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Allied Telesis AR400 User Manual

Page 29

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Page 29 | AlliedWare™ OS How To Note: IGMP

Query solicitation (rapid recovery from topology changes) > Why convergence takes so long without query solicitation

Explanation from the perspective of switch 2, the snooper

When link

is up

When the link is connected (all ports are up), the Snooper has entries for two ports:

z

port 9, which is the Snooper’s connection to the client. The Snooper sends the multicast
stream out this port, as well as sending Queries (the Snooper floods Queries out all its
ports)

z

port 1, which is the Snooper’s connection to the Querier. This is an All Groups entry, so
the Snooper forwards Reports out this port.

The output of the command show igmpsnooping shows both entries.

When link

goes down

When we disconnect port 1 on the Snooper, the All Groups entry disappears.

The Snooper still knows to send Queries and the multicast stream out port 9. However, it
does not know where to send any IGMP Report messages.

Manager Switch 2> show igmpsnooping

IGMP Snooping

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

Status ........................... Enabled

Disabled All-groups ports ........ None

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

Fast Leave .............. Off

Query Solicitation ...... Off

Static Router Ports ..... None

Group List ..............

Group. 224.12.13.14 Entry timeout 228 secs

Ports 9

All Groups Entry timeout 232 secs

Ports 1

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

Manager Switch 2> show igmpsnooping

IGMP Snooping

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

Status ........................... Enabled

Disabled All-groups ports ........ None

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

Fast Leave .............. Off

Query Solicitation ...... Off

Static Router Ports ..... None

Group List ..............

Group. 224.12.13.14 Entry timeout 196 secs

Ports 9

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

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