I have this problem which gets to be really annoying. I will login to a remote machine (say test.machine.com) via ssh and everything will work very nicely. Now, sometimes I will disconnect and reconnect back and everything will be OK. But, sometimes I would just get this:

ssh: test.machine.com Name or service not known

Sometimes this is very annoying since I have to sftp oftenly many times a day. I'm definitely sure that the machine still works since when I type in the IP manually like

$ ssh 123.456.789.123

It will work. Also, it works from other machines so it's not like the DNS disappears. What could be the problem, I had this on Slackware and Arch and I'm completely lost...

points to a dns issue

1. your dns servers are flaky
2. the dns server hosting machine.com could be flaky

Hello,
Thank you for such a quick reply. The thing I don't understand is that, say I am in the computer lab (the machine.com is a computer in the physics department), I can easily SSH from the computer lab, but if I SSH to my home machine and try from there to SSH to machine.com I'd get the Name or service unknown. So, I guess the DNS is flaky towards my home computer only

there is a possibility that this "123.456.789.123" is a private address and not published on any of the external (public) dns servers.

If are always unable to connect to the lab systems from home, the above may be true.