Diagnosing network problems

Yesterday turned out to be one of those days that makes me hate technology. First it started (actually left over from the previous week) where I could only sometimes access a server I use for my job. I no longer run that server, so all I could do was figure out the problem and tell the person in charge of it to fix it. Unfortunately or fortunately, I have the knowledge to figure out the problem. Turns out that the 2 DNS servers that are used for that server were returning different values, so depending on which DNS server got my request, would determine if I could connect to the server. Very frustrating, but at least I figured out the problem. The second major network problem had to do with my dad’s network. He had turned off all his equipment when he left on a trip and when he turned it back on, weird things started happening. His entire network uses DHCP, so it should have just worked, but I believe a bug in the firmware of his router (a Linksys WRT54g) was assigning the same IP address to 2 machines and his iMac was complaining. So after some futzing and me helping him, my dad updated the firmware on the router, restarted everything and was almost in business (I had to help him secure his wireless access point). He wanted me to teach him what I was talking about so that he wouldn’t have to call again, which I appreciate, but it seems that networking has a lot of vodoo in it, especially when you deal with a very mixed environment. He has a Windows XP Home edition PC, and iMac (OS X 10.4), an iBook (OS 10.3.9) connected via 802.11b, a Linux box running the SlimServer software (connected via ethernet), and a Squeezebox (connected via 802.11b). Since I helped him setup a bunch of the pieces, I end up being the only person that can diagnose the network.

Luckily the Linux box requires no user interaction and I set it up to use Zero Configuration so that it doesn’t matter the IP address of it so my dad can update his music and the Slimserver software also uses it, so it is easy to configure. The problem in this type of DHCP environment is sharing files. It would appear that Windows needs to know the IP address of the Mac in order to share files as my dad’s network has no master domain browser. This makes things extremely problematic if the IP address of the Mac changes. I could setup the Mac to use DHCP with manual addressing, but that didn’t seem to work. I have no idea what the problem was, but if I get a few hours, maybe I’ll re-investigate it. I wish things were easier, but they aren’t.

I’ve been doing computer networking of sorts for the last decade, so I have a lot of random knowledge about how things work and how to set things up. My own personal network is several times more complex than any home network because I run my own DNS server, use DHCP with static addressing (most machines on my network get the same IP address based on MAC address), and other weird stuff. I have more than a dozen devices on my network; sometimes I’m amazed that everything works.

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