Different subnet masks in the Same vlan

Unanswered Question
Jan 28th, 2009

Hi

I am moving a company's network ip address range from 192.168.1.x/22 to 192.168.1.x/24

(Other VLANS will also be created)

My question is: in the VLAN where now all users and servers exists, i want to start changing manually the Subnet mask of the servers from /22 to /24.

Would it cause any connectivity problem with the remaining users that still has the subnet mask /22?

I have this problem too.
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mahmoodmkl Wed, 01/28/2009 - 13:57

Hi

u can use the other's ip subnet under the same svi but it needs to be as a secondry address.

Thanks

Mahmood

jorjes1984 Wed, 01/28/2009 - 23:22

Where do u mean the secondary address should be?

i didn't understood well what u mean

Joseph W. Doherty Thu, 01/29/2009 - 05:19

As Mahmood notes, you might be able to define a secondary address (which supports more than one subnet on the same VLAN). However, I'm concerned about the fact you would have overlapping subnets.

I assume you're hoping just to migrate subnet masks. However, moving from /22 to /24, you could have /22 hosts sitting on /24 network or broadcast addresses.

I would suggest moving hosts to a /24 that doesn't overlap with the existing /22.

e.g.

gateway device

interface someEthernet #

ip address 192.168.1.1 255.255.252.0

ip address 192.168.4.1 255.255.255.0 secondary

When you've migrated, remove the /22. At that point you could either make the new /24 the primary, or migrate to another /24 within the original /22 address block.

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