# DHCP problem with Charter modems...



## heat2thefire (Dec 12, 2008)

Hi all. I'm a Charter tech in TN and i'm trying to get some info to help out quite alot of customers that seem to been having the same issues. This is nothing that my higher-ups are willing to assist with because it seems that it is a customer issue. I have went to school over computer repair and I hate not being able to tell the customer what exactly is wrong. Here goes... What we are seeing is that the pc in question is locking into a standard public address- 169.254.-.-. No matter what we try, it still remains the same. We have removed the modem from the accounts and reprovisioned them (reset them up on the customer's account) and still the same. If we hook up a different computer to the modem it will come up fine. This issue is that it lacks the gateway and dns numbers to connect to the net. I have even gone as far as reinstalling the nic cards and reinstalling windows. I'm pretty stumped on what to do next because this seems to be happening more and more often and I really want to help instead of telling them it's not Charter's problem. Any help would be great.

Thanks, 
Chris


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## johnwill (Sep 26, 2002)

If you have done a total reinstall, and the connection and the cable have been tested with other computers, I'd have to start suspecting the NIC. OTOH, if this is happening to a lot of computers, there's no telling what it might be and if it's a common issue, or each of the instances is unique. There are many reasons for this to happen.

Next time it happens, try one of these repairs on the system in question, here's one for XP and Vista.


*TCP/IP stack repair options for use with Windows XP with SP2/SP3.*

*S*tart, *R*un, *CMD* to open a command prompt:

In the command prompt window that opens, type type the following commands:

_Note: Type only the text in bold for the following commands._

Reset TCP/IP stack to installation defaults, type: *netsh int ip reset reset.log*

Reset WINSOCK entries to installation defaults, type: *netsh winsock reset catalog*

Reboot the machine.






*TCP/IP stack repair options for use with Windows Vista.*

Start, Programs\Accessories and *right click* on Command Prompt, select "*Run as Administrator*" to open a command prompt.

In the command prompt window that opens, type type the following commands:

Reset WINSOCK entries to installation defaults: *netsh winsock reset catalog*

Reset IPv4 TCP/IP stack to installation defaults. *netsh int ipv4 reset reset.log*

Reset IPv6 TCP/IP stack to installation defaults. *netsh int ipv6 reset reset.log*

Reboot the machine.


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## heat2thefire (Dec 12, 2008)

I tried the one for xp and nothing worked software wise. I replaced the nic and bam...working again. Definately seems like a hardware problem but I had the same thing happen to me about a year and half ago and I fixed it by a total system wipe and reinstall. It happened on two laptops but didn't affect my desktop. I figured that it was some sort of malicious software that was on both laptops. I still have certain customers out there that are having the same issues and Charter doesn't want the techs touching the computers do to replacement if something goes wrong... I can't help but at least try to help them. Thanks for the help and please update the thread if you guys find out anything new to the issue. It just doesn't make sense for so many computers to start being affected by this issue.


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## johnwill (Sep 26, 2002)

Well, in the absence of any "hands-on" experience with the specific machine, I have to take each situation individually when I'm here. Even a subtle symptom may be significant in these cases, it's hard to evaluate from this end of the wire. :smile:


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## heat2thefire (Dec 12, 2008)

Alright. I'm back again with pretty much the same issues. I'm seeing this more and more in my area of operations and my company just doesn't seem to either care or understand the issue. I can understand it if it was just a pc every month or so, but it's getting to be where it's two a week. I have fixed most by changing out the nic card but I ran into one that did it straight out of the box. The Dell system was no more than a day old. I'm starting to think that there could be a server that is kicking these mac addresses out. My reason for thinking this is that when I install a new nic, there is a new mac address that goes along with it. The same goes with our modems and such. Is there anything server wise that would confirm this? I plan i escalating this issue up my chain of command but with Charter we all know how that works. Any help would be great.

Thanks,
Chris


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## johnwill (Sep 26, 2002)

It could be a switch that is somehow filling up it's MAC address table and won't let a new machine on. Have you tried power cycling the switches between the machine and the server?


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## heat2thefire (Dec 12, 2008)

I don't have access to the higher level stuff such as the head-end equipment and servers. Pretty much the only option besides getting some extra info online is to escalate the issue higher up the chain and hope that someone actually cares info to check into it. I just don't see how the system is able to kick these mac addresses off the system like it's doing. I understand that when I switch out the nic card that it changes the mac address and so, so I believe it's on that level or maybe something that I'm not seeing. I dunno to be honest at this point... I'm pretty well out of options.


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## johnwill (Sep 26, 2002)

Well, someone higher in the food chain is going to have to do some tracing to see what is causing the MAC address to be blocked. Have you taken these machines (or at least the NICs) to a different location and/or network and tested to see if they work there?


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## heat2thefire (Dec 12, 2008)

I myself have not due to the fact that it is not mine nor Charter equipment. I have talked to a pc repair tech that has hooked it up in a different area and has said that it works. I'm considering of taking a router with me to test if it is truly the mac address that is the problem. I had another one today with the same issue. I installed a new nic in it and still 169.254... I really don't get it at this point. If it is really a mac issue then a new nic would have solved that. If it is a software issue within the machine, then who knows. I realize that new and more complicated viruses come out everyday but this would be a stretch to be honest. I do know that the service is working within our modems due to the fact that I hook up a test laptop and get on the net. How would a server actually have control over the mac addresses anyways? I get that we setup everything through a mac address in the modem but how would it stop the network device's mac to stop. Any ideas? Thanks again for all the help!

Chris


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## johnwill (Sep 26, 2002)

Without knowing a lot more about the actual network, it's hard to even speculate on what is happening here. It sure seems to be an infrastructure control issue, and not a hardware issue.


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## heat2thefire (Dec 12, 2008)

I have to agree with you there. I'm seeing it not only within the desktops and some laptops, but also with our usb wireless adapters. It's definitely an annoying to the techs and our customers that this has become such a problem. I'm gonna turn in my log of jobs that have the same issues with them to my superiors and see what happens. I will keep you all updated when I hear more. Of course if you guys find out more info feel free to let us know. Thanks for all the help.

Chris


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## johnwill (Sep 26, 2002)

Sorry we couldn't get to the bottom of this one, but it appears this is a "hands on" type of situation.


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## pata19 (Dec 23, 2009)

I have a feeling Micros*%t may something to do with this. From what I found, this may be a problem with Vista computers and some computers that have xp and have updated to SP2or 3. Basically, the dhcp client cannot receive a dhcp address from certain routers and/or servers. Here is an article on the dhcp problem in Vista:

http://support.microsoft.com/kb/928233/en-us


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## etoft (Feb 9, 2010)

Hey heat...

I'm one of those Charter highspeed customers in Middle TN. I have a router between me and the cable modem (CM). When the router's DHCP lease times out, it often has problems getting renewing. I am not sure what the heck is happening, but IMHO it is most definitely on the Charter end. I bought a new CM...same problem. A new router...same problem. Connect computer direct to CM...same problem.

Recycling the CM and router *usually* clears the issue, but then when the DHCP lease times out...same problem. I'm sure this is a real HEADACHE for you guys in the field. You need to get the IT/Server guys involved...it is THEIR problem.

Also, every time I call tech support about it...the problem magically disappears before they can see anything. Not blaming the tech support guys though. I suspect that something they are doing as they set up to look at my connection is kicking the DHCP server in the **** and making it respond correctly.

I hope you can find the right guys to talk to. This is annoying, and expensive...I probably bought a new CM and router for no reason.


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## etoft (Feb 9, 2010)

Check out the following from a forum post back in 2003 http://lists.rlug.org/pipermail/rlug/2003-July/001920.html

I'll have to do some testing when I get home tonight.

On Sun, 2003-06-29 at 20:43, Ryan Finnie wrote:
> (Warning, long rant ahead)
> 
> This weekend I dropped SBC and got Charter net access. Turns out my
> apartment was not on the line assigned to me, which warranted a service
> call to get it working, but that is outside the scope of this discussion.
> 
> I currently use a Linksys WRT54G as my border router, which worked fine
> with SBC. But when I plugged it into the cable modem, it would not get an
> IP address. So I plugged my linux laptop in and ran dhcpcd, again,
> nothing. However, when I plugged in my Windows box, it would get an IP
> address. Then unplugging the windows box, plugging in the linksys, and
> cloning the windows box's MAC address would then work. So then I reset my
> cable modem and we were back to square 1, despite the MAC address still
> being cloned.
> 
> A little background about DHCP: "Normal" operation dictates that the
> client broadcast a Discover packet, then the server sends an Offer
> directly to the client with the ip address being assigned. The client
> sends a Request to the server with that offered ip address, and the server
> responds with an ACK. However, there is a flag in the DHCP packet that
> can be set that says all communications should be done via broadcast. IE,
> the Discover, Offer, Request, and ACK packets are all addressed to
> ff:ff:ff:ff:ff:ff.
> 
> That's the key. I don't know everything about Charter's network, but this
> is what I deduce from playing with Ethereal for an hour or so. Charter
> does "authentication" via DHCP. In an "unauthenticated" state, the only
> thing that the modem sees is ARPs and DHCP broadcasts. Everything else is
> filtered. However, once you are "authenticated" by grabbing an IP
> address, you are able to receive unicast traffic. That makes the
> broadcast bit in the DHCP packet essential. If the client requests a
> unicast reply, it will never see it.
> 
> Looking at Ethereal dumps, it appears that my Linksys box does not set the
> DHCP broadcast bit. Neither does dhcpcd in its default mode (this can be
> changed by doing "dhcpcd -B eth0", at which time it works fine with
> linux). Windows's default mode is to set the DHCP broadcast bit.
> Unfortunately, it looks like the Linksys box does not have an option to
> set that bit.
> 
> But, you may ask (more likely, you've stopped reading by this poing ,
> why is the linksys box able to get an IP address after the Windows box (or
> Linux with the -B option set in dhcpcd) gets and IP address first? Well,
> the "tunnel" is already up; the modem is now receiving unicast packets.
> The linksys box sends a DHCP Request, requesting a unicast reply. And
> Charter's DHCP server sends a unicast reply. And all is good.
> 
> So what does a person like me do given this situation. Several things can
> be done:
> 1. Use Windows for the router.
> 2. Use Linux for the router, specifying the -B option to dhcpcd.
> 3. Use Linksys for the router, but doing #1 or #2 first to bootstrap the
> process.
> 4. Try to get ahold of an engineer at Linksys and suggest the ability to
> set a config option to specify what mode the dhcp client should use,
> broadcast or unicast.
> 
> For now, I'm doing #3 and #4. That being said, what do the rest of you
> do? Does only the WRT54G do this? Did you just give up on using Linksys
> products with Charter? Is Charter's behaviour in this manner specific to
> my segment? Tell me your story, Charter users...
> 
> Oh, and BTW, the performance seems good. Sunday evening and I'm getting
> about 750/115 on a 768/128k account, according to dslreports.com. YMMV.
> 
> RF
> _______________________________________________
> RLUG mailing list
> [email protected]
> http://lists.rlug.org/mailman/listinfo/rlug


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## bailenforcer (Sep 22, 2010)

Charter resets it's modems several times a day. Presumably to do two things. Force you to rent their combo modem/router at $10 a month, and to prevent non charter VOIP services. When the modem resets it provides an out of range IP address to the router you own and effectively shuts it down. 

Here's the stupid factor, Charter has made sure their techs are ignorant of this and each time a tech shows up it is a contractor company tech who is clueless. Their 1-888-438-2427 contract call centers is clueless also. Those techs couldn't troubleshoot a roll of toilet paper. They won't escalate your calls to a actual charter in house tech, they won't provide a list of compatible routers, because they want your to pay an additional $10 a month. So the customer is left totally frustrated. 

No wonder AT&T is taking all their business around here with their slower speed service. Good luck I have yet to find a router I can buy or spoof to accept the constant modem rebooting. I can't wait till AT&T Uverse gets here. 




etoft said:


> Hey heat...
> 
> I'm one of those Charter highspeed customers in Middle TN. I have a router between me and the cable modem (CM). When the router's DHCP lease times out, it often has problems getting renewing. I am not sure what the heck is happening, but IMHO it is most definitely on the Charter end. I bought a new CM...same problem. A new router...same problem. Connect computer direct to CM...same problem.
> 
> ...


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