Moving aside from the normal areas of routing and switching that I usually deal with, this post is about some recent wireless work I did. I was working with a Cisco vWLC for a proof of concept I was putting together. I quickly realized upon starting to do my configuration that the only mode supported on a vWLC is FlexConnect, so I started looking into this mode. I started looking at this because my access points would associate fine with the controller but none of my wlans were working. After research, this turned out to be because my APs were not in FlexConnect mode. Easy enough.
There are two main switching modes that this post will cover. Those modes are central and local switching. First you want to set the mode of the access point to FlexConnect as the mode. Then on the wlan, you have options to change between the switching modes: central and local. Those two modes and specifically how they relate to vlan access and dhcp is what I will focus on here. This option and a few other FlexConnect ones are shown in the image above.
FlexConnect Switching : Central
FlexConnect central switching is a mode that relies on the vWLC for switching and more importantly for my proof of concept, DHCP running on that vlan \ wlan. Central switching sends the traffic back to the vWLC and pulls the common options such as vlan assignment and (more importantly in my case) dhcp settings. This allows the access points to work very similar to a standard access point in local mode. In the case of my test, the clients connected to my access points at my remote locations were all receiving IP addresses tunneled back to the vWLC and the assigned vlan, etc from that wlan.
FlexConnect Switching : Local
FlexConnect local mode somewhat ignores the vlan and dhcp settings from the vWLC. My clients were dropped on to the same vlan as the access point running in FlexConnect mode with local switching. For my proof of concept, this would prove especially useful in cases where I wanted clients at a remote location to receive a local IP to that site instead of one tunneled back from the main site through the vWLC. They would look for a dhcp address like any local wired client would at that point. This would allow me to keep management easy utilizing the vWLC, but keep clients segregated at each location.
Easy Way to Remember?
I remember it by asking in my head: where am I going to get my IP address? Local switching gives me an IP on the local network (vlan) where my access point is running. Central switching gives me an IP address from my central network, specifically where my vWLC resides and by the options it dictates.
Now don’t get me wrong, there is more that you can do with FlexConnect, but I wanted to outline specifically the switching modes and how they relate to vlan access and dhcp, etc that goes with that vlan. This came in handy for this wireless project I was working on concerning in multiple remote locations, connected by vpn tunnels, all with access points connecting back to a central controller. This info proved valuable to me in this case, so hopefully it can help you as well!