Size Of VLANS

[cecil.jackson]

I have 5 locations, each location has 50 3550 and about 10 3750 swithes. All are set up as layer two, We have core switch 6513 doing the routing. Each locations has about 1200 devices connected to these switches. I want to segment thes into multi vlans. Currently only 2 active vlans per site. Should I segment with /24 per to switches (design core6513> 3750 > 3550.

We are seeing alot of broadcast traffic. Most We have about 30 severs per location. Applications use TCP.

What would be a good design?

[glen.grant]

Wow that is a lot per subnet . Yes usuing /24 should work well for you , we use this in a large corporate environment and have never once had a problem with any kind of utilization problems on the lan . Breaking up your current environment should improve the performance , like you said there have to be a lot of broadcast traffic with 1200 users . I would say 5 -6 vlans (subnets) per site should do the trick and give you a stable enviroment . Do all your homwork as far as spanning tree goes such as making sure the 6513 is the root for the vlans . Avoid daisy chaining if possible. Obviously swithstacks like the 3750's are fine . Might want to put the servers on their own vlans and if possible feed that vlan with a gigabit feed or ether channel a couple of gigs to the switch that feeds the servers ..

[cecil.jackson]

thanks

[vladrac-ccna]

you should follow cisco recommendation of 1 vlan per subnet, and I'd suggest using /24 subnets per vlan, but it really depends on your site and the location of the servers. For wireless usually /24 is too small.

Check these links for a start:

Internetworking Design Basics

http://www.cisco.com/univercd/cc/td/doc/cisintwk/idg4/nd2002.htm#wp3380

http://www.cisco.com/univercd/cc/td/doc/cisintwk/idg4/nd2012.htm#wp3662

Vlad