Issues subnetting a wireless LAN 1

[ciscokidjt]

I'm looking for experienced feedback from someone who has deployed wireless on a semi-large LAN. There are three wings of our corporate office, and we have piloted Cisco wireless AP's in one of them successfully, and want to cover the rest of the building. The issue I have is that while it would be nice to have all wireless on one subnet (and thus avoid the problem of having people drop off the network when moving from their desk to a meeting in another wing / on another subnet), I'm concerned about network congestion. Could anyone tell me a)if it's possible to break the environment up into multiple subnets and allow connections to dynamically move w/o dropping packets, or b) if it's safe to have one big subnet with potentially 400 - 500 wireless users on it. ??

 

[bcastner]

It should not be a subnet issue.
Depending on the Cisco access point, it should be a controllable feature to adjust the wireless density, or transmission coverage of each access point. You want identical SSID, WEP or other encryption keys, and unique channels.

Cisco has a tool to essentially picture the AP coverage at your site. You want a "Ven Diagram" like picture with small overlapping areas of each circle.

 

[ciscokidjt]

Is Solution Engine the tool that you speak of? We are in the process of ordering that right now. So, what we can do is create a separate vlan for each wing, but allow for instances of all vlans on all AP's, correct? I'm also thinking we'll want to set up the solution engine first and see how good of a job we did coverage wise in the one wing that is finished before we continue.

 

[lui3]

don't go with a subnet larger than class c or 254 users. vlans can handle larger subnets but in most cases the performance really takes a hit due to excessive broadcasting etc. especially in windows environments. i would also segment the wireless users on one subnet and the wired users on another subnet and access list protect the wired subnet where you servers reside.

 

[bcastner]

ciscokidjt,

You are starting on the right step with your excellent questions. Lazy son of a gun that I am, as you are already commited to Cisco APs, let the Cisco folks analyze your existing site and future plans.

Call Cisco. They have a range of self-diagnostic and analysis tools, all free, and should offer without charge to you to send an engineer to analyze your existing site and recommend solutions for your expansion plans.

This is one of several things that Cisco does very well.

I would take all recommendations made by them with a reasonable dose of salt. You spend time with the Cisco engineer during the analysis phase. You do not want to overbuild the solution, but the roaming and VLAN issues you have raised are excellent questions that Cisco will answer for you if asked.

A site analysis is available for the asking. I always buy lunch for the Cisco engineer, smhooze them a bit, and ask for everything in writing. I think you will be pleasantly suprised as to how many of your concerns can be handled with a decent job on your part with the vendor.

I should note that HP and IBM offer equivalent level of free support for your plans; and likely others as well. This is not a time to be modest. Avail yourself of the esentially "free" or at modest cost engineering talent available from the vendors.

And for a specific problem, there is always Tek-Tips.

Best,
Bill Castner