Allied Telesis AR400 manual Why convergence takes so long without query solicitation, Example

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.

	Multicast Server
		Client 1
	port 24	port 9
Switch 1:	port 1	port 1	Switch 2:
Querier			Snooper
	Rapier 24i	Rapier 24i
			igmp-no-qs.eps

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.

XConfigure switch 1

Switch 1 is configured with IGMP, which makes it the IGMP Querier in this network.

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

XConfigure switch 2

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.

set system name="Switch 2"

#IP configuration enable ip

add ip int=vlan1 ip=10.13.2.193 mask=255.255.255.0

Page 28 AlliedWare™ OS How To Note: IGMP