This weekend I decided to rearrange my office/computer room/workspace because I had added a new gun safe. As part of this I dismantled my home network, including my cable modem.
When I went to put it all back together, I noticed that my Linux box wasn't getting a response from the DHCP server. I checked the cable modem and saw that the cable light was on and the data light was flashing. However, the PC light was off and the hub¹ didn't show a light for the cable modem. I swapped the hub for a spare. No luck. Then I tried a different ethernet cable, in case the first one was bad. Still no luck.
At this point I'm starting to think the cable modem has gone bad. That sinking feeling starts to settle in as I'm thinking I'm about to be without internet access for an extended period of time. Kind of like a junkie without a fix.
After a while (as I'm about to head out to buy a replacement cable modem), I remember that cable modems have the TX and RX wires reversed, so that they can use standard ethernet cables when connecting directly to a PC (rather than more expensive crossover cables). To use them with a hub they have to be connected to the uplink port. I moved the connection to the uplink port and all was well again.
Oh well, nothing of great importance. But beware of acute dumbass attack when reassembling your network setup.
¹ I use a Linux PC as a masquerading firewall. It has two ethernet cards, one goes to my internal 10/100 switch and the other goes to the 10Mbps hub that the cable modem is connected to. I suppose I could ditch the hub and connect the firewall directly to the cable modem, but I like the flexibility of being able to plug in directly without rewiring if something goes wrong with the firewall. One of these days I'm going to get a dedicated firewall and ditch the Linux firewall (Linux is fine, but I'm getting tired of building and maintaining PCs and their associated hardware).
Posted by Aubrey at October 28, 2002 11:45 AM