Was doing a minor wireless network for a boarding house... there is one cable modem (a motorolla surfboard) for broadband cable internet access... the ethernet cable goes from there to a Netgear dual band wireless router. Then, another ethernet cable goes upstairs to another wireless router (the first router's range isn't good enough to reach 4 floors up). Connectivity from all network devices is great. I can connect to the wireless upstairs (a Linksys wireless G router) and I can also connect Wired to either the upstairs Linksys router, or the downstairs Netgear router. The problem, however, is that the motorolla surfboard seemed to die.
I was upstairs testing connections the the linksys when I tried pinging out of the network to google.com and cnet.com. The requests started timing out and it appeared that it was the DNS servers that was causing it... I went downstairs and connected wired to the comcast modem, which appeared to have a bad port in the back (the ethernet port was bent in, and the network cable wouldn't clip in firmly). I wasn't getting an ip address from the modem. I was just getting a 169.254 address. I then connected the modem to the internet port of the router down there, then connected wired to the router myself, and went to the router setup page, and checked the status there - the modem was also not giving the router an IP address (even though it had been working fine earlier). I then tried with another ethernet cable, just to be sure, and had the same issue.
Long story short, I left telling everyone that the modem is toast - and in my opinion it really is - but the next day everything on their network was working fine again. My best guess is that the modem is going down hill, and the overnight rest it had was enough to get it to keep going the next day.
So it seems the modem is at fault... anyone else care to second that?