Unable to Contact DHCP

I am having trouble contacting DHCP to get an ip and connect to the net.
I have searched the web for days......help me obi-wan kenobi, your my only hope!

It is a new pc is running Win XP pro service pack 1. I am connected directly to my cable modem via ethernet. My old pc (winXP home sp2) connects just fine with the same cable and modem. I have tryed The cmd release & renew. DHCP and DNS clients are started in services (i have tryed turning on almost everything else in services as well in desperation to see if i get a connection)
I have tryed installing the latest lan device drivers from my mobos website (I have 2 lan devices integrated on my mobo a 10/100/1000/ and a 10/100 I installed new drivers for both.) I have tryed Netsh dump and Netsh int ip reset reset.txt. I have tryed deleteing my network devices frm device manager and rebooting, I have tryed deleting winsock and winsock 2. I would say that my lan device is defective, but I tryed connecting through both of my mobos lan devices, could both of them be defective? the rest of my mobo works fine. This leads me to believe that it is a software problem. Sometimes i even recieve packets, but i still cant connect or renew my ip. And a few times It even got assigned an ip from DHCP, for about 2 seconds, then it just changed to invalid ip. most of the time it stays on the 169 ip. please if there is anyone out there help me!

 

Sounds like your ISP is doing MAC filtering. Call them and have them add your new MAC address to their data base.
Im sure you already know this but every NIC has it's own unique MAC (Electronic serial Number) also known as physical address.

 

ssmith10pn,

That doesn't sound right. The MAC address is a layer 2 address. It provides connectivity within the immediate Ethernet network. There is effectively an Ethernet network between the PC and the modem, but the modem will use a different layer 2 protocol (PPP or an ATM related layer 2 protocol) to connect to the ISP. Therefore the MAC address information will be lost at the modem.

However, I agree that ringing the ISP makes a sensible next step.

Magus_XI,

For another option, have you considered investing in a cable router? That will provide you with way of having both computers on the internet at the same time. Also your PC will have an easier job connecting to the router than a modem.

 

Not true Reggie,
My ISP does MAC filtering.
Why does just about every home router have a MAC address clone option?

You are correct in your theroy but not in principle.

Although after giving it more thought ushally when your MAC is not in the ISP's data base it will give you a private IP adddress that wont work instead of a public IP so that may not be the problem here.

 

To the best of my knowledge the only MAC address that the ISP is concerned with is the one for the Modem.

I was not aware that the Modem provided DHCP. I thought a Router was needed for that ?

And if you do have a Router have you powered down the Modem. the Router and the machines ? Make all connections. Then repower them one at a time. Modem first.

I had to do that just the other day after we had a power dip and I could not get any one of my three machines to go online. And the printer would not work either.

Very good suggestion. If a Router is not already there.

BillyBob

 

Have seen some of these newer Westell and Motorola modems that have both DHCP and built in firewall protection. Don't know, but might require cloning the machine's MAC address. You guys know more than this writer about networking but some of the newer modems require disabling features before they "play nice" with certain routers.

 

ssmith10pn is right

ssmith10pn,

You're right. I'm wrong.

After reading your comments I thought I'd better do some more thorough research to back up my arguement. The system used in the UK tends to be ADSL, and with that ISPs identify users by their telephone number. On reading up on PPPoE I realise that Cable DSL systems need to use a different unique identifier and therefore appear to use the MAC address of the PC that first connects to their service.

The good news is that this leads to a solution for Magus_XI, whose symptoms correspond to what you would expect if the ISP is using MAC address to authenticate access. MAC address is assigned to the network card (or the network card chipset within the motherboard if you have onboard NIC), by the manufacturer when the network card is made. The MAC address is unique (in theory) to the network card and not the computer.

Therefore if your ISP is using the MAC address as a first level authentication, and you change the network card, the motherboard with on board NIC, or the computer, this authentication will fail.

Magus_XI, you have two choices.

1. Set up your modem to clone the address from your original computer (or more precisely the NIC in it) if this facility is available.
2. Contact your ISP and ask them to add your new MAC address to their list.

A network connection's MAC address is listed when you do a IPCONFIG /ALL at the command prompt. It can also sometimes be found on a label on the network card itself. They usually have the form 00-XX-XX-XX-XX-XX where X is a hexidecimal number (0-9 and A to F).

The best page I found that gives information on this was this one on a Micro 2000 Tech Tips site..

Thank you ssmith10pn for showing me the error of my ways.

 

I do not undestand this at all. If using just the Modem it may be different. Or as Rockster2U mentioned a newer Modem.

But with the Router my ISP asigned IP and MAC address remain the same.

But the IP and MAC address of each machine can, may and has change(d) according to the order in which I have turned the machines on. At least I know the IP does. The MAC address I need to check on.

I believe that what NAT ( built into the router ) is doing is it translates the WWW address to the machines Network address. And in reverse it translates the network address to the WWW address.

Yesterday I took a machine that had been setting around doin nuttin for at least two years. Unplugged one machine and plugged the new one in and as soon as Windows 98SE was loaded BINGO ! I was online. Wouldn't that be the same as changing NICs ? The only thing I did see was down in the lower left corner of the the IE windows was the mention of " Checking Proxcy settings " ( or at least something about proxcy.) I saw the same on the on all 3 machines after I powered everything down the other day.

BillyBob

 

As I said in an earlier posting, the MAC address is tied to the network card. If you keep the same network card in the PC your PC's MAC address will remain the same (unless you have software soofing the MAC address).

NAT allows a router to appear as if it is the only computer connecting to the internet on the network. It then shares it's IP address with the computers hidden behind it. As far as the internet/ISP is concerned, the only device connecting is the router (it does not know nor care that in fact there are a number of PCs behine the router). So if you you use a NAT router, it doesn't matter which order the PC are added or switched on. It is the router that negotiates and is assigned an Internet address.

A modem connection is quite different. The modem provides the connection onto the network (it is in effect your network card for the internet) and your PC connects to the internet directly. It is therefore your PC that has to be assigned and negotiate an internet address.

 

Gaining but still a bit confused.

Router
Internet IP address==68.174.252.xxx
Sub Mask======255.255.255.0
Default Gatway=]68.174.252.1

The Internet IP is not the same as a few days ago before I had to shut everything down. Everything else is the same.

LAN IP address 192.168.1.1

So I see it as the Router connects the Internet IP to the Gateway and the gateway connects to the LAN IP.

In Reverse the Machine IP ( 192.168.1.100/103 ) sees the Internet IP as 192.168.1.1. And the Router takes it from there.

BillyBob

 

It worked!


I called my isp and they added my mac address and now everything works fine thanks smith! It would have called them sooner but because my other pc connected just fine I didnt think it was an isp problem. Thanks for showing me the light.

 

Glad it worked out.

Reggie, come on over to this side of the pond and I'll show ya the ropes.

 

Billy Bob

not sure if this will shed any light on your confussion or not but Magus_XI does not have a router, he is connected directly to his Modem which serves as a transparent bridge to the WAN of the ISP.

His PC gets a WAN ip address (Not a Private IP 192.168.x.x ) like you do.

 

Billy Bob,
The ISP that is serving you your WAN IP address probably has the Lease time set fairly low.
If you just release and renew in your router you will probably keep the same WAN IP. But if you left the router off for 15 min. you will probably get a diffrent one.

 

ssmith10pn thanks for the info.

That is what I have suspected. A Router would serve him well I believe.

That is just what happened. I believe I mentioned it before. But I had to power everything down to get things fixed after the power blip.

But are you sure ( right now I am not ) it is the Router and not the Modem ? I have had the Router off many times and the ISP assigned IP did not change.

But then again. Many times ( too many in fact ) what we think should or should not happen goes just the opposite.

Right now I am in the process ( only thinking right now ) of replacing my 4 port Router with an 8 Port so I can plug that spare PC in and use it for storage. No Video needed. No Audio needed. Just a very basic OS. A hard drive and a NIC. Actually would not even need a Browser.

BillyBob

 

Your current Router will hand out up to 253 addresses.
All that you need is a switch unless you want a new router with current technology.

 

Yup. That is a decison that I have to make. I could get an 8 port switch and connect it to the present Router. But I also think about a newer Router for the newer tech stuff.

I am leaning more toward the new Router because;

#1-Less hardware setting around. I am running out of room.
#2-I think it would be easier to setup.
#3-A few less ( at least 1 ) cables. I have enough of them to keep track of as it is.

BillyBob

 

BB - don't know if it will help or hurt but re: the MAC address thing:

each piece of network connecting gear you own (cards, router, etc.) has a unique hardware address burned into a chip and it stays the same, always.

Some systems are set up to make note of the MAC address when you first connect to them and after that, when you try to connect as would be the case if your stuff was off for a while and then turned back on, the system will first check the MAC address to see if the device requesting an IP address is one it knows about. If yes, an IP address is assigned. If no, an IP address is not assigned and you basically can't connect.

In your case, the MAC your ISP sees is the one burned into a chip on the router. For others who directly connect a single PC, it will be the MAC address of their network card.

If your ISP uses this particular security measure and you replace your router, a tech would have to reset so your new MAC was seen by their system as legit and so would be given an IP address.

As an example, when I first came to work where I am now, we connected internally via hubs that had this feature. When we first hooked a PC to a port on the hub we had to tell it to 'learn' the MAC address. After that, it would only assign an IP address if it saw that MAC. If the folks in an office moved their equipment around and plugged in to different ports, they could not connect to the network until they called and we reset the port to 'learn' mode and let it make note of a new MAC address while forgetting the old one.

The system worked well to keep people from moving equipment without telling us about it so we could update our equipment-locator database. It also meant no one could bring a PC from home and connect to the LAN so we knew we weren't having PCs on the LAN that didn't have proper AV software loaded.

In the case of commercial ISPs, I have no idea why some of them do the same sort of thing - can't see any real benefit to them - but a few certainly do.