newbie_scoobie

I'm confused...

Col

Mr.Cookie

when your puter connects to a website it lets it know where it's from and what systems are running so web pages look right in browser for instance, all this does is mirror back the info you send out.

Si

ADP

plenty of these things all over the web, like http://www.whatismyipaddress.com

can be done easily with some Java Script for example http://simplythebest.net/scripts/javascript_118.html

chiark

Oh my god, you're giving out your IP address!

Turn your computer off immediately and disconnect from the net!!!!!

Nimbus

Except it's the wrong IP...

Fig

HTF can more than one person/router have the same IP address?

Fatman

It's quite normal for IPs to be non-unique. I believe it's something to do with sessions, although someone who works for an ISP (?) could probably answer better than I. It's something along the lines of an ISP having multiple sessions open per IP. It associated the connections to the session and the session to the username, rather than connections->username directly.

Fig

My office has had the same 'sticky' dynamic IP address for months. I can connect from home using PC anywhere by connecting to the IP : port.

If the ISP uses sessions as you say, how does it know which session to connect my incoming packet to?


Edit cos I didn't want an IPort



[Edited by Fig - 10/31/2003 4:17:40 PM]

chiark

NAT...

Fatman

Oh, OK... that makes sense. It's just like the way you share your office's single internet connection with your colleagues. Or, the way a family might share a single ADSL or cable line.

Fig

I understand how NAT works in the office/at home, but surely no two machines can have the same public IP address?

Fatman

Why not? It's the same principle, just scaled up. The only difference I can see is that in 'local' NAT envionments, non internet-routable addresses are allocated.

Fig

Agreed, but with non-internet addresses, you cannot have two PCs on the same network using 192.168.0.1 simultaneously. Therefore I would presume that you cannot have two users on the internet with the same public IP address simultaneously, especially not through the same ISP.

I thought maybe it was something to do with subnets, but my current IP is 81.86.xxx.xxx with subnet of 0.0.0.0

Fatman

We've exhausted my knowledge of IPS mechanics! Any Scoobynetters work for an ISP?

Gedi

I don't work for an ISP, but I am cisco certified and work as a security admin with CISSP etc.... Hope that qualifies....hehe

no 2 users can have the same IP address. As Chiark says, NAT, proxy's etc handle your internet requests.

e.g. 3 users behind NAT have the following addresses:
192.168.0.2
192.168.0.3
192.168.0.4

The gateway running nat has 192.168.0.1 on the LAN, and 666.666.666.666 for its WAN address.
If any of these 3 computers make a request, a packet will be sent with their address (192....) to the gateway. The NAT software will collect the packet, strip it of its IP and replace it with its own WAN IP and send it on its way.
It will cache what machine requested the info and when the packet returns the the NAT gateway, it will again strip the destination IP from the packet and replace it with the initial 192.16.... IP

Thus, if any of these 3 computers request information from the net, they will all appear to have the same IP, the IP of the gateway running NAT.

This is the reason people in the copmuter industry hate AOL so much. They run this method behind proxies. If you ban one AOL user from using your services, you ban many many more.

[Edited by Gedi - 10/31/2003 6:05:51 PM]

Fig

Gedi,

Yes, I understand all of that, as I said above. The question was could two PCs/users have identical PUBLIC IP addresses. The answer is obviously no.