Default: 10 seconds)
- The switch must be using IGMPv2 for this command to take effect.
- This command defines how long any responder (i.e., client or router)
still in the group has to respond to a query message before the router
deletes the group.
- By varying the Maximum Query Response Time, you can tune the
burstiness of IGMP messages passed on the subnet; where larger
values make the traffic less bursty, as host responses are spread out
over a larger interval.
- The number of seconds represented by the maximum response
interval must be less than the Query Interval.
•Query Interval – Configures the frequency at which host query
messages are sent. (Range: 1-255; Default: 125 seconds)
- Multicast routers send host query messages to determine the interfaces
that are connected to downstream hosts requesting a specific multicast
service. Only the designated multicast router for a subnet sends host
query messages, which are addressed to the multicast address 224.0.0.1.
- For IGMP Version 1, the designated router is elected according to the
multicast routing protocol that runs on the LAN. But for IGMP
Version 2, the designated querier is the lowest IP-addressed multicast
router on the subnet.
•Robustness Variable – Specifies the robustness (i.e., expected packet
loss) for this interface. The robustness value is used in calculating the
appropriate range for other IGMP variables, such as the Group
Membership Interval
(
Last Member Query Interval
)
, as well as the
Other Querier Present Interval, and the Startup Query Count (RFC
2236). (Range: 1-255; Default: 2)
•Version – Configures the IGMP version used on an interface.
(Options: Version 1 or 2; Default: Version 2)
- All routers on the subnet must support the same version. However, the
multicast hosts on the subnet may support either IGMP version 1 or 2.
- The switch must be set to version 2 to enable the Max Query
Response Time.