How to configure routing on an access layer switch

Routing on an access layer switch is enabled by configuring Layer 3 interfaces (SVIs or routed ports) and enabling IP routing to allow inter-VLAN communication.

Enable Layer 3 Functionality

To configure routing on a Layer 3 switch, you first need to enable IP routing. On Cisco switches, this can be done using the ip routing command in global configuration mode. Some models, like the 2960-XR, may require adjusting the SDM template with sdm prefer lanbase-routing and reloading the switch to allocate resources for Layer 3 routing . Meraki switches allow enabling Layer 3 routing through the dashboard under Switching > Configure > Routing & DHCP .

Configure Switched Virtual Interfaces (SVIs)

SVIs act as Layer 3 interfaces for each VLAN. Steps include:

1. Create a VLAN interface: interface vlan
2. Assign an IP address and subnet mask: ip address
3. Ensure the VLAN exists and has active ports assigned. Only VLANs with configured SVIs can route traffic . For example, VLAN 10 with IP 192.168.1.1/24:

interface vlan 10 ip address 192.168.1.1 255.255.255.0 no shutdown

Configure Routed Ports (Optional)

Physical interfaces can be converted to routed ports to act as Layer 3 interfaces:

interface gigabitEthernet 1/0/1 no switchport ip address 10.0.0.1 255.255.255.0 no shutdown

Routed ports are useful for uplinks to other Layer 3 devices or for point-to-point links .

Set Default or Static Routes

To allow traffic to leave the switch to other networks, configure a default route:

ip route 0.0.0.0 0.0.0.0

This ensures packets destined for unknown subnets are forwarded to the appropriate router or core switch .

Verification

After configuration, verify routing functionality:

• show ip route – displays the routing table and connected routes.
• ping – tests inter-VLAN connectivity.
• show vlan brief – confirms VLANs are active and assigned to ports.

Best Practices

• Only enable Layer 3 routing on switches that support it to avoid performance issues .
• Use SVIs for inter-VLAN routing within the switch and routed ports for uplinks or point-to-point connections.
• Ensure each host uses the correct SVI IP as its default gateway for proper routing .
• Consider using dynamic routing protocols like OSPF or EIGRP in larger campus networks for scalability and redundancy . By following these steps, an access layer switch can perform both Layer 2 switching and Layer 3 routing, enabling efficient inter-VLAN communication and integration into a larger routed network.