The O2/Be system is weird.

It seems to tie the IP address to the router. Changing router will change the IP address, and reverting to the first router normally reverts to the original address.

Edited by RobertoS (Thu 18-Aug-11 11:49:10)

If you cloned the MAC for the WAN interface it would probably be the same on the different router

NOTE:

Providers who do use dynamic IP's do keep records of who has which IP at what time.

Also dynamic's are why whole blocks of IP's are sometimes black holed by mail servers, i.e. avoids bots being blocked on IP and surfacing on a different IP in the same block.

In reply to a post by Andrue:

The fact someone has to actually ask if anyone knows of an ISP where the address changes suggests to me that most ISPs are running a pseudo static addressing. My own ISP - BeThere - definitely seems to. Back when I had a dynamic IP address I'd switch my router off before going on holiday. I'd come back over a week later and get exactly the same IP address.

BE, until recently, were unique in their use of IPoA, which more often than not seems to tie the customers IP address to the MAC address for long periods of time. Every other ISP (apart from more recently Sky) use PPPoA which in most cases is set up to offer "proper" dynamic IP addresses.

Edit: I was slow to click submit so RobertoS has already said it

Edited by Oliver341 (Thu 18-Aug-11 10:21:43)

In reply to a post by AEP:

It's difficult to think of valid reasons for dynamic addressing.

I assume in the dial-up days the IP would get re-allocated when the user shut down their PC. In those days less IPs could go round more users. Nowadays it's one IP (or more) per user.

It does provide a modicum of IP privacy from spammers for the user, but one would question why the user is attracting spammers.

In reply to a post by MrSaffron:

If you cloned the MAC for the WAN interface it would probably be the same on the different router

Correct! That has been demonstrated. That doesn't alter the fact it's a weird sort of dynamic address.

In reply to a post by Oliver341:

Edit: I was slow to click submit so RobertoS has already said it

But you explained it. I had no idea why it is like that.

As I've mentioned before, I think it's a shame that BT Infinity (consumer) has no static IP addressing option, when the increased upload capacity provides more opportunity for running servers. I don't think running servers is the preserve of "business usage" these days. I hope IPv6 means a shift to static addressing, but that's not necessarily a given.

LIkely to be only an option on the business products which is what BT Total does now for its ADSL/ADSL2+ range

Servers like slingbox usually have their own system for tracking access do dynamic is not an issue

But there are applications where static IP addresses are much more preferable, such as running a mail server. I don't think running a mail server is the sole preserve of businesses anymore, for privacy reasons an "in-home" mail server makes quite a lot of sense.