VLAN running out of IP addresses

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Jul 28th, 2008
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Hello

We have a class B network which is subnetted with a class C mask. Our server VLAN is now running out of usable IP addresses. We'd usually add a secondary IP address to the VLAN interface but I've heard that this is “bad practice” . I've had a look at using a vlsm for this VLAN but all our servers IP configs are hard coded on the boxes and it would involve a fair bit of work. does anyone have any other methods/ideas to achieve this?

Thanks

Andy


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tdrais Mon, 07/28/2008 - 05:06
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Not sure why you do not just add a second server vlan.


If we look at your first option of change the subnet mask the question is why do they need to be in the same broadcast domain. Even if you went to the pain to change this would you see any performance gain for doing it. How much do the servers actually talk to each other. Even if they do talk to each other layer 3 no longer slows you down in a switch.


The secondary IP is mostly used because you do not know what device is plugged in where. Even though they are on the same vlan other than for some broadcast traffic they operate as though they are on separate vlans. The subnets never directly pass traffic to each other.


The only difference in putting in a separate vlan and using a secondary IP is that you must take the additional step of assigning ports to this new vlan. In a server environment I would hope you have good control of what gets plugged in where.


bauti1428 Mon, 07/28/2008 - 09:07
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In our server farm, we have separate vlans for each group of applications. We separated subnet for citrix, Domain Controllers, and applications. We did this so we have control on each vlans and know what protocols supposed to be in that VLAN. You can create another VLAN and then start moving the servers in that VLAN.

andrewswanson Tue, 07/29/2008 - 01:55
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thanks for the input guys - creating a second vlan does seem like the best option for the reasons listed. think i can sell this to our server admins..

cheers

andy

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