do ISPs keep track of end-user IP changes within thier network?

Staudinger, Malcolm mstaudinger at
Fri Dec 13 22:55:10 UTC 2013

I'd say in addition to just "how long", it's "how badly do you need them ". Searchable database could go back a few months while tapes usually exist for a lot longer than that. But you're not going to get the provider to dig through those unless they're under some legal obligation to do so. 


-----Original Message-----
From: Ray Wong [mailto:rayw at] 
Sent: Thursday, December 12, 2013 12:50 AM
To: Mikael Abrahamsson
Cc: nanog at
Subject: Re: do ISPs keep track of end-user IP changes within thier network?

been a while, but seems like lately it's more a question of how long. ISPs can be in position where they need to, but as things have consolidated, seems like they'd really like to forget it as soon as they can. If you've got a specific case in mind, likely best to find a direct contact and get a response about policy, even if it has to be off-record. The big ones (like one I likely shouldn't mention by name unless they do as I don't work for
them) definitely do, at least long enough to handle DMCA requests and other legal obligations.


On Wed, Dec 11, 2013 at 9:36 PM, Mikael Abrahamsson <swmike at>wrote:

> On Wed, 11 Dec 2013, Carlos Kamtha wrote:
>  just a general curiousity question. it's been a long time since ive
>> worked at an ISP.
>> back then it was non-expiring DHCP leases and in some cases static IP 
>> for all.. (yes it was long ago..)
>> Any feedback would be greatly appreciated..
> Yes, it's very common to keep track of what user account/line had what 
> IP at what time.
> --
> Mikael Abrahamsson    email: swmike at

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