M
ULTICAST
F
ILTERING
3-203
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: Version1 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.
Querier – Device currently serving as the IGMP querier for this
multicast service.