Why do I have different IP addresses on different websites?

My wireless router shows the IP address is 113.46.75.*, which some websites like ip138.com, www.ip.cn show as my IP.

But other websites, like googling for "what is my ip", www.whatismyip.com, www.whatsmyip.org, show that my IP is 121.18.126.*.

I am very curious why this happens and how is it possible.

So, why do different websites show that I have different IPs?

Thanks all!

Plus: I changed my IP address several times (restarting the modem) and all addresses is like 113.46.*.*, but my IP address does not change when googling for "what is my ip".

My ISP is a small company, so I think it is true that when visiting some websites, I am NATted or proxied to some IP addresses which have access to those websites -- not to avoid firewall though, since I am still blocked from some websites.

But I still want some more information or resources to support our guess. Thank you!

saltycookie

Posted 2012-02-18T03:25:46.457

Reputation: 53

Do a traceroute to any website and watch how many times the ip changes, gives you an idea what NAT does....http://en.wikipedia.org/wiki/Traceroute

– Moab – 2012-02-18T04:38:56.430

Answers

Chances are that what you are seeing as this "wrong" IP address is a transparent proxy between you and your Internet service providers connection to the internet.

This is basically what paxdiablo was trying to get across, with NAT you don't necessarily get local addresses assigned and it is actually possible that you have a fully accessible "normal" IP address (so you can run servers and voip clients that require incoming connections) but your actual data connection is through a transparent proxy that catches and caches a good number of websites so that they can do things like caching common websites and reduce overall bandwidth used for those sites.

What this means is that depending on how the site resolves your IP or whether the transparent proxy kicked in your address may appear differently to the site that is trying to trace you.

I have found this a couple of times with my isps in the past. If you try to do a 'whois' lookup on this odd ip address then you may well find that it belongs to either your isp or their upstream provider.

An alternative is a 'hostname' lookup which may resolve to something useful like proxy.somelocation.myisp.com as it has done for me in the past when I have encountered this seemingly odd situation.

Mokubai

Posted 2012-02-18T03:25:46.457

Reputation: 64 434

Welcome to the wonderful world of NATting, firewalls, routers and other associated network infrastructure.

Your local IP address is rarely what the outside world sees you as simply because of NAT (network address translation).

Your ISP or local router will generally do this translation for you in such a way that many different people can share the same IP address (local ones like 10.x.x.x or 192.168.x.x, for example, and from memory so don't take the actual values as gospel). These local addresses are ... well ... local, so they don't get "published" to the real Internet.

That way, we didn't run out of IPv4 addresses back in 1986 :-)

user53528

Posted 2012-02-18T03:25:46.457

Reputation:

He is not talking about local IPs. He is talking about the external IPs that some pages are reporting. Your answer is all wrong. – zenw0lf – 2019-10-11T15:55:33.317

2113.46.75.* does not look like a local IP address, though. – Thilo – 2012-02-18T03:32:47.560

No, that may be the address assigned by the ISP. It's likely to have a bank of real addresses which it can use. Or it may be a misconfigured router :-) The possibilities are almost endless. – None – 2012-02-18T03:34:27.573

Reserved addresses are those in the ranges 10.x.x.x, 192.168.x.x and 172.16.x.x (thru 172.31.x.x). See http://en.wikipedia.org/wiki/IP_address#IPv4_private_addresses

– Kyle Trauberman – 2012-02-18T03:35:39.723

No, 113.46.75.* is not local. So my ISP assigns another ip address for me when visiting some websites and translate it back when receiving the response? seems complex. – saltycookie – 2012-02-18T03:43:41.793

It is complex. So complex that we don't actually know what your router/modem/ISP is doing :-) Your router may run it's own little mini-segment of local addresses but talk to the modem on a different segment. The modem may also talk to the ISP on a different range of IP addresses. And, seriously, what happens within and beyond the ISP is anyone's guess. – None – 2012-02-18T03:47:37.837

1Ummm. Local and global ips have nothing to do here. In both cases the websites are showing global ips. And those are not guess, they are well defined. – Bibhas – 2012-02-18T06:44:40.883

ip138.com, www.ip.cn appear to be Chinese, the other sites are not.

If you are also in China, then perhaps you are being proxied to sites outside of China to avoid government firewalls (or alike)?

Ƭᴇcʜιᴇ007

Posted 2012-02-18T03:25:46.457

Reputation: 103 763