can we assign same subnet IP on same switch SVI and OOB Interface

[hashimwajid1]

Hi,

I've single subnet 10.10.10.0/24 and I want to assign IP to Catalyst 9300 dedicated OOB Management and In-Band SVI from same subnet.

SVI IP = 10.10.10.1

Dedicated OOB IP = 10.10.10.2

both IPs will configured on same switch but in different VRF. my question will it create any conflict or any issue in future??? or is it achievable?

[M02@rt37 · Accepted solution]

Hello @hashimwajid1 

Thanks to VRF, yes, you can assign 2 IP from the same subnet to diferent interfaces on the same switch without a local conflict. Since each VRF has its own routing and ARP tables....

However, for devices "outside" the switch, you must carefully manage routing _ each VRF’s IP is only reachable via its own gateway, so reusing the same subnet can cause asymmetric routing or confusion.

For sure, the best approach is to keep OoB trafic on a separate subnet.

[David Ruess]

M02@rt37 Is right and so are you. With the VRF it will not create a conflict as each VRF to include the global one maintains a separate routing table independent of each other. It doesn’t even have to be a different IP. The same IP can be used. You would just have to set it up where you can access both the global network and the VRF network.

-David

[Joseph W. Doherty]

As the others have already described, yes, using different VRFs you can have overlapping IP usage between different VRFs.

However, does doing this guarantee no issues, especially future issues?  Well, no, because it's up to you to avoid overlapping IP usage in the same L3 topology.  Although each VFR device has separate L3 information, it's possible to "leak" L3 information between VRFs and a non-VRF device could incorrectly join VRFs.

So, the important question, should you overlap IP address space?  I.e., just because you can, should you?

The correct answer is an "it depends".

[Giuseppe Larosa]

Hello @hashimwajid1 ,

it is technically possible, but on the long term assigning a dedicated IP subnet to the OOB management provides a clear design and it avoids any possible confusion anywhere.

Thanks to the use of dedicated VRFs it is easier to choice a new subnet.

Hope to help

Giuseppe