Request.UserHostAddress and IIS Logfiles

[cbanks]

I have read the messages about (not) always obtaining the 'actual' ip
address of the sender using Request.UserHostAddress. What I don't
understand is why does the W3SVC1 show one ip address and
Request.UserHostAddress another?

I have a table for active users which inserts the userid, ip address,
valid login and date/time. I was hoping to determine which user was in
what part of my application at a given time. By using
Request.UserHostAddress I thought I could create a relationship with
the logfile to identify the user.

If some one could explain to me why there is a difference I would
really appreciate if.

Thanks
Charles