© 2006 Cisco Systems, Inc. All rights reserved. BCMSN v Implementing Inter-VLAN Routing Describing Routing Between VLANs

© 2006 Cisco Systems, Inc. All rights reserved. BCMSN v Inter-VLAN Routing with External Router Single trunk link carries traffic for multiple VLANs to and from router.

© 2006 Cisco Systems, Inc. All rights reserved. BCMSN v Inter-VLAN Routing External Router Configuration Commands Configure on subinterface encapsulation dot1Q (or isl) 10 ip address Verify show vlan 10 show ip route

© 2006 Cisco Systems, Inc. All rights reserved. BCMSN v Inter-VLAN Routing on External Router: 802.1Q Trunk Link

© 2006 Cisco Systems, Inc. All rights reserved. BCMSN v Inter-VLAN Routing on External Router: ISL Trunk Link

© 2006 Cisco Systems, Inc. All rights reserved. BCMSN v Verifying Inter-VLAN Routing The ping command tests connectivity to remote hosts.

© 2006 Cisco Systems, Inc. All rights reserved. BCMSN v Verifying the Inter-VLAN Routing Configuration Router#show ip interface brief Displays the current IP configuration per VLAN Router#show ip route Displays IP route table information Router#show vlan Displays IP address on interfaces and current state of interface

© 2006 Cisco Systems, Inc. All rights reserved. BCMSN v Explaining Multilayer Switching

© 2006 Cisco Systems, Inc. All rights reserved. BCMSN v Layer 2 Switch Forwarding Process

© 2006 Cisco Systems, Inc. All rights reserved. BCMSN v Logical Packet Flow for a Multilayer Switch

© 2006 Cisco Systems, Inc. All rights reserved. BCMSN v Rewritten IP Unicast Packet IP Unicast Frame and Packet Rewrite Incoming IP Unicast Packet

© 2006 Cisco Systems, Inc. All rights reserved. BCMSN v CAM Table Requires an exact match on all bits Matching is a binary operation: 0 or 1 Provides very high- speed lookups

© 2006 Cisco Systems, Inc. All rights reserved. BCMSN v TCAM Table Matches only significant values Matches based on three values: 0, 1, or X (either) Masks used to wildcard some content fields

© 2006 Cisco Systems, Inc. All rights reserved. BCMSN v Summary A router on a stick can be used to route between VLANs using either ISL or 802.1Q as the trunking protocol. A router on a stick requires subinterfaces, one for each VLAN. Verify inter-VLAN routing by generating IP packets between two subnets. Multilayer switches can forward traffic at both Layer 2 and Layer 3. Multilayer switches rewrite the Layer 2 and Layer 3 header using tables held in hardware.

© 2006 Cisco Systems, Inc. All rights reserved. BCMSN v