# of servers per vlan?

[james.hughes]

Hi - i'm building a new enterprise network. A 6509 at the distribution layer with stacked 3750E's on the floors. A pair of 6509's at the core.

Question: I'm segretating my servers into logical VLANS. How many servers per vlan is the optimum? My CCNP instructor guessed at 30, but didn't know.

Ideas?

Thanks.

[royalblues]

How many servers are you planning to deploy?

I would probably use a single VLAN for all the servers unless it is a very large number

Narayan

[james.hughes]

Hi

No, i can't do that. We're a small investment bank, with 600+ servers.

[Jon Marshall]

Hi James

Rather than use numbers it would be better to base it on applications / user access eg.

you may decide you want to firewall all your database servers. So it would make sense to have these on the same vlan.

You may decide that you want to load balance a certain set of web servers. They don't need to be on the same vlan but it would help.

If you base it on dept/application/security requirements it makes for a better network design.

HTH

Jon

[james.hughes]

Thanks Jon,

I will be doing the above, but insome cases it can run into a fairly large number. I should have phrased my question better, but after i have segregated by dept / app / sec, how many is too many in a single broadcast domain?

Thanks, James.

[Jon Marshall]

James

It's difficult to say because a lot depends on your server apps, the amount of broadcasts etc.

In our datacentre we do not go above /25's for server vlans but to be honest i wish we had gone for smaller vlans. Not because of broadcast issues etc. as they perform quite adequately but we are looking to migrate to new data centres and having to move /25 vlans at a time is going to be a pain.

HTH

Jon

[jwdoherty]

Something else you might want to consider is whether you desire to span VLANs across multiple switch stacks. If your doing routing on the distribution 6500s, and with the speed of L3 on 6500s, you might keep VLANs unique to each stack.

Whether to have multiple VLANs per stack is also influenced by whether you intend to route within the stack.