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20-4 User Guide for the Avaya P580 and P882 Multiservice Switches, v6.1
Chapter 20
The Dissemination
Process, LGMP
and CGMP
Snooping
The Dissemination Process provides a method to dynamically configure
multicast sessions on switches with VLANs that do not have IP interfaces.
See Figure 20-1.
Figure 20-1. LGMP and CGMP Snooping
Switch 1 will route the multicast traffic from the Multicast Server on VLAN
1 to VLAN 2. Switch 2 does not have an IP interface on VLAN 2. Because
the Learning Process requires an IP interface to perform learning, a different
method must be used to create multicast sessions on Switch 2. Switch 1
must disseminate the Intelligent Multicast information to all switches on the
attached VLANs that do not have IP interfaces. Two protocols are available
for this use on the Switch, LGMP and CGMP.
LGMP and CGMP are similar protocols. Both protocols have a server
implementation that runs on a switch that implements the Learning Process,
and both protocols have a client implementation which runs on switches
that do not have local IP interfaces on all involved VLANs. For the Avaya
Multiservice switch, only the client implementation of CGMP is available
in case the switch is connected to a Cisco router. This implementation is
called CGMP Snooping.
* Note: IGMP Snooping must be enabled to learn the sessions that the
LGMP server will disseminate. An LGMP server is active only
for VLANs that have an IGMP interface enabled.