Cisco Wireless Network Architectures

Lessons Discussion
41

Hello Laz.

Thanks, that makes sense!

I have a question regarding WLAN design.

Where is a WLC generally placed? I understand that this differs if you have a centralized or a distributed architecture but I just need a basic idea.

I often see it placed at the core layer which I suppose makes sense if you have several distribution layers connected to it. That way, each distribution switch is somewhat equally far away from it.

cisco-wireless-deployment-unified-wlc
cisco-wireless-deployment-unified-wlc2124×1672 293 KB

I guess it also makes sense if your user traffic is mostly from down to up, to a data center or to the internet since the core layer would be the closest to those resources. The configuration here is pretty simple and you can even configure a HA pair with another WLC.

But then again, if you have several remote sites and branches, having everything sent to your core layer, maybe even over a WAN link might not always be the most efficient method, so that’s where you could use a distributed architecture and have each site or a distribution layer have its own WLC. Another reason that I can think of here to use the distributed architecture is if you have way too many APs to the point where one or two WLCs don’t support them.

It seems like a lot to consider, to be honest. If your remote site has, say 2 APs, you don’t even need to add a WLC to it, you could just configure those two APs to run in FlexConnect instead.

Thank you!
David

42

Hello David

As I read your post, there really isn’t much for me to comment on. I agree with your logic. The number and placement of WLCs does depend upon multiple factors including the number of expected clients, the number of sites, the size of each site, where each site comes in contact with the Internet, and what kind of traffic your clients will be generating (i.e. primarily north-south in most cases, although some applications may require east west).

So based on this, you could have the following scenarios:

  • If you have one huge building, your WLC will best be placed near the core as in the diagram, with an HA arrangement with multiple WLCs,
  • If the scale is large enough, you may want to place WLCs at the distribution layer, to serve only the access layer below that section of the network, depending upon your expected traffic patterns
  • For multi site, if the sites are large enough, you’d want a WLC at each site. If not, then using FlexConnect would be preferable.

So yes, there is a lot to consider, especially at scale.

I hope this has been helpful!

Laz