change subnetmask on controller

[Hubert Kupper]

Hello, I must change the subnetmask on the management interfaces of our controllers, because the IP range in the subnet reaches its limit. Our APs are configured with static IP adresses. Do they fall back to DHCP when I change the mask or must I change every AP to dhcp previous?

Regards, Hubert

[patoberli]

Neither should happen. But you should adjust the subnet mask on each AP afterwards for correct broadcast function. 

[Scott Fella]

Patoberli is right.  don't half a$$ it.  If you change anything for the management, come up with a plan to make changes to all devices using that subnet.  Seems like you are better off using dhcp and remove the static, then once you have everything up and running, then create the static if you want.  Mac address reservation I think would be better for you, just think everything through so you don't end up with a bunch of access points that no longer connect.

[Hubert Kupper]

The plan was to use dhcp for future instead of static IPs. I thought when change the subnetmask on all controllers and the dhcp server the APs will do a fallback to dhcp and join the controllers after the change. Am I right?

[Scott Fella]

The ap's fallback to dhcp when the ap can't discover the controller.  I would not count on that as that can cause you issues.  Take time and figure out what steps you need to take to reduce downtime.  

[patoberli · Accepted solution]

Yes, in a certain way. Only if the AP can't reach the WLC with the configured IP address it will switch to DHCP. You didn't write anything about changing the AP manager interface, so I expect the AP to not switch to DHCP.
I personally would first switch them all to DHCP (with option 43) and afterwards change the WLC interface configuration.

[Hubert Kupper]

Ok. Thanks for the answers. I will figure out a way with the least downtime.