BigIP persistence cookie changing in middle of session.

User goes to the login page, they will get the BIGIPServerPool cookie. Once they authenticate they will get the application cookie. As long as they keep on hitting the right server with the application cookie, everything will work fine. If they hit a different server with application cookie, it will result in Session Not Found/User not Authenticated error.

We are using Cookie persistence with default values (no expiration)

We set the following Cookie

Response sent 55 bytes of Cookie data: Set-Cookie: BIGipServerpool_app=3728940042.20480.0000; path=/

Then 4 or 5 requests later, the request now has

Request sent 95 bytes of Cookie data:

            BIGipServerpool_app=3594722314.20480.0000
            applicationcookie=bo5fhllsdbjgnmwstqroyp2j

I understand the additional application cookie but why did the BigIp cookie change? The session did not close and there is no expiration set.