Session Hijacking? X-Forwarded-For, different between Login and subsequent request

See more:

ASP.NET

PHP

session

When user login into the web application, I capture 3 values and stored it in session state:

IP 
UserAgent 
http-X-Forwarded-For

During login, http-x-forwarded-for has empty value. The log file shows that, the http-x-forwarded-for has a new value when user assessing the home page, something like 10.0.0.45 or 10.0.0.51.

What could this means?

Should I end the session? or just load an empty page to the client?
Is this some sort of hijacking?