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Since I changed my ISP, I have had issues logging into sites (e.g. StackExchange), MMORPGs and connecting to SMTP servers. I did some research and it turns out that my public IP address is changing constantly (in a matter of minutes at most). I get my private IP address via DHCP but so far it's using the same IP address consistently.

On StackExchange I get the error message that my client is behaving suspiciously and therefore login is not possible. In MMORPGs I get a message while loading the game that the IP address has changed since logging in. In Thunderbird emails are downloaded from the server but cannot be sent since the connected to the SMTP server is not possible. I have tested it with two different SMTP servers.

Is there a way to remedy this? As far as I know just using NAT shouldn't cause any issues. Is the rapid change of the public IP address what actually leads to the response from the SMTP to be lost on the way back to my client? Would a WLAN router be any help at all?

Tested on Win7 and Linux Mint 16.

Thank you in advance for any advice and pointers in the right direction.

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up vote 1 down vote accepted

It seems that the problem you are facing, is in most cases a "security" feature - at least in the sense that many websites and applications will log you out if your IP-address changes after logging on. Thus, one login with associated cookies will only be usable with the same IP-adddress.

The best part to remedy this is to make sure you do not have such a rapidly changing IP-address. A much more common dynamic IP-address would in many default server environments be at least 8 days, but this is surely something that is dependant on your ISP - not your own setup locally, provided you have a router.

I personally recommend you contact your ISP if you have a configuration-less-modem, that they configure centrally, so that you can get further information on how often it is meant to change.

Anecdote: where I live, it is much more common for ISPs to give you a new IP-address upon every reconnection. In which case, is your connection stable?

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