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