Thanksgiving was pretty much as it has been for the last few decades, which is to say excellent.
Part of our annual thanksgiving ritual is to try to figure out the password for my grandparents’ wireless network. This year, that turned into something of a fiasco. Initially, the problem was simply that we could not remember the password. We tried a million combinations, with no luck. Eventually I decided to have a look at the router’s control panel, which is accessible from the iMac upstairs (the router is an Apple Airport Extreme). The iMac is also connected wirelessly, and the network password was stored but not readable.
When I opened the control panel for the router on the iMac, I was told to install a firmware update, and I clicked “OK”. After the firmware update, the device restarted, and all connections were dropped. When I tried to reconnect the iMac, I was prompted for the unknown password. Without the password I had no internet connection, so i gave up for the night.
In the morning, I used the hotel’s wireless network to look up how to reset the Airport. I performed a hard reset and configured the router with known passwords, which I expected would fix the problem. It didn’t. I could now connect to the wireless network with both the iMac and my Thinkpad, but the Airport refused to route to external hosts. The Airport is connected to a cable modem in the basement by a custom-spliced ethernet cable that runs through the walls.
This was strange behavior. As a stopgap, I thought to try plugging this ethernet cable directly into the iMac. It reported that no cable was plugged in, as would be expected if the cable were damaged. However, when I plugged the cable into my Thinkpad, I could acquire an IP address by DHCP and browse the web unimpeded.
So that is the situation as it stands. I have thought of two scenarios consistent with the evidence, neither of which sounds likely:
1. The cable is damaged. The damage is not so bad that packets do not flow, but bad enough that, on plugging in, a card might decide that the cable’s integrity is too low to initiate a connection. My Thinkpad’s ethernet card must be less demanding of quality than the ports in both the Airport and the iMac. Since the cable was working in the Airport before, the quality must have been fine the last time it was plugged in. It must have degraded over time, undetected until the connection was reset after the firmware upgrade.
2. The firmware upgrade changed the router’s behavior for DHCP requests. As a result, both the iMac and the Airport have incompatible DHCP with the DHCP server on the other end of the cable modem. My Thinkpad, running Linux, must have a more compatible implementation of DHCP.
That’s where it stands. To distinguish these scenarios, I intend to buy an ethernet cable tomorrow morning and try using it to connect the Airport and the cable modem. If I can then use the wireless network on my Thinkpad, the problem will be diagnosed and essentially solved. Otherwise, I don’t have any idea what’s going on, and someone else will have to be called in to fix the mess I’ve made.