Configuring Vlan Trunks; Trunking Overview - Cisco 2950G 24 - Catalyst Switch Software Configuration Manual

Chapter 14 Configuring VLANs

Configuring VLAN Trunks

These sections describe how VLAN trunks function on the switch:
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Trunking Overview

A trunk is a point-to-point link between one or more Ethernet switch interfaces and another networking device
such as a router or a switch. Fast Ethernet and Gigabit Ethernet trunks carry the traffic of multiple VLANs
over a single link, and you can extend the VLANs across an entire network.
Figure 14-2
Figure 14-2 Catalyst 2950, 2900 XL, and 3500 XL Switches in a 802.1Q Trunking Environment
You can configure a trunk on a single Ethernet interface or on an EtherChannel bundle. For more
information about EtherChannel, see
Ethernet trunk interfaces support different trunking modes (see
trunking or nontrunking or to negotiate trunking with the neighboring interface. To autonegotiate
trunking, the interfaces must be in the same VTP domain.
Trunk negotiation is managed by the Dynamic Trunking Protocol (DTP), which is a Point-to-Point
Protocol. However, some internetworking devices might forward DTP frames improperly, which could
cause misconfigurations.
78-14982-01
Trunking Overview, page 14-15
802.1Q Configuration Considerations, page 14-16
Default Layer 2 Ethernet Interface VLAN Configuration, page 14-17
shows a network of switches that are connected by 802.1Q trunks.
802.1Q 802.1Q
trunk
Catalyst
2900 XL
switch
Catalyst
3500 XL
switch
VLAN1
VLAN2
Catalyst 6000 series
switch
802.1Q
trunk trunk
Catalyst
2950
switch
VLAN3
VLAN1
Chapter 27, "Configuring EtherChannels."
Catalyst 2950 Desktop Switch Software Configuration Guide
Configuring VLAN Trunks
802.1Q
trunk
Catalyst
3500 XL
switch
VLAN2
VLAN3
Table 14-4). You can set an interface as
14-15