Non Registered IP address Used by Member

[gabs007]

Greetings.

Today I saw a user logged in, I know he is using multiple accounts So I wanted to know more about him.
I clicked on the option "see the full users list" using the admin account on the index page and the Block "who's online" and I could copy the ip. He was logged in with 1 specific IP.

Then I logged in the Admin CP and used the option: Members - IP address Tools and pasted the IP in IP Address Lookup.
I got 0 results and according to the block, that user had been logged in.

Could someone highlight me a little more about this issue ?
Thank you

[gabs007]

Nothing ? 

The index page says the user is logged in with one specific IP and when I check the IP in the admin CP that IP has not been saved; it's not there . Moreover, according the last IPs used by the user, last IP used was a month ago but "last visit" from the user says it was a few hours ago.   
It's complicated to check user "misbehaviour" with this uneven data.

So the user logged in but the system did not save his IP.  
Any thoughts ?