Modem assining ip instead of router

May 31, 2010 at 20:18:45
Specs: Windows XP
I'm trying to get my Motorola SB4100 + linksys WRT54G to share out my new road runner cable connection, problem is the router will not assign an ip address to the computers NIC but the Motorola modem assigns the ip address instead. I can get online fine with the pc that is already directly connected to the router and modem but not the other pc that is accessing it via wireless.

The wireless connection can access the router but cant get out to the internet.

What can I do to get the router to assign an ip address to the directly connected pc instead of the cable modem? Or what else can I do to get the router to share the connection? its as if the nic doesn't even see the router the only way i can access it is if i set the ip address to 192.168.1.1 as the default gateway on the tcp/ip properties page in winxp but then i cant access the modem though the router i tried setting it with dhcp with the dns set from the modem. That did not work, then i tried setting the router to static mode and set the ip address that was from the modem set for the pc's nic to the router. Still nothing...i cant manipulate any of the settings in the cable modem either there's no option to bridge the Ethernet connection in the modem or edit anything with ip addresses. Do you think I should ask time Warner for a new modem that supports bridging? Or should I get another router...?

I don't know what else I can do to get this thing working.

There's a few ip address i have to deal with
one is the HFC IP Address
Then there's the static ip address which is what the modem is assigning the PC's nic + the gateway ip which is also being assigned.
Then there's the internal ip address of the modem itself which is 192.168.100.1 to access the modems configuration page which is useless since there are no things you can set in there to manipulate the ip address.


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#1
June 1, 2010 at 06:22:40
There is probably an interface for each of the devices & they have to be accessed separately. Connect a PC directly to the modem & change the settings using the IP you mentioned.

Then connect the router & open the router interface. Change those settings to whatever you want. Everything should be set to the same subnet.

How do you know when a politician is lying? His mouth is moving.


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#2
June 1, 2010 at 06:51:05
There is no manipulation for the modem, in otherwords you can not change anything in the modem only the router I can configure.

The problem is that the modem is simply not allowing the router to assign the ip address to the pc directly connected to the router + modem via the 4 ports on the back of the router. You can NOT change anything in the SB4100 cable modem only the linksys WRT54G router can have its settings changed but the modem keeps assigning the 65.x.x.x address instead of getting a 192.168.1.x address from the router. is there any way to fix this?

[edit] Another problem is the subnetmask the modem assigns a 255.255.254.0 subnetmask and i dont think the WRT54G supports it. Is there any router out there that supports 255.255.254.0 subnetmask? or is this a just a tcp/ip problem?


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#3
June 1, 2010 at 08:39:30
I am sorry but your assessment as to what is going on can not be correct.

"but the modem keeps assigning the 65.x.x.x address instead of getting a 192.168.1.x "

Here is your confusion. The ROUTER assigns 192.168.1.x not the modem. The modem is assigning the correct ip and it should be going to the wan interface of the router.

From what you write the modem is acting correctly. Make sure you have cabled correctly ie modem lan to router wan port.

You can't change the modem so take it out of your thinking. Whatever it assigns is correct.

If the routers wan port is getting the correct 65.x.x.x ip and you can get on the internet via a pc to modem connection, you may need to clone the workstations mac address to the routers wan port. Most routers have a button on the wan interface page like "clone workstation mac address" or have a place to manually input the mac address.


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#4
June 1, 2010 at 12:57:18
no the modem is connected to the routers lan port because the WAN port does not work when connected to it. I think the problem is the routers WAN port itself (i may have to get another router). it does assign me the proper ip when the modem connected to the internet (wan) port on the WRT54G but it does not let me access the internet even when i assign the right ip's staticly in the router. But when the modem is plugged into a LAN port with the other lan it works only on the directly connected pc. i'm sure it has something to do with this 255.255.254.0 subnet because by default in the linksys setup page there is no option in the dropdown box for a 255.255.254.0 subnet. There is only 255.255.255.0,128,192,224,244,248,252 selectable but not 254.0

Where did i get this from? A simple google search with the terms "linksys 255.255.254.0 or linksys subnet"

http://homecommunity.cisco.com/t5/W...

http://fixunix.com/routers/78896-li...

http://www.techspot.com/vb/topic706...

these links are probably similar to what my problem is because of the subnetmask class range.
still not sure how to fix it right.


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#5
June 1, 2010 at 13:15:57
NiceTie you are chasing your tail in the dark.

You don't plug the modem to the lan port of the router AND expect dhcp to work. The first pc requesting a dhcp ip will get the modem's provide ip. No other pc will get on the network.

"it does assign me the proper ip when the modem connected to the internet (wan) port"

OH? So it is not assigning a 65.x.x.x ip? You seem to think it should assign a 192.x.x.x. Set the wan port to dhcp and clone the mac address as instructed previously.

Concerning your first link you missed that it is talking lan ports not wan ports
"Linksys routers don't allow you to use larger LAN masks"

You can go down this path all you want to but it will be to no avail.
Your assessment is incorrect and has nothing to do with subnet mask.

Solution:
Properly connect the modem to the routers wan port. It appears the modem is providing a dhcp ip. Connect to the router via a pc and go to the routers wan page to confirm it is set to get a dhcp ip.

Start here and post back once you have confirmed the routers wan port has the ip.


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#6
June 1, 2010 at 18:00:58
i got the problem fixed it WAS in fact the subnetmask of the modem that it was assigning the router and it does not support it, because i tried it on another router that i just bought (a netgear WGR614v9) and it works just fine and the subnetmask is set to 255.255.254.0 in the new router. let this be a lesson to anyone who wants to buy a linksys WRT54G router, don't get it if your ISP has a subnetmask range of 255.255.254.0 because linksys routers (or at least the WTR54G) does not support that subnetmask range.

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#7
June 2, 2010 at 05:53:46
That still doesn't sound right.

How do you know when a politician is lying? His mouth is moving.


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#8
June 2, 2010 at 07:28:08
let this be a lesson to anyone who wants to buy a linksys WRT54G router, don't get it if your ISP has a subnetmask range of 255.255.254.0 because linksys routers (or at least the WTR54G) does not support that subnetmask range.

Unless you called Linksys support and they told you this, I'd have to say you're dead wrong. I'd bet you didnt' call them and are assuming.

I've had opportunity to work on several different Linksys models and I've never heard of one, nor worked on one, that didn't allow changes to the subnet mask. I use many WRT54GL's here at work as wireless access points for our public "guest" wireless network and they're all fully configurable.

It seems more likely there's something wrong with the unit you have. I can't see Linksys (which is owned now by Cisco) saying to themselves, "Ok guys, just for grins and giggles, we'll make it so the WRT54G can't use any subnet mask except 255.255.255.0 but we'll make every other model me manufacturer fully configurable."

Think about it, does that make sense to you?

From the sounds of it, there's either something physically wrong with that unit or the firmware is having issues. If you haven't yet, try updating to the most recent firmware. If that doesn't fix the issue, or you already have the most recent firmware version available, try a 3'd party firmware like Tomato or DD-WRT If none of this works, then something is physically wrong with the unit.


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#9
June 2, 2010 at 07:50:50
"got the problem fixed it WAS in fact the subnetmask of the modem that it was assigning the router and it does not support it, because i tried it on another router that i just bought (a netgear WGR614v9) and it works just fine and the subnetmask is set to 255.255.254.0 in the new router. let this be a lesson to anyone who wants to buy a linksys WRT54G router, don't get it if your ISP has a subnetmask range of 255.255.254.0 because linksys routers (or at least the WTR54G) does not support that subnetmask range."

What are you talking about. All you had to do was change the subnet mask on your WAN port and it would have worked fine. I love the WRT54G router and since I put white Russian WRT on it it is even better.


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