Cable Forum - Modem to router works - modem to PC = no connection

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A$h X

29-04-2009 23:03

Modem to router works - modem to PC = no connection

As the title says, an ethernet connection from my modem to my router works perfectly, but a connection from my modem to my PC resulting in "acquiring network address" appearing for a long while and finally "limited or no connection" appears.

Occasionally the connection works, however if I disable or unplug or reboot the PC the connection fails again.
Via the router everything works fine, so this rules out a dodgy ethernet port on the modem, I think. Any ideas?

moaningmags

29-04-2009 23:05

Re: Modem to router works - modem to PC = no connection

Reboot the modem when you swap between the router and the computer.

xocemp

29-04-2009 23:12

Re: Modem to router works - modem to PC = no connection

And if that doesn't work and you have a 169 IP address its possible you may be sharing your nic mac with someone else. Ip's, mac's and dhcp what a bugger!

A$h X

29-04-2009 23:12

Re: Modem to router works - modem to PC = no connection

I reboot the modem if I cannot reconnect. Do I have to reboot the modem before I power up the PC?

moaningmags

29-04-2009 23:15

Re: Modem to router works - modem to PC = no connection

You used to be able to get away with not rebooting the modem but those days are gone and for the most part rebooting the modem is required, shouldn't have to reboot the computer though.
There's also the possibility of what that nice xocemp said.

A$h X

29-04-2009 23:16

Re: Modem to router works - modem to PC = no connection

Quote:

Originally Posted by xocemp (Post 34785571)

And if that doesn't work and you have a 169 IP address its possible you may be sharing your nic mac with someone else. Ip's, mac's and dhcp what a bugger!

I've noticed that my IP assigned by DHCP is sometimes 169.81.xxx.xx - I've often wondered what this means. Is there a "failsafe" static IP I could use (without a router) to get around all these DHCP shenanigans?
Or failing that, a way to make my modem work simply using an dynamic IP would be good.

moaningmags

29-04-2009 23:17

Re: Modem to router works - modem to PC = no connection

The modem does use dynamic IP.

A$h X

29-04-2009 23:22

Re: Modem to router works - modem to PC = no connection

Quote:

Originally Posted by moaningmags (Post 34785580)

The modem does use dynamic IP.

Quote:

Originally Posted by A$h X (Post 34785579)

Or failing that, a way to make my modem work simply using an dynamic IP would be good.

It obviously falls over at assigning my dynamic IP so you can hardly call that "working". I'm thinking perhaps to just clone my router mac to the PC directly connected to the modem, but TBH I shouldn't have to do this, any more ideas?

moaningmags

29-04-2009 23:24

Re: Modem to router works - modem to PC = no connection

You need to reboot the modem when you swap the device that's connected to it.
Then the new device asks the modem for an IP address, that's dynamic.
If you clone the MAC address from the router onto the computer you shouldn't have to reboot the modem.

zedsbb

03-05-2009 13:52

Re: Modem to router works - modem to PC = no connection

I've heard that some ISP's record your NIC MAC address and if you change NIC then internet no longer works. This may be happening with you. I'm not sure if VerminMedia do this or not. Just alter the PC NIC MAC to be the same as your router MAC.

Ignitionnet

03-05-2009 14:07

Re: Modem to router works - modem to PC = no connection

Quote:

Originally Posted by zedsbb (Post 34787602)

Never heard of an ISP do that. All that Virgin do if you change the MAC address connecting to the modem is change your IP address. Virgin are about the only ISP in the UK apart from Be / O2 who do not require a password to connect and use the cable modem for authentication purposes.

If you were to use the same MAC address behind multiple cable modems then you would get Virgin's attention.

Tech_Boy

03-05-2009 19:42

Re: Modem to router works - modem to PC = no connection

Quote:

Originally Posted by zedsbb (Post 34787602)

the modem will only give a connection to 4 unique MAC addresses per 24 hrs.
you can swap & change between those 4 as much as you like, but you cannot add a 5th (within 24 hrs).

If you cannot get a connection when connected direct (after rebooting the modem, waiting for the Sync & Rdy lights to lock solid BEFORE booting the PC), then you probably have a generic mac address on your nic, using the drivers within windows have been seen to cause this issue.

You could try using a MAC address changer or installing the specific drivers for your Nic.

Stuart

03-05-2009 19:50

Re: Modem to router works - modem to PC = no connection

Quote:

Originally Posted by A$h X (Post 34785579)

IPs beginning 169 are assigned by Windows (or Mac OSX) when the computer fails to pick up an IP from the modem.

Unfortunately, due to the way that Virgin Residential cable works, a "failsafe" ip that works as you describe is impossible. IF your ISP issues you a static IP, then you can do it, but if they don't, you can't.

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