Basic Network diagnostics, ping.

Written by Tom on Friday 30/03/07

Yesterday afternoon the internet stopped working. Of course in this internet dependant world this was a disaster.

The first indication I had was that realVNC stopped working, I suspected that the Linux box I was monitoring had crashed (silly boy when do Linux boxes crash?) so I wondered over to the other end of campus to investigate.

The Linux box was up but I could not load any web pages.

Reboot the Linux box still no go.

Can ping the internet router but not Google.

Plugged the laptop into the internet router and I could surf the web and ping Google, very puzzling.

From the Linux box tried to pull up my knowledge base that resides on the Win 2003 server but could not connect. "Ha", I thought the win server has crashed (much more likely). Strolled back to the computer lab and the server was up.

It was then that a shred of my CCNA training came back.

Using ping I was able to dissect the entire network in under a minute and had isolated the break in the network.

One RJ45 had come loose or was knocked by someone, which disconnected the network from the Linux box. But why could I not surf the web from the Linux box itself? Because our Win2003 server does the DNS as well!! No DNS no surfing.

Ping is the Network Administrators friend.