Aironet Controller-based infrastructure deployment with redundancy

[cluca_alex]

Hello community!

I have, as a project, the below infrastructure. The client wants that his employees who travel from one city to another, to connect to their corporation's wireless automatically, without any other settings needed, on the same SSID. He also wants WLC redundancy, so that when one WLC fails, the other one, across the VPN, would function instead, taking under his wing the orphan AP's. Both networks have dedicated DHCP and DNS. Both networks can ping each other through VPN. The things that is confusing me, after thinking of a possible configuration setup is related to DHCP. I know that AP's make DHCP requests through a dedicated UDP port, making broadcasts that only WLC's understand. The WLC then asks a DHCP for one IP for the AP. When that WLC fails, DHCP fails too. So, if the AP turns to the backup WLC and let's say, it will reset itself and then he will need to renew his IP, it will receive an IP from another network. Is this correct? Because the other WLC will broadcast for DHCP IP in his network, and will receive an IP from his network, forwarding it to the orphan AP who is in another network. Is this logical from the Cisco appliances point of view or not? Will this infrastructure function like described?

Looking forward for your response,

Thank you!

[Rasika Nayanajith · Accepted solution]

Yes, this is possible

So, if the AP turns to the backup WLC and let's say, it will reset itself and then he will need to renew his IP, it will receive an IP from another network. Is this correct?

Yes, that's correct.

Refer this post to see how DHCP works in typical network environment. By default WLC act as proxy for DHCP request of wireless clients.

https://mrncciew.com/2012/12/27/understanding-dhcp/

HTH

Rasika

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[cluca_alex]

I have tested this in a little lab configured just like in the image above, and all works like a charm and strangely enough is that the orphan AP's takes refuge on the backup controller but with an DHCP IP assigned from their network. I don't understand how it works exactly. Maybe the backup controller tells the orphan AP to make a usual DHCP request to it's network and after it is assigned with a valid IP, to contact him again and establish the CAPWAP tunnel.