Trunking

Routing provides inter-VLAN connectivity, whereas trunking provides intra-VLAN connectivity. Trunks, whether between switches, from a router to a switch, or from a switch to a file server, minimize the number of interfaces and cables to transport multi-VLAN traffic.

There are various methods of multiplexing VLANs in trunking:

  • Cisco

    - Ethernet—ISL or 802.1Q

    - FDDI—802.10

    - ATM—LAN Emulation (LANE) or multiprotocol over ATM (MPOA)

  • Mixed-vendor environment

    - 802.1Q

    - LANE or MPOA

Cisco uses its own proprietary ISL and the standards-based IEEE 802.1Q for trunking. (See Figure 7-4.) However, Cisco has started to favor 802.1Q over ISL. Some newer switches such as the 2950 support only 802.1Q.

Figure 7-4. Trunking

Go ahead and configure ISL trunking ...

Get CCNP Practical Studies: Troubleshooting now with the O’Reilly learning platform.

O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.

Start your free trial