Please let me know if is scenario on picture possible. I don't know how to configure layer 3 switch over routed ports with trunk link which is connected to layer 2 switch.

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  • Could you please write configuration of L3 Switch here ? Commented Oct 18, 2015 at 13:20

3 Answers 3


In your sheme you need 3 trunk links (if there is only one physical connection between these switches):

  • switch 1 to switch 0
  • switch 0 to switch 2
  • switch 2 to L3SW

The routing between these subnets will be handled by the L3 switch. so if pc 0 wants to ping to pc 1:

PC0 > (gets it on his vlan 1 port) switch 1 (trunk) > switch 0 (trunk) > switch 2 (trunk) > L3SW (vlan1 > vlan2) (sends it out of its trunk port) > switch 2 (trunk) > switch 0 (trunk) > switch 1 (vlan2) > pc1


A trunk link is a switched link, not a routed link. The port would not be a routed port, just an ordinary switch trunk link.

What you need to do is to create a layer-3 virtual port for each VLAN coming in on the switched trunk port. Cisco calls these virtual interfaces, SVIs. The SVIs are the routed ports, not the physical ports.

Based on your diagram, you seem to want to create a router-on-a-stick. You can do this. The port on the layer-3 switch will be configured as a normal switch trunk port. Inside the layer-3 switch, you create an SVI for each VLAN on the trunk, and you configure it as you would a routed port (IP address, etc.).


In L3 switch After Configuring Switch virtual interfaces(SVIs) to route all traffic towards down stream switch vice versa .

In L3 switch

L3Switch(config)#int G0/1 L3Switch(config)#switchport mode trunk L3switch(config)#switchport trunk encapsulation dot1 q L3switch(config)#no shutdown

In switch2

L2(switch)#int G0/0 L(switch)#switchport mode trunk L2(switch)#switchport trunk Allowed vlan all L2(switch)#no shutdown

From L3switch to L2 switch ===> trunk link

From Switch2 to switch1 ====> trunk link

From switch0 to switch1 ===> trunk link

From Switch1 to PC0 & PC1 ===> access port allowing specific single Vlan ..

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