Local-Area Networks and LAN Switching - CCIE Routing and Switching Exam Certification Guide - page 151

If the router configuration on Router B is changed to virtual ring 10 and DLSw is configured
for RIF Passthru, the RIF reaches the far end ring. The RIF from the host on Router A to Router
B takes the path from Ring 1 to Bridge 5 to Ring 10 to Bridge 6 to Ring 2. The RIF in hex is
0830.0015.00a6.0020.

LAN Switching Topics
Following the CCIE written exam blueprint, this section covers VLAN trunking, CDP, and
forward error correction (FEC). The VLAN trunking methods covered are Inter-Switch Link
(ISL), 802.1q, and Cisco's Virtual Terminal Protocol (VTP).

VLAN Trunking
A VLAN is an association of ports within a switch that serves a group of end stations with a
common set of requirements. All stations in a VLAN share the same IP subnet; therefore, traffic
between VLANs must be routed by an external router or a route-switch module in a Catalyst.
Each VLAN is a logical broadcast domain.

Stations with the same VLAN do not necessarily need to be in the same physical location. You
use trucking schemes to span VLANs throughout LAN switches. Each VLAN runs an instance
of the STP. Figure 4-30 shows logical connectivity between LAN switches and a router.
Because attached stations can be connected to any VLAN, all trunks must include the
configured VLANs. The following sections discuss trunking schemes.

VLAN Trunks Figure 4-30

vlan a
vlan b
vlan c