Allied Telesis 2.6.1 manual Interfaces to Layer 3 Protocols, Igmp Snooping

Layer 2 Switching		97
	Table 20: Parameters in the output of the SHOW STP COUNTER command
	Parameter	Meaning
	Config BPDU length	The number of Configuration BPDUs that had an incorrect
		length.
	TCN BPDU length	The number of Topology Change Notification BPDUs that
		had an incorrect length.
	RST BPDU length	The number of Rapid Spanning Tree BPDUs that had an
		incorrect length (RAPID mode only).

If necessary, all the STP configuration that users have created on the switch can be removed, so that all STPs except the default STP are destroyed, and all other defaults are restored, using the command:

PURGE STP

The PURGE STP command should be used with caution, and generally only before major reconfiguration of the switch, as it removes all STP configuration entered on the switch.

Interfaces to Layer 3 Protocols

Interfaces can be configured to VLANs for IP, IPX and Appletalk routing protocols in the same way that other interfaces are created for other interface types. Concatenate VLAN with the VID of the VLAN giving VLANn, for instance:

INTERFACE=VLAN3

IGMP Snooping

IGMP (Internet Group Management Protocol) is used by IP hosts to report their multicast group memberships to routers and switches. IP hosts join a multicast group to receive broadcast messages directed to the multicast group address. IGMP is an IP-based protocol and uses IP addresses to identify both the multicast groups and the host members. For a VLAN-aware devices, this means multicast group membership is on a per-VLAN basis. If at least one port in the VLAN is a member of a multicast group, by default multicast packets will be flooded onto all ports in the VLAN.

IGMP snooping enables the switch to forward multicast traffic intelligently on the switch. The switch listens to IGMP membership reports, queries and leave messages to identify the switch ports that are members of multicast groups.

Multicast traffic will only be forwarded to ports identified as members of the specific multicast group.

IGMP snooping is performed at Layer 2 on VLAN interfaces automatically. By default, the switch will only forward traffic out those ports with multicast listeners, therefore it will not act as a simple hub and flood all multicast traffic

Software Release 2.6.1 C613-02039-00 REV A