ECS4660-28F_Management Guide-R03

C HAPTER 15 | Multicast Filtering
Layer 2 IGMP (Snooping and Query for IPv4)
– 625 –
◆ Last Member Query Count – The number of IGMP proxy group-
specific or group-and-source-specific query messages that are sent out
before the system assumes there are no more local members.
(Range: 1-255; Default: 2)
This attribute will take effect only if IGMP snooping proxy reporting or
IGMP querier is enabled.
◆ Proxy Query Address – A static source address for locally generated
query and report messages used by IGMP Proxy Reporting.
(Range: Any valid IP unicast address; Default: 0.0.0.0)
IGMP Snooping uses a null IP address of 0.0.0.0 for the source of IGMP
query messages which are proxied to downstream hosts to indicate
that it is not the elected querier, but is only proxying these messages as
defined in RFC 4541. The switch also uses a null address in IGMP
reports sent to upstream ports.
Many hosts do not implement RFC 4541, and therefore do not
understand query messages with the source address of 0.0.0.0. These
hosts will therefore not reply to the queries, causing the multicast
router to stop sending traffic to them.
To resolve this problem, the source address in proxied IGMP query
messages can be replaced with any valid unicast address (other than
the router’s own address).
Rules Used for Proxy Reporting
When IGMP Proxy Reporting is disabled, the switch will use a null IP
address for the source of IGMP query and report messages unless a
proxy query address has been set.
When IGMP Proxy Reporting is enabled, the source address is based on
the following criteria:
■
If a proxy query address is configured, the switch will use that
address as the source IP address in general and group-specific
query messages sent to downstream hosts, and in report and leave
messages sent upstream from the multicast router port.
■
If a proxy query address is not configured, the switch will use the
VLAN’s IP address as the IP source address in general and group-
specific query messages sent downstream, and use the source
address of the last IGMP message received from a downstream host
in report and leave messages sent upstream from the multicast
router port.
WEB INTERFACE
To configure IGMP snooping on a VLAN:
1. Click Multicast, IGMP Snooping, Interface.
2. Select Configure VLAN from the Action list.
3. Select the VLAN to configure and update the required parameters.
4. Click Apply.