Trunking Overview - Cisco 6500 Series Software Configuration Manual

Chapter 7 Configuring LAN Ports for Layer 2 Switching

Trunking Overview

For information about VLANs, see
Note
A trunk is a point-to-point link between the switch and another networking device. Trunks carry the
traffic of multiple VLANs over a single link and allow you to extend VLANs across an entire network.
Two trunking encapsulations are available on all Ethernet ports:
•
•
You can configure a trunk on a single Ethernet port or on an EtherChannel. For more information about
EtherChannel, see
Ethernet trunk ports support several trunking modes (see
whether the trunk uses ISL or 802.1Q encapsulation, and if the encapsulation type is autonegotiated.
You can configure LAN ports to negotiate the encapsulation type. You cannot configure WAN interfaces
Note
to negotiate the encapsulation type.
The Dynamic Trunking Protocol (DTP) manages trunk autonegotiation on LAN ports. DTP supports
autonegotiation of both ISL and 802.1Q trunks.
To autonegotiate trunking, the LAN ports must be in the same VTP domain. Use the trunk or
nonegotiate keywords to force LAN ports in different domains to trunk. For more information on VTP
domains, see
78-14099-04
Inter-Switch Link (ISL)—ISL is a Cisco-proprietary trunking encapsulation.
The following switching modules do not support ISL encapsulation:
Note
• WS-X6501-10GEX4
• WS-X6502-10GE
• WS-X6548-GE-TX
• WS-X6548V-GE-TX
• WS-X6148-GE-TX
• WS-X6148V-GE-TX
802.1Q—802.1Q is an industry-standard trunking encapsulation.
Chapter 13, "Configuring EtherChannels."
Chapter 8, "Configuring VTP."
Catalyst 6500 Series Switch Cisco IOS Software Configuration Guide—Release 12.1 E
Chapter 9, "Configuring VLANs."
Table 7-2 on page
Understanding How Layer 2 Switching Works
7-4). You can specify
7-3