Cabletron Systems 2H22 User Manual

Configuring a VLAN on an 802.1Q switch creates a static GVRP entry. 
The entry will always remain registered and will not time out. However, 
dynamic entries will time-out and their registrations are removed from the 
member list if the end station A is removed. This ensures that if switches 
are disconnected, or if end stations are removed, the registered 
information remains accurate.

The end result is that the Port VLAN List of a port is updated with 
information about VLANs that reside off that port, even if the actual 
station on the VLAN is several hops away.

GMRP functions in a similar fashion as GVRP, except that GMRP 
registers multicast addresses on ports. The GMRP uses the multicast 
address (01-80-C2-00-00-20) for controlling the flooding of multicast 
frames. End stations register with the port that they are connected to and 
tell the port which multicast frames they will receive. This is 
accomplished under control of GMRP, which is propagated in VLAN 
context.

The device is capable of supporting multiple filter databases and each 
VLAN is assigned to a database. When GMRP frames are received, they 
may contain a tag or be untagged. 

If the GMRP frame is untagged, the multicast addresses listed in the 
GMRP frame are added to the Port VLAN List of the receiving port. (For 
more information about the Port VLAN List, refer to the Cabletron 
Systems 802.1Q VLAN Users Guide.)

If the GMRP frame is tagged, then the VLAN ID in the tag is used to find 
the filter database to which the multicast address is registered, and then 
the frame is transmitted out the appropriate ports accordingly.