Inter VLAN Routing Overview VLANs control broadcast domain

Inter. VLAN Routing

Overview VLANs control broadcast domain size and keep local traffic local.

Key components of Inter. VLAN Routing • Requirements for Inter. VLAN Routing • VLAN capable switch • Router: External or integrated within a switch • Router to VLAN connection

External Routers • Router-on-a-Stick • Trunk Link Advantages: – Saves router and switch ports…saves money and reduces complexity. – Scales to larger number of VLANs than one-link-per. VLAN design. • Trunk Link Disadvantages: – Additional router overhead – Older IOS versions support limited sets of features on trunked interfaces and may only support ISL trunking encapsulation.

Cisco Layer 3 Feature Cards Router-on-a-stick most appropriate when other options not available. Route switch processors generally adequate unless a high proportion of traffic crosses VLAN boundaries or a large number of gigabit or greater interfaces are present. Switch Fabric Module adds switching capacity. Catalyst 6000 Family Multilayer Switch Feature Card (MSFC 2)

Configuring Inter. VLAN Routing (1) • First task to turn on switch routing functionality. – Switch(config)# ip routing • Switch virtual interface (most common). – Switch#interface vlan 40 – Switch(config-if)# ip address 10. 0. 40. 1 255. 0 • Routed port (turns an Ethernet switch into an Ethernet Router by turning off a switch port functionality). – Switch(config)# interface fa 0/1 – Switch(config-if)# no switchport – Switch(config-if)# ip address 10. 0. 1. 1 255. 0 • The switch port can now be used as a physical router port for connection to an external device such as a router.

Configuring Inter. VLAN Routing (2) • • • RSP(config)#ip routing RSP(config)# interface fa 0/1 RSP(config-if)# no switchport RSP(config)-if# ip address 10. 0. 1. 1 255. 0 Ext(config)# interface fa 0/0 Ext(config-if)# ip address 10. 0. 1. 2 255. 0 Inter. VLAN routing most likely achieved through a virtual interface. As an example, VLAN 10 and VLAN 20 configured on the multi-layer switch. RSP(config)# interface vlan 10 RSP(config-if)# ip address 10. 0. 1 255. 0 RSP(config)# interface vlan 20 RSP(config-if)# ip address 10. 0. 20. 1 255. 0 Don’t forget to enable a routing protocol on both the RSP and External router.

Configuring Inter. VLAN Routing (3)

Verifying Inter. VLAN Routing Configurations • Switch# show ip route • Switch# show ip interface brief • Switch# show ip interface fastethernet module/port – Can show if the port is configured for routing • Switch# show ip interface fastethernet module/port switchport – Either switchport information will be displayed or “Switchport: Disabled” will indicate the port is likely configured for routing.