User Manual

DVMRP Overview
274 Enterasys X-Pedition User Reference Manual
L2 Snooping
IGMP L2 snooping allows an XP functioning strictly as a layer-2 switch for a specific VLAN to
actively participate in IGMP traffic forwarding. To enable IGMP snooping on a vlan, use the
following command:
Note: The igmp start-snooping command must be present for the igmp enable vlan command
to function properly. The XP will display VLAN names up to 32 characters in length.
IGMP L2 snooping depends on the presence of an upstream IGMP querier. Whenever it receives an
IGMP query, the XP forwards the query out the appropriate VLAN ports. IGMP snooping allows
per-port traffic patterns in VLANs with multiple ports.
Note: You may not use any L3 configuration on a VLAN that is snooping (e.g., no interfaces
created).
DVMRP Overview
DVMRP is an IP multicast routing protocol. On the XP, DVMRP routing is implemented as
specified in the draft-ietf-idmr-dvmrp-v3-06.txt file, which is an Internet Engineering Task Force
(IETF) document. The XP’s implementation of DVMRP supports the following:
• The mtrace utility, which racks the multicast path from a source to a receiver.
• Generation identifiers, which are assigned to DVMRP whenever that protocol is started on a
router.
• Pruning, which is an operation DVMRP routers perform to exclude interfaces not in the shortest
path tree.
DVMRP uses the Reverse Path Multicasting (RPM) algorithm to perform pruning. In RPM, a
source network rather than a host is paired with a multicast group. This is known as an (S,G) pair.
RPM permits the XP to maintain multiple (S,G) pairs.
On the XP, DVMRP can be configured on a per-interface basis. An interface does not have to run
both DVMRP and IGMP. You can start and stop DVMRP independently from other multicast
routing protocols. IGMP starts and stops automatically with DVMRP. The XP supports up to 64
multicast interfaces.
Note: Because DVMRP and PIM-SM run in separate processes on the XP, current IGMP
functionality may be used only with DVMRP. PIM-SM must use a separate group of
commands called “PIM IGMP.”
To support backward compatibility on DVMRP interfaces, you can configure the router expire time
and prune time on each XP DVMRP interface. This lets it work with older versions of DVMRP.
igmp enable vlan VLAN_NAME