3Com CoreBuilder 3500, Implementation Manual

Page: 145 / 592

Key Concepts 145
Trunks also enhance network availability, because the Trunk Control
Message Protocol (TCMP) detects and handles physical configuration
errors in the point-to-point configuration. The system automatically
distributes traffic across the ports that are associated with the trunk. If
any of the trunk’s ports go down or up, the system automatically
redistributes traffic across the new arrangement of operational ports.
Key Concepts
Before you configure trunking on your system, become familiar with the
key concepts in this section.
Port Numbering in a
Trunk
When you combine ports on a trunk, the system logically groups the
physical ports that you specify into a single bridge port, identified by a
single bridge port number in bridge statistics. For example, Figure 26
shows that Ethernet ports 2, 3, and 4 are represented by bridge port 2
after trunking.
The lowest numbered port in the trunk, called the anchor port , represents
the entire trunk. After trunking, you can select bridge port 2 when you
specify bridge port or virtual LAN (VLAN) information, but you cannot
select bridge ports 3 or 4 since they are part of the trunk.
Figure 26
Bridge Port Numbering After Trunking
Regardless of whether you define trunking, the physical port numbering
on your system remains the same.
In-band
Network Ports
1 2 3 4 5 6
Ethernet port number (Layer 1):
Trunked Ports
1 2 3 4 5 6
Bridge port number (Layer 2):
2 = Anchor Port