IGMP proxy > Explanation of IGMP proxy

Switch 1 receives the proxied report from switch 3. Switch 1 notes that switch 3 is interested in the group 224.12.13.14 and sends the group multicast to switch 3 on port 49. Output of the command show igmpsnooping shows the membership that switch 1 is aware of.

Manager Switch 1> show igmpsnooping

IGMP Snooping

------------------------------------------------------------------------

Status

Enabled

Disabled All-groups ports

None

Vlan Name (vlan id) ..... default (1)

Group List

 

No group memberships.

 

Vlan Name (vlan id) ..... vlan200 (200)

Group List

 

Group. 224.12.13.14

Entry timeout 182 secs

Ports 49

 

------------------------------------------------------------------------

When a client leaves a group

When the client on switch 2 wants to stop receiving the group’s multicast stream, it sends an IGMP Leave message. The switches use the above process to transfer the message to switch 1.

Note the following points about how IGMP Proxy deals with Leave messages:

zThe Proxy sends an IGMP Leave Group message via its upstream interface only when the last interface on the Proxy leaves the group.

zThe Proxy does not respond to IGMP Join or Leave Group messages received via its upstream interface, but only to those received via downstream interfaces.

zThe Proxy does respond to IGMP query messages received via its upstream interface. When the Proxy—switch 3 in this example—sends a Leave Group message upstream, the upstream IGMP Querier—switch 1—sends a membership query. Switch 3 takes that query and proxies it to the downstream interface, vlan100, with its own IP as the source (172.31.0.253). This means any other interested clients on switch 2 can declare their interest in continuing to receive the multicast stream.

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Allied Telesis AR400 manual Group Entry timeout 182 secs Ports, AlliedWare OS How To Note Igmp