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:
- Ethernet—ISL or 802.1Q
- ATM—LAN Emulation (LANE) or multiprotocol over ATM (MPOA)
- 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.
Go ahead and configure ISL trunking ...