IP Number

On windows, open a dos prompt and type ipconfig. On unix based systems, it's ifconfig -- can't remember the arguments.

Easier:

http://www.whatismyip.com/

Oh, that's neat. I don't know if that works if you're on a subnet, though. Guess it depends on why you need to know...

Easy indeed! Thanks.

By the way, whatismyip.com will tell you your external IP address...which for most people is not the same as their internal LAN IP address.

If you need to find your internal IP addy on a Windows 9x box, click Start -> Run -> type: Winipcfg

On Windows NT/2K/XP, click Start -> Run -> type: Cmd -> type: Ipconfig

IP2 is a freeware, standalone app that'll find both at the same time.




Huh? What are you talking about?

The LAN IP.

Oops what gives? http://www.whatismyip.com/ gave me one IP number yesterday and a completely different one just now.

That's because you have apparently a Dial-up (modem) connection.

Cable and DSL connections can change as well, just not nearly so often (and they don't have to change, whereas it would be pretty rare for diall-up not to)

Yes I have dial up. So my IP changes all the time? I know of a forum manager who apparently keeps track of posters including those he bans by their IP number. How could that work if the number is constantly changing?

Good question!

It doesn't really work at all. Banning by IP address is unreliable. Very few people actually have static IP addresses. Every time you dial in, you'll get different modem, and each modem will have it's own IP address associated with it. It's unlikely to get the same number twice in a row. An ISP could easily have 20, 30, 50, 100+ lines. Cable and DLS connections can also change from time to time.

If my IP address gets banned, if I'm on dial-up all I have to do is hang up and redial and I should be able to get right back to where I was. Similarly, I could just issue a command to my cable modem or cycle the power, and it could nab a new IP as well. There is another way though. A range of IP addresses could be blocked. This could effectively block out an entire ISP. The user would have to switch ISP's in order to get around it, which is more bother than it's worth for most people. It's also worth noting that the dedicated individual could just spoof their IP address and get around the block as well. Ever tried to block spammers by their email address? It's the same type of thing. The forum software could probably be written in such a way to get around this to an extent, but most software isn't written with security in mind so it wouldn't surprise me if they weren't. What I mean by all of this is that I could write a program to just send the data to post a message and then put a fake IP address in the header. If the message board doesn't need to get a second confirmation from the user, then it will just post it and send the "your message has been posted" page to nowhere (the fake IP address). Of course the poster doesn't really care, because their message got posted anyways.

Of course there's a downside to all of this blocking as well. If an entire ISP is banned, suddenly no one from there can get access at all. This obviously isn't a desirable situation. Even if single IP addresses are blocked, an innocent user can have that address allocated to them and they will be blocked. This is why I say that IP blocking really doesn't work. It's OK for small sites (where the chances of someone else from the same ISP wanting to go there is slim (assuming you haven't decided to block out AOL... ), but for larger sites it would just be a nightmare. It could be "working" in that the user isn't likely to show back up, but then a lot of other people can't either.

On the other hand, I've never really been a forum manager, and for all I know they have some system worked out that gets around the limitations that I've mentioned.

Bookmark

Bookmark?

I just do that to bookmark the thread when I don't really have a response but want to keep track of it. Sorry. I know it bugs some people.

Oh, I didn't know. I thought maybe you were suggesting bookmarks as a way to effectively block people.....

LOL!

slaad-thank you, that was a great explanation.

I haven't quite been a forum manager, but I am a moderator on one and I've had other experience that's related (e.g. designing web servers) so maybe I can shed some light. Dynamic address assignment, as for dialup, is not the only problem with IP banning. The other problem is proxies. Anybody whose IP address has been banned can simply go to one of hundreds of public web proxies, and the address that the site sees will then be the proxy's rather than the actual users so they can get around the IP ban. This is also one of several reasons why going to a website to find your IP address doesn't always work and using ipconfig instead is recommended.

Some proxies include a special HTTP header in requests that they forward on behalf of users, identifying the real originator. The web server has to be prepared to look for this header, though, and many proxies very deliberately do not include this information. That's usually one of the things that makes an "anonymous" or "anonymizing" web proxy different than a regular one). Blocking an anonymous proxy would have the unfortunate side effect of blocking every user of that proxy, which is very similar to blocking every user of an ISP that uses dynamic address assignment.

There are a couple of other tricks that can be used to detect and foil proxy abusers, but I'm not going to talk about those. I'll just say that IP blocking and proxy detection are useful tools, but hardly foolproof. Some day we'll have to have strong end to end authentication so that sites can associate you with an identity (possibly a pseudonymous one to avoid problems with disclosing real identity) regardless of what path was taken from your desktop to their server. David Brin's Transparent Society has a good discussion of the non-technical (and very lightly technical) issues involved.