Trunk Control Message Protocol (Tcmp) - 3Com corebuilder 3500 Implementation Manual

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HAPTER RUNKING
Trunk Control
Message Protocol
(TCMP)
It is important to understand the relationships between Ethernet, bridge,
and VLAN port-related information:
Ethernet port information — Each physical port is always listed
individually, regardless of whether it is part of a trunk.
Bridge port information — This information uses the concept of
bridge ports. When you perform bridge port operations, you specify
the trunk's anchor port, not the other ports in the trunk, as the
representative bridge port. In the bridge port displays, each selectable
bridge port has a port field that contains multiple port numbers if the
bridge port represents a trunk (for example,
VLAN information — When you define VLANs (as described in
Chapter 9), you must specify the bridge ports that you want to be part
of the VLAN. If you have a trunk, you specify its anchor port as the
bridge port. The VLAN that you create then includes all of the physical
ports in the trunk.
The Trunk Control Message Protocol (TCMP) performs the following
functions:
Detects and corrects trunks that violate trunk configuration rules
Ensures orderly activation and deactivation of trunk ports
The system runs a separate TCMP agent for each trunk. If TCMP detects
an invalid configuration, the protocol restricts the trunk to the largest
subset of ports that is a valid configuration.
Enabling TCMP is optional, but recommended. If TCMP is disabled, the
network still functions, but without automatic trunk validation and
reconfiguration. By default, TCMP is enabled.
Each TCMP agent:
Periodically transmits a TCMP helloMessage through every trunk port.
Continuously listens for helloMessages from other trunk ports.
Builds a list of ports that TCMP has detected.
Uses this list to activate or deactivate trunk ports to maintain valid
trunk configurations.
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