From this link(http://www.cisco.com/en/US/products/ps6366/products_tech_note09186a0080b1a506.shtml), I can see.
Mobility ping over EoIP—This test runs over EoIP - IP port 97 and tests the mobility data traffic over the management interface.
Note: Only one mobility ping test per controller can be run at a given time.
If there is a firewall present, make sure that the UDP port 16666 and IP port 97 are opened for communication between the WLCs.
My Question is, IP port 97 means TCP port 97 or UDP port 97, or both? I captured the communication between the Anchor controller and non-anchor controller, I couldn't see any packet with TCP or UDP port 97. Perhaps it's encrypted by LWAPP.
Any input will be appreciated.
Mobility data traffic is carried via Ethernet over IP (EoIP) which is IP protocol 97. This is the IP protocol number, not a TCP/UDP port value.
Your firewall rules should allow IP protocol 97 traffic between your WLCs. For some background reading on EoIP, please see RFC3378:
Hope this helps!