Cisco 3750 Routing the interfaces on the same subnet

briangeorgevinson · ‎03-14-2007

Hello all,

Question is it possible for a Cisco 3570 to have two vlans with the same subnet and route in between them?

Example

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current topology

A flat LAN with a default gateway of 10.1.1.5 255.255.0.0. This gateway device is a firewall out to the internet.

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Addition of WAN line.

A WAN line via a 2811 router is now connected to the switch. which provides access to the 172.26.0.0 255.255.0.0 network.

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So I could I configure routing between three vlans with two of them being the same subnet

ankbhasi · ‎03-14-2007

Hi Brian,

It is not possible to have 2 different vlans with same subnet. If you try to assign the same you will be prompted with an error message saying "overlapping address".

On the reverse side you can have same vlan with different subnets using "secondary" keyword.

HTH

Ankur