Allied Telesis AR400 - Manual (Page 28)

Page 28 | AlliedWare™ OS How To Note: IGMP
Query solicitation (rapid recovery from topology changes) > Why convergence takes so long without query solicitation
Why convergence takes so long without query
solicitation
This section illustrates IGMP convergence in a simple network that does not need STP
because it has no switch loops. Query Solicitation is disabled by default in networks like this,
because no switch is an STP root bridge or an EPSR master node.
In this network, it takes up to 125 seconds for multicasting to recover after a port comes
back up. This section explains the reason for the slow convergence.
"Speeding up IGMP
convergence in a non-looped topology" on page 33 explains the solution.
Example
The following figure shows the network for the example in this section.
The example considers what happens when a port comes up. When the port was down, the
client stopped receiving multicasts, because there was no backup route available. The
example shows how the network recovers. The multicast group is 224.12.13.14.
Switch 1 is configured with IGMP, which makes it the IGMP Querier in this network.
Switch 2 is an IGMP Snooper. It forwards multicast packets and IGMP messages as required.
IGMP snooping is enabled by default and does not need any configuration.
X Configure switch 1
set system name="Switch 1"
# IP configuration
enable ip
add ip int=vlan1 ip=10.13.2.191 mask=255.255.255.0
enable ip igmp
enable ip igmp int=vlan1
X Configure switch 2
set system name="Switch 2"
# IP configuration
enable ip
add ip int=vlan1 ip=10.13.2.193 mask=255.255.255.0
Multicast Server
Rapier 24i
Switch 1:
Querier
Rapier 24i
Switch 2:
Snooper
Client 1
port 9
port 1 port 1
port 24
igmp-no-qs.eps