'Reserved' IP & New Router WTF?

'Reserved' IP & New Router WTF?
Links: home · search · speed test · login · more ·

Links: Reply New Topic
Forums » Canadian » Cogeco » 'Reserved' IP & New Router WTF?
page: 1 · 2
rickardsred @ 15th Oct 03:02PM:
'Reserved' IP & New Router WTF?

Here's a question for the Cogeco DHCP experts...

I have a client who has a business account with a 'reserved' IP that they've been using for years. They wanted to upgrade to a new router since their old one has been acting flaky for awhile. I setup the new router and figured I would just clone the WAN MAC addy off the old one, swap it in and be done.

So I go onsite, drop in the new router, tell it to renew the DHCP lease and - Yoink! Different IP....not the reserved one! WTF?

Okay....verify that the MAC is correct, release, renew....Yoink! Same IP....not the reserved one! WTF?

Put the old router back....Voila! - Correct IP....Hmmmmm

Put the new router in, this time set it back to factory default WAN MAC address. Release, renew....okay different IP than before, so obviously the DHCP server is seeing the different MAC address and offering up a new lease. Ok....release IP, change WAN MAC back to the one on the old router. Reset, renew IP - Yoink - same IP I got in step 1 - not the reserved IP again?

I can't understand why the DHCP server isn't offering up the reservation to the new router if it appears to have the correct MAC address. The only thing I can think of is that the new router is asking for a new lease, and the server already has an existing lease for the same IP. Unfortunately, the old router doesn't have an option to release its WAN DHCP lease, so I might be out of luck until it expires on its own?

Didnt' have time to dick around with it, so I hardcoded the IP/SubnetMask/gateway into the new router and left it with the cloned MAC. Everything's working for now and I figure I'll wait a few days and see if once the original DHCP lease expires, I can set the new router with the cloned MAC back to DHCP and see if I get the correct IP?

Any toughts?
reply

Asawulf @ 15th Oct 03:55PM:
Re: 'Reserved' IP & New Router WTF?

The thing to do is like you are setup now; ie enter the Reserved IP settings manually...

Are you sure the customer pays for a Reserved IP ?

And why use/dabble with DHCP if your customer pays for a Reserved IP ? The very nature of DHCP is against a Reserved IP :S
reply

rickardsred @ 15th Oct 04:23PM:
Re: 'Reserved' IP & New Router WTF?

I guess my question then is if I leave the WAN IP settings set as static in the router, will it come back to bite me later on?

I would think Cogeco would frown on that no?

Perhaps as long as the IP is still reserved in the DHCP server and the MAC address matches the reservation it should continue to work unless Cogeco reallocates DHCP ranges at some point in the future?

Just to note...the customer does indeed have a 'reserved IP' as opposed to a 'static ip'. It's been like that for years. The original IP in question is bound to the MAC address of the old router they had when it was first configured - I remember calling in with the MAC and having them add the reservation. It's just that the new device with the same MAC doesn't want to pull this IP via DHCP.

At one time, that was the only option Cogeco had for business clients that wanted a non-changing IP. I know I can call in and get them switched to a true static and they'll come down and drop in a cisco router with /30 on it. I may end up doing that eventually anyway.

I was just hoping a simple router swap wouldn't turn into an ordeal of having to change IP, and the associated annoyance of having to make dns changes etc. This was originally supposed to be a quick job....but we all know that quick jobs don't really exist in the real world? ;)
reply

TimCampbell @ 15th Oct 05:36PM:
Re: 'Reserved' IP & New Router WTF?

Call in and have them change the reservation to the new MAC and you're all set. New router will pull old IP from DHCP server.
reply

rickardsred @ 15th Oct 06:22PM:
Re: 'Reserved' IP & New Router WTF?

Yeah....the problem with calling in the new MAC is that they don't change it immediately for you. The business CSR usually has to escalate it to someone higher up and in the past I've had it take up to a week to get a DHCP reservation straightened out.

In the mean time, the customer is in limbo if they're hosting anything locally that relies on that IP like a mail server. Not too bad if they have the ability to change their own DNS records easily, but still a pain nonetheless.
reply

TimCampbell @ 15th Oct 06:38PM:
Re: 'Reserved' IP & New Router WTF?

When my reserved IP was changed due to my node changing, they had the DHCP admins on the phone with the tech support person and fixed my IP while I was waiting. Sometimes you get lucky.
reply

Marcer @ 15th Oct 07:06PM:
Re: 'Reserved' IP & New Router WTF?

said by rickardsred :

I guess my question then is if I leave the WAN IP settings set as static in the router, will it come back to bite me later on?

Since the router is set static, it won't make any attempt to renew, the DHCP lease will expire and then you will have problems. Best to have this addressed sooner rather than later, when your client can no longer surf.

said by rickardsred :

I would think Cogeco would frown on that no?

Personally, I would frown on it, as it is not a best practice to statically route within a dynamic scope.

I would believe that due to the manner in which traffic flows across the network, and that once the lease expires, the router on our end would stop passing the traffic to the modem, it would not be a great concern, as there is no impact to our network.
reply

Asawulf @ 15th Oct 09:53PM:
Re: 'Reserved' IP & New Router WTF?

My apologies, I got confused since Cogeco Quebec doesn't offer Reserved IPs as in Ontario (we only offer dynamic or static...) so in my head you were using the word "reserved" to speak of static :huh:

So I got mixed up :( That's what happens when you read too quickly for your 1 hour of gotten sleep brain... I forgot about the choice offered in Ontario...
reply

nevertheless @ 15th Oct 10:14PM:
Re: 'Reserved' IP & New Router WTF?

said by rickardsred :

So I go onsite, drop in the new router, tell it to renew the DHCP lease and - Yoink! Different IP....not the reserved one! WTF?

Okay....verify that the MAC is correct, release, renew....Yoink! Same IP....not the reserved one! WTF?

People often assume that the MAC address is the only factor involved in a reserved IP, but there's more to it than that--with Cogeco's DHCP server the client ID is usually taken into account when processing a lease and is quite often different from dhcp client to dhcp client--you can't just clone the MAC and expect it to work (for those paying attention, that's why you sometimes get different IPs when dual-booting using the same hardware.)

So, basically, fudging the same MAC information and expecting the lease to move to your new hardware is generally not a good idea and should certainly be done AFTER talking with commercial support as well as being in a planned outage window.

Cogeco now offers and has offered a static product for some time and I'd suggest you look into that product if the above conditions exist and you're making hardware changes--I'm not on the billing side of things but I do not believe the cost is any different.
--
Some people think I'm an idiot. I disagree, but idiocy is subjective--so they may well be right. With this in mind, take everything I post with a grain of salt, eh?
reply

AMailer @ 15th Oct 10:22PM:
Re: 'Reserved' IP & New Router WTF?

Doesn't cogeco offer you the ability to change the MAC address at MyCogeco?
reply

rickardsred @ 16th Oct 08:48AM:
Re: 'Reserved' IP & New Router WTF?

said by nevertheless :

So, basically, fudging the same MAC information and expecting the lease to move to your new hardware is generally not a good idea and should certainly be done AFTER talking with commercial support as well as being in a planned outage window.

I figured there must be more going on behind the scenes, thanks for the info! I'm going to recommend they switch over to a true static anyway.

The whole ordeal with switching hardware with a reserved DHCP address is something I've actually come across a few times now. I've always been curious as to the technical reasons why it sometimes works and sometimes doesn't, but never really had the time to investigate it.

Thanks for the info :)
reply

nevertheless @ 16th Oct 08:58AM:
Re: 'Reserved' IP & New Router WTF?

said by rickardsred :

Thanks for the info :)

No problem.

I've never been happy with this 'reserved IP' system. It's called the 'Dynamic Host Configuration Protocol' for a reason and should be left that way.
--
Some people think I'm an idiot. I disagree, but idiocy is subjective--so they may well be right. With this in mind, take everything I post with a grain of salt, eh?
reply

nitzguy @ 16th Oct 09:43AM:
Re: 'Reserved' IP & New Router WTF?

said by nevertheless :

said by rickardsred :

Thanks for the info :)

No problem.

I've never been happy with this 'reserved IP' system. It's called the 'Dynamic Host Configuration Protocol' for a reason and should be left that way.

Yes, but it makes configuring printers that aren't going to move around much easier vs. setting that printer statically up and then creating the associated routing for those 500 printers that I have to deal with :).

That's the pro to "reserved IP". It probably works better in a business workplace environment vs. a large scale MDU HFC environment :).
reply

Snickerdo @ 18th Oct 11:28AM:
Re: 'Reserved' IP & New Router WTF?

said by nitzguy :

That's the pro to "reserved IP". It probably works better in a business workplace environment vs. a large scale MDU HFC environment :).

That's exactly it. Throw that MAC address of each printer into the DHCP server and assign it a reserved IP and just let them pick up the same address off DHCP each and every time, rather than running around and configuring each and every one of them manually for a static address.

I use a lot of reserved IP, if only for ease of administration.
--
Give a man a hooker and he'll have fun for a night. Teach a man how to hire a hooker and he'll have fun for a lifetime.
reply

rickardsred @ 18th Oct 01:09PM:
Re: 'Reserved' IP & New Router WTF?

said by Snickerdo :

That's exactly it. Throw that MAC address of each printer into the DHCP server and assign it a reserved IP and just let them pick up the same address off DHCP each and every time, rather than running around and configuring each and every one of them manually for a static address.

I use a lot of reserved IP, if only for ease of administration.

I use it for the odd client PC as well....mostly for people who VPN in from home and want to be able to RDP into their office workstation.

If I had the time to really dig into this, I'd love to put a hub in between the modem and the router, then plug in a laptop and do some packet captures of the DHCP process to see what information is actually being sent back and forth.

Since simply cloning the MAC didn't work, it would be interesting to compare the results with the two different routers to see what the differences are.
reply

Snickerdo @ 18th Oct 06:04PM:
Re: 'Reserved' IP & New Router WTF?

said by rickardsred :

I use it for the odd client PC as well....mostly for people who VPN in from home and want to be able to RDP into their office workstation.

Bah, that's what host names are for ;)
--
Give a man a hooker and he'll have fun for a night. Teach a man how to hire a hooker and he'll have fun for a lifetime.
reply

nitzguy @ 18th Oct 07:50PM:
Re: 'Reserved' IP & New Router WTF?

said by Snickerdo :

said by nitzguy :

That's the pro to "reserved IP". It probably works better in a business workplace environment vs. a large scale MDU HFC environment :).

We've got some real clunker HP Laserjet 4's and Laserjet 5's and some other old HP Printers...DHCP and go...trying to put in a manual IP on those things is...god awful to say the least.

Probably why we went with reserved IP in the first place. Also, subnets aren't changing that often with my company with current moves and whatnot there is lots of address space available.

...I'm not primarily responsible for our VPN but, I connect with the Cisco VPN client and...everything is win :).

That's Costa Rica's job to handle VPN ;).
reply

Snickerdo @ 18th Oct 08:41PM:
Re: 'Reserved' IP & New Router WTF?

Yeah our guys connect using the Cisco VPN client too. Once they VPN in, they then use the RDP client to log into their machine at the office. They always use their host names, though sometimes we've found that they have to use their FQDN for it to work. I had one situation where they had to use an IP, but that was only once and if it ever changes they can just get a hold of me and I'll get them their new one.
--
Give a man a hooker and he'll have fun for a night. Teach a man how to hire a hooker and he'll have fun for a lifetime.
reply

rickardsred @ 19th Oct 02:41PM:
Re: 'Reserved' IP & New Router WTF?

Just to follow up....after a couple days with IP address hard coded into the router they lost connectivity, which I assume coincided with the original DHCP lease expiration. I went back and flipped the new router back to DHCP with the cloned MAC address and it worked fine. Picked up the proper reserved IP and all is well.
reply

nevertheless @ 19th Oct 03:26PM:
Re: 'Reserved' IP & New Router WTF?

said by rickardsred :

Just to follow up....after a couple days with IP address hard coded into the router they lost connectivity, which I assume coincided with the original DHCP lease expiration. I went back and flipped the new router back to DHCP with the cloned MAC address and it worked fine. Picked up the proper reserved IP and all is well.

As expected. :)
--
Some people think I'm an idiot. I disagree, but idiocy is subjective--so they may well be right. With this in mind, take everything I post with a grain of salt, eh?
reply

Marcer @ 20th Oct 01:01PM:
Re: 'Reserved' IP & New Router WTF?

said by Marcer :

Since the router is set static, it won't make any attempt to renew, the DHCP lease will expire and then you will have problems. Best to have this addressed sooner rather than later, when your client can no longer surf.

Hey... is there an echo in here?
reply