We are currently running a pair of 5508wlc with a third 5508 as an anchor for guest access. We are replacing them with 5520. However, can we replace the existing 5508 with an HA pair of 5520 and still use the existing 5508wlc as the anchor, or do the models all need to match? What about software? Does that need to be the same version as well, or just a version that supports anchoring?
I ask because we are currently using the 5508 anchor with internal DHCP for the guest and public subnets and the 5520 does not support internal DHCP. We would like to swap out the main 5508wlc for the 5520HA pair until we figure out the route we are going to take for the guest/public wifi DHCP... (from the ASA, or internal DHCP server, etc....)
Keeping 5508 as a Anchor and 5520 as a foreign WLC will work without any issues.
Since 5508 is a anchor IP address will be provisioned by that. So that clients will get IP from 5508, which is anchor .
regarding the version, you have to run both the controllers on a recommended code as suggested by Cisco.
I understand they need to run a supported/recommended code, but does the code have to match between the foreign and anchor WLCs?
Nope. Refer Compatibility Matrix