Hi Jay,
Yes, with software version 7.4.x onwards you can used 2504 as guest anchor. Here is a Release note on 7.4 which is listed this feature availability.
Guest anchor on WLC 2500 | Provides the ability for 2500 Series Wireless Controller to act as the guest anchor. | Customers can now use 2504 as guest anchor, which can support up to 15 EoIP tunnels. |
HTH
Rasika
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