How To Connect Layer 3 Switch To Router?

The Cisco switch has Enhanced Multilayer Image (EMI) feature that enables it to work as a Layer 3 switch. Read the following procedure to connect Layer 3 switch to the router.

  • Step 1 :Activate routing on the switch by running the following command.

IP Routing

  • Step 1 :To check if routing has been activated on the switch, run the show running-config command. If IP routing has been enabled, you could see the ‘ip routing’ command in the list.
  • Step 2 :In order to route between the VLANs, make a note of them. Here, let’s make use of VLAN 1, 2, & 3.
  • Step 3 :Before proceeding, input the below command lines and verify that the VLANs exist in the VLAN database.

Show Vlan

  • Step 1 :If the VLANs are not present, use the below commands to create the VLANs. This will helps to connect layer 3 switch to router.
    • vlan database
    • vlan 1
    • vlan 2
    • vlan 3
    • exit
  • Step 2 :Know that the switch must route between the VLANs, so the VLAN must have an IP address. Assign an IP address to all the VLAN interfaces on the switch. The switch reads the routing table whenever the switch receives a data packet that is directed to any of the VLANs. It sends the data to the destined VLAN interface and then routes to the port of the connected device.
  • Step 3 :Use the following command lines to assign an IP address to the VLAN’s interface.
    • configure terminal
    • interface vlan1
    • ip address 10.0.0.2 255.255.255.0
    • no shutdown
  • Step 4 :Make use of the above commands to configure the IP address to the remaining VLANs.
  • Step 5 :Following that, configure the default router’s interface. It will be a vital part to connect layer 3 switch to router. Here, it is Layer 3 FastEthernet port.
    • interface FastEthernet 0/1
    • no switchport
    • ip address 10.0.0.10 255.255.255.0
    • no shutdown
  • Step 6 :The ‘no switchport’ command makes the interface Layer 3 ready.
  • Step 7 :Configure the switch’s default route with the below command. In the command, 10.0.0.1 is the IP address if the default gateway.
    • ip route 0.0.0.0 0.0.0.0 10.0.0.1
  • Step 8 :In case the switch receives a data packet for a network that is not present in the routing table, it sends the data to the default gateway. Check if you can send data from the switch to the default router.
  • Step 9 :Next, connect all the end devices as the default gateway to the VLAN interface of the switch (Catalyst 3550). Make sure the VLAN1 uses the interface VLAN1 IP address as the default gateway. You can also isolate VLANs when you are routing within the VLANs.
  • Step 10 :Enter the following command line to check if the configuration is working.

Show IP Route

  • Step 1 :View the entries of the VLAN interface subnet and the default route from the switch to the gateway. A summary of the IP details of the interface will help you understand the status. If you need remote assistance to connect layer 3 switch to router, contact our technical experts.