What are the five steps to configure routing on a Layer 3 switch that connects to an external router?

Configure the routed port with no switchport, enable routing with ip routing, configure a routing protocol (e.g., OSPF (Open Shortest Path First)), verify with show ip route, and test with ping.

Step 1 — Configure the routed port:

D1(config)# interface G1/0/1
D1(config-if)# no switchport
D1(config-if)# ip address 10.10.10.2 255.255.255.0
D1(config-if)# no shut

Step 2 — Enable IP (Internet Protocol) routing:

D1(config)# ip routing

Step 3 — Configure a routing protocol (e.g., OSPF):

D1(config)# router ospf 10
D1(config-router)# network 192.168.10.0 0.0.0.255 area 0
D1(config-router)# network 192.168.20.0 0.0.0.255 area 0
D1(config-router)# network 10.10.10.0 0.0.0.255 area 0

Step 4 — Verify routing:

D1# show ip route

Step 5 — Test connectivity:

D1# ping 10.10.10.1

The routing protocol advertises the VLAN (Virtual Local Area Network) subnets so external routers know how to reach them. Without this, only devices directly connected to the Layer 3 switch can communicate across VLANs.

Go deeper:

• Inter-VLAN Routing using Layer 3 Switches (Cisco Press) — the routed-port-to-external-router scenario including no switchport and advertising VLAN subnets.