Originally Posted by lanbrown

I had this issue with my mom’s connection; she too has Comcast. The router “quit” working, but if she plugged the computer directly into the cable modem it would work. After having her reset the router and such, it still didn’t work. She sent me the router and I got it to instantly work at my place (not Comcast.) Since I was going back to Michigan for a few days, I just brought the modem back with me and once again, it didn’t work with Comcast. Long story short, they were NOT releasing the IP address and only allow ONE per customer. So basically the PC had it and there was no way to get the modem to work unless they clear the lease. Which they say they cannot do as DHCP does not allow that. After berating first, second and third level support, telling them they don’t know what they’re doing, are useless and should invest in technology that not only supports standards but allows the people who are suppose to provide support the ability to do so.

As a little history, a little company called Cisco wanted to put me at one of their client sites, which just happened to be a cable provider. I didn’t take the job, I can’t stand telcos and the cable companies are just as bad.

To save yourself the hassle, do two things. The first is to clone the MAC on the router. Since Comcast isn’t releasing the lease and they will only provide an IP from that MAC to your cable modem, you need clone it. This can cause a conflict with some routers, as all routers have ARP entries. This is where Layer 2 (MAC Address) gets mapped to Layer 3 (IP addresses) and you have the same MAC, two IP’s on different sides of the router. The Linksys I used at my mom’s place didn’t like the same MAC on both sides of the router. The code has been quite buggy with it as well. Since the NIC in the computer wouldn’t allow me to change the MAC, I made sure I brought a spare NIC with me; placed that in the computer and away it went. It’s been running since May with no problems.

In your case, clone the MAC from the desktop, see if the router gets an IP and use the laptop. If it works, then plug the desktop in and see in your router is happy with the same MAC on both sides of the router. If not, then you will have to get another NIC if you cannot change the MAC.

PM if you need more help.