Knowing the different Cisco LAP modes.
It’s been a while since my last wireless post, and surprisingly I never done a post regarding the different modes a Cisco LAP can operate in. I figured this would be a great place to start up my wireless posts again!
Now depending on the model access point you are working with and which IOS you are running you may or may not be able to operate a LAP in all the modes I will be describing:
Local: Probably the most common and well-known mode a LAP operates in mainly because this is the default mode a LAP will operate in (Unless you are running Flex controllers). In local mode, the LAP maintains a CAPWAP (or LWAPP depending on your IOS version) tunnel to its associated controller. All client traffic is centrally switched by the controller which why LAPs have been referred to as ‘dumb’ APs, primarily due to the fact it does very little thinking on its own. As a matter of fact, if a LAP operating in local mode loses its connection to the WLC, the LAP will stop forwarding and begin looking for the controller. Until the LAP (operating in local mode) joins another WLC it will not forward any user traffic.
REAP/H-REAP/Flexconnect: This mode has certainly evolved over the years and certainly deserves multiple posts of its own. REAP stands for Remote Edge lightweight Access Point and is there to address the scalability issues with Local mode after all it is completely unfeasible to place a WLC at every branch location. If you had every LAP operating in Local mode and you experienced a WAN failure at the location housing your WLC, every LAP in your network would stop forwarding user traffic, crippling your wireless networks. LAPs operating in REAP mode do not always require a connection to the WLC, and have the capability to locally switch WLAN traffic without relying on the controller. The functionality of REAP was later expanded to H-REAP (Hybrid-REAP) getting a littler better with each code release. Later on H-REAP was later re-branded again being called Flexconnect gaining a host of new features.
Bridge: Bridge modes have been around a long time, and as you would expect allows you to bridge together the WLAN and the wired infrastructure together.
SE-Connect: SE-Connect mode allows you to connect to the LAP using Cisco Spectrum Expert and gather vital information about the RF spectrum surrounding the LAP. Do keep in mind a LAP operating in SE-Connect mode will not be broadcasting an SSID and does service any WLAN clients. This mode is strictly used for troubleshooting purposes.
Sniffer: Similar to SE-Connect mode, a LAP operating in Sniffer mode is strictly for troubleshooting purposes. Sniffer mode will passively monitor the surrounding WLAN environment (Over a specifically configured channel) and tunnels all the 802.11 WLAN traffic to an end point on your network (configured by you), where you can use protocol analysis tool (Wireshark, Airopeek, etc) to review the packets and diagnose issues.
Rouge Detector: Again similar to SE-Connect & Sniffer mode, Rouge Detector mode does not service any WLAN clients. Rouge Detector mode connects to your wired infrastructure usually over a trunk link and watches the traffic traversing the VLANs. The LAP in Rouge Detector mode is watching for any MAC addresses that other LAPs have marked as a wireless ‘rouge’ device. Think of this as a tag team match up, your LAPs operating in Local or H-REAP/REAP/Flexconnect modes are passively watching and reporting rouge APs and rouge WLAN clients, while the LAP in Rouge Detector mode is watching the wired network for the MAC addresses of those same rouge APs and rouge WLAN clients. It’s there to be an extra layer of security in the event your users connect rouge APs, you use a Rouge Detector LAP detect and alert on those events.
Configuring the AP mode can be from the CLI of the WLC using the following command: config ap mode %AP Mode% %AP Name%