Wireless Infrastructure Analysis: Local Mode Vs Flex Connect

 Today I will talk about the Wireless deployment modes and will discuss which and why to use that deployment mode in the your wireless network. 

Wireless Deployment :Local Mode
In local mode, an AP creates two CAPWAP tunnels to the WLC.  One is for management, the other is data traffic.  This behaviour is known as "centrally switched" because the data traffic is switched(bridged) from the AP to the controller where it is then routed by some routing device.

Locally switched means the traffic is terminated at the local switch adjacent to the access point. 

Fig 1.1- Wireless Local Mode

Its a good idea if you have traffic that the client is sending to the local site rather than it going via the controller and travelling over the WAN link twice say for file or print services

Wireless Deployment : Flex Mode
Flex Connect also known as HREAP by the old timers, allows data traffic to be switched locally and not go back to the controller.  It basically causes the AP to behave like an autonomous AP, but be managed by the WLC.  In this mode, the AP can still function even if it looses connection with the controller. 

Fig 1.2- Wireless Flex Mode

Also, anytime you want to switch traffic locally, that would be the time to use Flex Connect.  I used it once when my users were needing the wireless and wired networks to be on the same subnet for broadcasting reasons.

Limitations of Flex Mode

  1. With the deployment of the Flex Connect, it can supports up to four fragmented packets or a minimum 500-byte maximum transmission unit (MTU) WAN link.
  2. Here I am taking the example of the Cisco Wireless devices, Flex Connect is supported only on the following access points: Cisco Aironet 1130AG, 1140, 1240, 1250, 1260, AP801, AP802 and Cisco Aironet 600 Series Access Points.
  3. Clients that are centrally authenticated are re-authenticated.
  4. Client connections are restored only for locally switched clients that are in the RUN state when the access point moves from standalone mode to connected mode. After the access point moves from the standalone mode to the connected mode, the access point’s radio is also reset. 
  5. There is no deployment restriction on the number of Flex Connect access points per location. However, the minimum bandwidth restriction remains 128 kbps with the roundtrip latency no greater than 300 ms and the maximum transmission unit (MTU) no smaller than 500 bytes.
  6. Flex Connect access points support a 1-1 network address translation (NAT) configuration. They also support port address translation (PAT) for all features except true multicast. Multicast is supported across NAT boundaries when configured using the Unicast option. Flex Connect access points also support a many-to-one NAT/PAT boundary, except when you want true multicast to operate for all centrally switched WLANs.
  7. Flex Connect access points do not support client load balancing.
  8. Flex Connect supports IPv6 clients by bridging the traffic to local VLAN, similar to the IPv4 operation. Flex Connect supports client mobility for a group of up to 50 Access Points.
  9. Flex Connect does not support IPv6 ACLs, neighbor discovery caching, and DHCPv6 snooping of IPv6 NDP packets.

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