Is Flexconnect really needed?

[akisbouza]

We are planning to deploy Wireless in our Branch offices (250). 

Each office will have a 32 Mbps line with the Central DC

Since currently in each branch office there is a need for only 1 SSID ( with Internet access from Central DC) is there really a necessity to implement Flexconnect?

I mean the traffic will be centrally switched and there is no need for local switching.

What are the pros and cons of not implementig Flexconnect in Branch Office Enviroment?

[Freerk Terpstra]

FlexConnect pros:
1) The ability to local off-load the client network traffic
2) Let the access-point perform the authentication itself while the connection with the controller is disconnected. If you use dot1X the access-points should still be able to reach (some) RADIUS servers, if those are also located somewhere within the WAN there is no benefit.
3) Clients will still be connected for as long as they are authenticated and not roaming during WAN problems.

Based on your situation I doubt if there are any benefits, except for having the possibility to easy implement local off-loading in the future. One exception I can think of is the use of the vWLC which requires the access-points to be in FlexConnect mode.

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[akisbouza]

Thank you very much for your answer.

I was also thinking that Flexconnect could be useful in the future if more SSID's will be added but currently i could not find any reasons to implement it.

We were thinking of using local DHCP (router)  for Access Points in each branch with DHCP Option 43 in order for them to find the controller and register.

About clients i was thinking that it would not be a good idea for WLC to handle the DHCP traffic for the clients in 250 branches (as it not designed for such operations) and i would like your opinion whether it is better to

1. Implement an external DHCP Server in our DC (and a backup in the Backup DC)
2. Implement local dhcp server (router) in each branch

Additionally any ideas for HA as we are buying a backup WLC operating in the backup DC

Regards

[Freerk Terpstra]

Local DHCP scopes on the WLC is not recommended, so I agree on your suggestion to centralize it. It does depend on your infrastructure, but why not define all of your DHCP scopes on the two central DHCP servers? With centrally switched WLANs the WLC will proxy DHCP so the clients will think that the WLC is their server. This helps for the renewing of leases when one of the two servers are down.

I would create a AP VLAN on every branch location and let the default-gateway (core switch or router) relay DHCP. If you are going to use local switching you need to do the same for the specific client VLANs and make sure that DHCP req. is actually disabled on the WLAN because the WLC does no long "see" the DHCP traffic in that scenario.

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