Specifications

cGVRP
Information About cGVRP
2
• cGVRP and Connectivity Fault Management(CFM) can coexist but if the line card (LC) or
supervisor does not have enough mac-match registers to support both protocols, the cGVRP ports
on those LCs are put in error disabled state. To use Layer 2 functionality, disable cGVRP on those
ports and configure shut/no shut.
• cGVRP functionality applies only to interfaces configured for Layer 2 (switchport) functionality.
• Native VLAN Tagging causes frames sent to the native VLAN of the .1Q trunk ports to be
encapsulated with .1Q tags. Problems may arise with other GVRP participants on the LAN because
they may not be able to admit tagged GVRP PDUs. Caution must be exercised if both features are
enabled at the same time.
• 802.1X authentication and authorization takes place after the port becomes link-up and before the
Dynamic Trunking Protocol (DTP) negotiations start prior to GVRP running on the port.
• Port Security works independently from GVRP and it may be limited to the number of other GVRP
participants on a LAN that a GVRP enabled port on a device can communicate with.
• GVRPs cannot be configured and run on a sub-interface.
• GVRP and UniDirectional Link Routing (UDLR) should not be enabled on the same interface
because UDLR limits frames in one direction on the port and GVRP is a two way communication
protocol.
• Additional memory is required to store GARP/GVRP configurations and states per GVRP enabled
port, but it can be dynamically allocated on demand.
• GARP Multicast Registration Protocol (GMRP) is not supported.
Information About cGVRP
To configure cGVRP, you should understand the following concepts:
• GARP/GVRP Definition, page 2
• cGVRP Overview, page 2
• How to Configure cGVRP, page 4
GARP/GVRP Definition
GVRP enables automatic configuration of switches in a VLAN network allowing network devices to
dynamically exchange VLAN configuration information with other devices. GVRP is based on GARP
which defines procedures for registering and deregistering attributes with each other. It eliminates
unnecessary network traffic by preventing attempts to transmit information to unregistered users.
GVRP is defined in IEEE 802.1Q.
cGVRP Overview
GVRP is a protocol that requires extensive CPU time in order to transmit all 4094 VLAN states on a
port. In Compact mode only one PDU is sent and it includes the states of all the 4094 VLANs on a port.
VLAN pruning can be accomplished faster by running in a special mode, Fast Compact Mode, and on
point-to-point links.