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or more precisely: what websites perceive ones IP address to be?

I've always thought your IP would stay the same and changing your DNS would just effect how it resolved others Names to IPs but someone told me they switched to OpenDNS and that somehow changed what their IP was reporting as?

Just looking to clarify, thanks.

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What do you mean by "websites percieve ones ip address to be" your direct connection to the webserver does that. –  Ramhound Mar 6 '14 at 15:06
    
Ah someone was saying that by changing their DNS it could have done some tunnelling automatically and therefore it wouldn't be a direct connection to the webserver. Not sure how that would be possible though. –  Richy321 Mar 6 '14 at 17:29
    
@Richy321 I think Ramhound was referring to site such as google "my IP" function or "whatismyip.com" or similar –  Fazer87 Mar 7 '14 at 9:55

2 Answers 2

up vote 2 down vote accepted

Changing to using a different DNS provider will not change your IP address.

It is possible that if your IP has changed recently - some DNS servers have updated and know your new IP, but others haven't and don't - this process of "propogation" can take quite some time in some cases.

This could give off the impression that your IP has changed at the point of changeover.

Likewise, if you switched DNS servers and this involved rebooting a router or resetting your connection as part of the change process - a new IP may have been leased out by the ISP in question which would have actually changed the IP, but it still was not caused by the DNS server change.

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This was my understanding as well. If they have a static IP then it makes it even more unlikely right? –  Richy321 Mar 6 '14 at 14:12
    
It does make it more unlikely - in the same way that a reserved DHCP IP would also make it less likely, however, since a DNS server change cannot trigger an IP address change - this is the only real logical explanation i can fathom. –  Fazer87 Mar 6 '14 at 14:16

There's a lot of layers here that could be influencing what is perceived from different points of view, so...

Yes, it is entirely possible that changing the DNS server that you use for resolution changes your IP address on the receiving end.

The responses you get for IP addresses from Content Delivery Network (CDN)-based services can change because folks use Global Server Load Balancing (GSLB) tricks to route you to the closest web server in their "cloud" based on the IP address that asked their DNS for the website name. As an example, if you switch from your local ISP to use OpenDNS, the IP address that makes the final leg of the DNS resolution request changes, so it's entirely possible that the CDN GSLB DNS servers perceive your client to be in a different place geographically than when your ISP DNS server does that final resolution leg. This then means your web browser connects to a different IP address to open the HTTP connection, and that different network destination might route your IP address through a different Network Address Translator (NAT) box so now your IP address is NAT'd to a different public IP address and that's what the web server sees when HTTP transport is connected.

This is all very common these day.

If your address falls in 10/8, 172.16/12 or 196.168/16, then you must be NAT'd and this all applies.

If you have a static public IP address, then this may still be happening (I've seen it, and scratched my head since it doesn't make sense), but is much less likely.

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