Network follies

Michael Geary — Mon, 25 Apr 2005 21:19:50 +0000

I have lost all faith in my own intelligence.

I’d brought my ThinkPad over to my manager’s office to demo some network code I was working on. I had a couple of virtual machines running on the NAT network, so they could see other machines on the LAN as well as the host and each other. I unplugged the network cable, took the machine a few doors down, turned on the wireless network, and showed off my new code. Or tried to anyway. One little problem: The VMs couldn’t see the rest of our network through the wireless link. The host ThinkPad could ping other machines via the wireless, but the VMs couldn’t.

I’m pretty sure I’ve switched between wired and wireless connections using VMs with NAT before and it’s worked OK, or maybe I’m imagining it. In any case, it wasn’t working today. I fiddled with a few things, even tried rebooting the VMs, but never got it to work. The two VMs could see each other with no problem, so I just ran the demo that way. It was all I really needed anyway–virtual machines are great for demoing network software without having to carry a network around. But it would have been fun to show the connection to the rest of the LAN as well.

It wasn’t until hours later that I realized how easy it would have been to solve the problem: we could have simply taken twenty seconds to walk back to my office! We didn’t have an extra network connection handy in my manager’s office, but obviously I had the one I’d just unplugged. There was no particular reason we had to do the demo in one place or the other.

You’ve never done anything like this, have you?

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Network follies