Router and L3 switch: vlan communication

Unanswered Question
Aug 26th, 2009


Im confuse. Lets say I have a L3 switch with vlan configured. Do I still need a router if I want different vlans to communicate. Though I have already network layer device, L3 switch.

Can anyone elaborate this. thanks

I have this problem too.
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yagnesh_tel Wed, 08/26/2009 - 18:20

You don't require router for vlan communication if you have layer 3 switch. Layer-3 switch will take care of routing between VLANs provided that you create SVI interfaces for each of those VLANs on switch.

yongsikahn Wed, 08/26/2009 - 18:24

no,, I think you don't need to use Router.

because the L3 can be supported routing.

so, if you want to put ip in the interface or you want to make a new vlan for access other vlan, you need to configure at the below.

first, Go to interface or VLAN interface

second, enter no switchport

third, give the IP address

fourth, i think you need Static routing or some other routing protocol method go other Vlan.


Jon Marshall Wed, 08/26/2009 - 21:47


You do not need a router to route between your vlans in this case. What you do is create L3 SVIs (Switched Virtual Interfaces) for each vlan.

So assuming you have 3 vlans on the switch -

vlan 10

vlan 11

vlan 12

switch(config)# int vlan 10

switch(config-if)# ip address

switch(config)# int vlan 11

switch(config-if)# ip address

switch(config)# int vlan 12

switch(config-if)# ip address

once you have created the interfaces as above then your vlans should be able to communicate.

Note that you do not need any static routes or dynamic routing on the switch because all the L3 interfaces are seen as directly connected. If you wanted to connect to another L3 device then you would need static/dynamic routing to exchange routes.

Note also you may have to enable routing on the L3 switch ie.

switch(config)# ip routing



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