iP Lease time

Anybody know why after several weeks of an IP change every couple of days, I've now had the current IP for 17 days?

Edited by hk11 (Mon 21-Oct-19 14:24:27)

Well I didn't know that, but I do now.

In reply to a post by RobertoS:

Well I didn't know that, but I do now.

I couldn't tell what the question was but re-reading it after your comment I do now - so I didn't know the OP had the same IP for the last 17 days either.

It is possible the OP might have been asking why it has been the same for 17 days when previously it had changed more often.

OP - if that was your question then generally IPs only change if the session is disconnected/reconnected. It is possible there were issues on your line or at the ISP that were causing some sort of regular reconnection and that whatever they were have now been largely resolved.

You lot are a scream! LOL

One missing word "why", now inserted.

Thanks Ian, but previous ISPs usually changed every few days as well; right through a twelve month contract. Only one I have known to have a "sticky" IP was Virgin Media.

Edited by hk11 (Mon 21-Oct-19 14:28:30)

Did my actual answer in my post make sense?

Yes, and might even be the "correct" answer, given that this is a new contract with a new ISP. Just seemed odd to me, given my previous experience.

I wondered if the shortage of IPv4 addresses meant fewer were getting back to the IP pool or some configuration at Talktalk meant Shell Energy were treated differently from other customers?

Edit:-

I know Sky and Plusnet have what they call DLM that changes an IP every 24 hrs untill the speed settles.

Edited by hk11 (Mon 21-Oct-19 14:36:51)

It is down to the ISP - changing ISP will change how it works. ISPs have been known to sticky assign addresses so they barely change at all - it is quite possible Shell will just keep giving you the same address or it may just be you haven't lost connection in the last 17 days and therefore it hasn't had to reassign the address.

There is no benefit to an ISP automatically disconnecting a customer to free up an IP because the router will connect back up in a matter of seconds anyway - so still using the same number of IPs. Shortage of address space is not what drives changes to IPs on your connection.

Shell energy may well be assigning addresses from their own IP pool rather than TalkTalk's - not sure how TalkTalk deal with IP on their wholesale network.

In reply to a post by hk11:

You lot are a scream! LOL

One missing word "why", now inserted.

I wasn't feeling very bright, so genuinely didn't realise what you meant to be asking. My post was in expectation of your clarifying things, as you have done .

No problem.

You manage to suss out far more than I would.

Obviously a case of *I* knew what I meant.

Yes, you would think that changing ISPs would change how it works, but, in my experience, it doesn't.

I eventually gave up waiting for the IP to change and swapped the router back to the one I have had for *five* ISPs now. We will see if my IP changes in a couple of days again or not.

No, I thought it was a pretty daft idea to blame IPV4, but sometimes these things do effect others were you might not think they would.

No, I am not familiar with Talktalk either. My IP always comes up as a Talktalk one anyway. I've never seen Shell Energy mentioned. In fact I think if anyone were mentioned it would be First Utility.

Are you wanting the IP to change?

No. I was waiting for it to change to swap the router over. It didn't really matter. Just interested to know why it became sticky after weeks of regular changes. Obviously disconnecting the supplied router dropped the connection and caused an IP change.

Interestingly I am now on an Opal Telecom DSL IP, but with soo many ISPs being bought out, you can't really tell a lot from the IP anymore. When I was last with Plusnet I suddenly started getting BT IPs. Obviously Plusnet were/are part of BT, but I think Plusnet did run out of "their own" IPs.

If you don't disconnect the session on a router then theoretically you could keep the address forever. As I said in my first response the address will only normally change if the session is disconnected - the fact yours changed every couple of days before suggests either their was a problem or the ISP was forcing session disconnects for some reason - in the past I have had times where I have had the same IP for months and that is perfectly normal.

I should add, IP lease time is not what you might think it is.

In a LAN the IP lease time is the minimum amount of time an IP would be assigned to the same device. However, periodically the device will go to the server to say "I'm still here, please extend my lease". There is nothing in LAN DHCP that would automatically force a device to get a new IP if the device was working correctly.

ISP IP address assignment works a little differently to LAN DHCP but in essence this is no different - the lease time does not affect how long a device will keep the same IP if it is permanently connected.

It's odd as my router has been on pretty much 24/7 for the last five years and apart from one year where I purchased a static IP as part of one of my Plusnet packages, my IP has changed fairly regularly.

Like I said earlier I am familiar with Sky and Plusnet DLM but not with Shell's system, if indeed there is one.

Yes, I am familiar with requests being, say half of the lease time.

Perhaps I should have titled my post ISP address assignment, but it doesn't have the same "ring" to it.

The comment still stands - lease time makes no difference unless the link disconnects at some level. As I say, what you are seeing is perfectly normal behaviour for a stable connection.

DLM is Dynamic Line Management and is a VDSL2 layer, i.e. nothing to do with the IP layer and also is run by Openreach for VDSL2 services. ISPs have some limited input but the variations are just the changing data meaning DLM behaves slightly differently.

I've a feeling it is the BT Wholesale DLM in question, or may be TalkTalk Business. AIUI the OP is on ADSLx via a Technicolor 582N.

Your comment is of course valid for that too.

I just assumed the DLM would cause the line to drop and hence a change in IP.

Still don't really understand it as I have now had three different IP addresses since changing the router.

New router solves the NAT loopback problem, but you answer would suggest it has caused the line to be unstable in some way?

Maybe the new router has caused the line to re-train or something?

Yep: Shell Energy BB via Technicolor TG582N as per my signature.

Router was supplied to me by New Call Telecom five years ago and worked fine with Plusnet, Sky and NowTV BB. Think I might have also used it with EE for a few months, but .....

Check the logs in the router to see if there are resync events or if the session is being disconnected. That might give a clue as to what is happening - maybe it is just an unstable router.

Can't see anything.

My point was the previous (TG588 supplied by Shell) router was the same for a few weeks. so I don't think it is a router issue.

It's all DHCP so it's all the same. Asking for a renewal of a lease can be denied by the server whether it is LAN or WAN. A disconnect can result in a change of IP address whether it is LAN or WAN.

It's all down to how the DHCP server is configured. I could easily make a LAN DHCP server look like one from an ISP because fundamentally they are highly likely to be the same piece of software.

It may not be a router issue but if there are logs that would help to see what is happening. Without logs it is guesswork. At the least does it tell you the uptime of the link and session? That would give an idea of whether the link is disconnecting - the question that would follow then is why but without logs we are probably going to have random chance to guess the answer to that question.

There are logs, but they contain nothing useful. e.g. :-

Jan 3 19:13:07 LOGIN User Administrator logged in on [HTTP] (from 192.168.1.67)


Info Jan 3 18:37:49 IDS fragment parser : fragment out-of-order (1 of 2) : 199.6.1.30 89.243.x.x 1492 UDP 53->11798 frag 23211:1472@0+


Info Jan 3 17:50:53 LOGIN User Administrator logged in on [HTTP] (from 192.168.1.67)


Warning Jan 3 17:50:38 IDS proto parser : tcp data on syn segment (1 of 1) : 192.168.1.67 17.252.11.246 0298 TCP 62869->443 [S.....] seq 2754500809 win 65535


Info Jan 3 16:28:44 IDS fragment parser : fragment out-of-order (1 of 6) : 149.20.64.3 89.243.x.x 1492 UDP 53->40479 frag 50761:1472@0+


Warning Jan 3 14:26:18 IDS proto parser : tcp data on syn segment (1 of 1) : 192.168.1.67 17.252.11.246 0298 TCP 61957->443 [S.....] seq 532413401 win 65535



Uptime: 1 day, 4:06:33

Does the uptime of 1 day, 4 h, 6m, 33s coincide with the last time the IP changed or has it changed more recently than that?

Good question.

Last (on Linux server) shows first log in with new IP as Tue Oct 22 13:49 - 13:50 (00:00)

Have to post this and look back at date and time my post with uptime was posted.

Edit: Wed 23-Oct-19 13:00:28.

So answer is 1 day 50 mins, looks about right.

Edited by hk11 (Wed 23-Oct-19 18:12:46)

It suggests the IP change is just a side effect of a resync. What you need to try and find out is why the line keeps resyncing - the fact it has started happening more on changing the router means either it is the router or changing the router has triggered something else (like DLM to become more active).

I suspect the later, but without knowing who triggers the DLM........

I think I just have to wait and see if this router "settles" as the other one did.