Xtra broadband dhcp?

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kama

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Topic # 111410 2-Nov-2012 10:05

I've noticed today that when I reboot my modem I get the same IP. Power off does not help. For various reasons about every week I reboot it for a new IP. Are others getting this - is this the new standard?

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Hawkes Bay
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Reply # 710873 2-Nov-2012 10:27

I don't know about Xtra specifically, but DHCP doesn't necessarily mean your IP will change.

Read up on DHCP lease times etc.

It's possible (though pure speculation) that they are extending lease times out to make reporting by IP a little more legible (possibly re: Skynet), or simply that they have plenty of IPv4 and aren't needing to snaffle IPs for the next connection.

Assume with DHCP that upon any connection you could get a new IP, but a DHCP server can be set to hand the same one out under a few different circumstances.

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Talkiet

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Reply # 710875 2-Nov-2012 10:36

For various reasons, (mostly boring operational reasons to do with efficient content delivery and performance), IP addresses are very 'sticky'. That is, they will look and behave a lot like static IP addresses but you can't actually RELY on them not changing.

As far as your DSL router is concerned, the public IP address is being assigned by the PPP negotiation.

Regards
Neil G

NonprayingMantis

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Reply # 710879 2-Nov-2012 10:40

I think you need to power off and leave it for a few hours to reset your IP.

I note it sometimes just randomly resets every so often (seemingly no pattern as far as I can see - but it stops my unblock-us from working until I re-authenticate)

kama

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Reply # 710880 2-Nov-2012 10:40

Previously I was getting a different IP from Xtra on every modem reboot, or line reconnect, without fail. True, dhcp servers and/or clients can have preferred IPs.

tonyhughes

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Reply # 710888 2-Nov-2012 10:50

This is all normal behaviour for DHCP.

Unless you run the DHCP server (you dont, Xtra do), then like Talkiet says, you can never rely on getting a new IP address, just like you can never rely on keeping it either.

Dynamic effectively means the server will change it at will to suit its own needs (or instructions).

Plenty of free dynamic dns services around, or conversely if looking for dynamic specifically, you should really look at why you do, and address the cause instead of the problem (i.e. have better security, use a proxy, stop nuking your school etc).

kama

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Reply # 710904 2-Nov-2012 11:14

@Mantis: good idea, I'll turn the modem off overnight, see what happens. Thanks.

plambrechtsen

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Reply # 710913 2-Nov-2012 11:45

I can say with a reasonable assurance that it won't matter how long you leave your modem off. For the foreseeable future you are going to have a static IP Address due to as Neil said a whole raft of reasons internally. And for the conspiracy folks it's nothing related to the recent law changes.

This may change in the future to going back to a purely dynamic IP address, but for the moment the majority of customers would have a pseudo static address.

ghettomaster

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Reply # 710943 2-Nov-2012 12:36

Hi,

Something I have never understood about DSL connections is the need for dynamic IP addresses.

Sure in the days of dial-up you needed less IP addresses than you had subscribers for the same reason that you needed less phone lines - your entire subscriber base was never online at the same time.

However, with DSL, I would imagine 99% of subscribers would be leaving their DSL modems turned on 24/7, and subsequently requiring an IP address 24/7. I would have also thought that of those remaining 1% you would most likely be getting most of them online simultaneously at peak times.

Following this logic, I would have thought ISPs therefore need to own 1 IP address per broadband subscriber, or perhaps 99.5 per 100 which makes having dynamic IP addresses just to reduce your ownership of IP blocks by 0.5% seem too marginal to bother.

Following this logic even further, it makes charging a monthly fee for a static IP ridiculous as well because even if you are saving a marginal number of IP addresses, the type of user that is requesting a static IP is probably also the type of user that will leave their modem on 24/7 and require an IP from your pool 100% of the time anyway.

Anyway the reason I am raising this is because it seems some people from Xtra are participating in this thread and it would be nice to hear from the horses mouth why dynamic IP addresses are so common in ISPs. Most importantly is my logic above an inaccurate assumption? Is it a case that no more that 80% - 90% of DSL connections are ever online at the same time? I don't need to know the statistics if they are considered commercially sensitive but some sort of indicator that this is the reason, or perhaps that there is another reason, would be nice to know.

Regards,
GM.

Talkiet

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Reply # 710947 2-Nov-2012 12:47

Hi GM...

You're pretty close with most points...

It's not quite 99%, but it's a huge proportion of DSL users that are connected at any given time and yes, it increases in the peak hours. (There are people out there that turn off their ADSL routers when they aren't using the Internet)

Many Telecom plans include a static IP at no charge on request. Historical charging was to do with the management of these different addresses, not a strict resource cost.

Dynamic IPs are easy to configure but as content delivery networks become more critical to performance it's really important to know where your customers are, so a centralised pool of dynamic IP addresses for the whole country is a Bad Idea.

Smaller pools by geographic region are a Better Idea, and it just so happens that to make things easier, making the IP addresses sticky, since there's pretty much a 1:1 relationship between customers and IP addresses anyway.

Cheers - N

Zeon

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Reply # 710951 2-Nov-2012 12:49

Having a static IP would be nicer as you could then rely on it.

Talkiet

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Reply # 710952 2-Nov-2012 12:51

Zeon: Having a static IP would be nicer as you could then rely on it.

The vast majority of people don't need a static IP, or even know what one is. As I mentioned, many plans have a free static available so those that do need them can usually get them.

Cheers - N

ghettomaster

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Reply # 710988 2-Nov-2012 14:23

N - thanks for your reply. Good to know I wasn't too far off base. I had also wondered if it was simply to make management easier which it sounds like it is.

Now if you don't mind taking the time to divulge a little further there is something else I am trying to undersdtand. We had a customer where they had two DSL connections with the same ISP (Either Xtra or TelstraClear - I can't remember) - one in Auckland and one in Wellington - and they had configured both of their DSL routers to use the same username and password (don't ask me why). This worked fine until they requested a static IP address, at which point they started to have connectivity problems at both sites until we configured one of the routers to use another username and password.

What I struggle to get my head around is how the connection in Auckland managed to even work with an IP address that was intended for a Wellington connection. Obviously all DSL connections are not treated as one big LAN within the realm of their ISP due to the large amount MAC addresses, routing issues and security issues. Can you please give me an idea of what sort of routing arrangements are typically in place that would allow an IP to swap between cities so effortlessly?

Regards,
GM.

sbiddle

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Reply # 710995 2-Nov-2012 14:33

A username and password isn't required on Telecom connections because they use port based authentication. You can enter anything you want and it will work. A username and password is required (or at least was 18 months or so ago when I last dealt with an issue relating to this) if you wish to have a static IP, so clearly two connections with the same details would cause problems.

There are other ISP's also using port based authentication also.

Talkiet

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Reply # 710996 2-Nov-2012 14:33

ghettomaster: N - thanks for your reply. Good to know I wasn't too far off base. I had also wondered if it was simply to make management easier which it sounds like it is.

Now if you don't mind taking the time to divulge a little further there is something else I am trying to undersdtand. We had a customer where they had two DSL connections with the same ISP (Either Xtra or TelstraClear - I can't remember) - one in Auckland and one in Wellington - and they had configured both of their DSL routers to use the same username and password (don't ask me why). This worked fine until they requested a static IP address, at which point they started to have connectivity problems at both sites until we configured one of the routers to use another username and password.

What I struggle to get my head around is how the connection in Auckland managed to even work with an IP address that was intended for a Wellington connection. Obviously all DSL connections are not treated as one big LAN within the realm of their ISP due to the large amount MAC addresses, routing issues and security issues. Can you please give me an idea of what sort of routing arrangements are typically in place that would allow an IP to swap between cities so effortlessly?

Regards,
GM.

I can see exactly what would have happened there...

Typically users don't need to have the correct username/password in their routers and usually in fact, this is better since most of the attributes are set based on the port ID they present (which is not changable by users). Most users use a generic username (I think user@xtrabb.co.nz is one that works and is a default in some of our routers)

However there were a couple of attributes that DID rely on the correct username/password. They were port 25 unblocking and Static IP allocation. Note that these are changing to being port based auth as well gradually across the whole customer base.

So before a static IP was assigned, the users both connected and both got a dynamic IP address and everything worked fine.

When a static IP got assigned to the username, and then the company decided to have two routers both tell the network they were one person - the system got confused and that caused the issue. As I'm sure you discovered once the duplicate username/password was removed from one of the routers, the issue went away immediately.

Static IP addresses used to be a special case and would work anywhere that someone presented the right username/password (but this wouldn't redirect billing etc). This is gradually changing though.

Takeaway messages?

1) Using a generic username/password is fine in most cases
2) If you have port 25 unblocking/Static IP, use your assigned unique username/password (although it may not be needed it's not a bad idea to do this anyway)
3) NEVER let anyone else user your username/password, even if it's the same company.

Cheers - N

plambrechtsen

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Reply # 710997 2-Nov-2012 14:35

sbiddle: A username and password isn't required on Telecom connections because they use port based authentication. You can enter anything you want and it will work. A username and password is required (or at least was 18 months or so ago when I last dealt with an issue relating to this) if you wish to have a static IP, so clearly two connections with the same details would cause problems.

There are other ISP's also using port based authentication also.

If you are on the port based authentication, then it's all based off the port. You can put random strings into username & password and you will always get the same IP (if you're static or dynamic aka pseudo static). The old network you needed a username & password for static, but all customers are being migrated away from that stack.

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