Network Troubleshooting

I am a cisco rookie....still trying to get my feet situated properly in the field. I just completed a CCNA training, though coming from a Unix background, everything feels different to me. I need resources on troubleshooting, how do i approach a downed network, what should be my troubleshooting guidelines?

I am a cisco rookie....still trying to get my feet situated properly in the field. I just completed a CCNA training, though coming from a Unix background, everything feels different to me. I need resources on troubleshooting, how do i approach a downed network, what should be my troubleshooting guidelines?

Well, for starters:

(1) Can anyone connect to the internet, or it it only limited to one or two people?

(2) Does the internet router supply NAT/DHCP, or is it in bridged mode to an internal router/firewall?

(3) Can you ping the internal gateway address? Can you ping the external IP address?

(4) If you connect a PC directly into the internet router, can you access the internet?

Your troubleshooting methods are going to vary from issue to issue.

In its basic form, you have 3 options:
1. troubleshoot from the outside in
2. troubleshoot from the inside out
3. split the difference and start in the middle, working your way out/in, then go the other direction.

In general, networks don't usually just die. The problem can usually be traced back to Carrier issues, Misconfigurations, bad cables, or 'acts of god' -ie: storms causing power outages.

-In the case of a misconfiguration, back out everything you just did and see if the problem goes away.
-In the case of carrier issues, once discovered, call your ISP.
-Bad cables are usually an issue right away. Replace it or remake it if you roll your own.
-Acts of god need to be evaluated on a case by case basis and will vary based on the damage done.

nnbnbhi there,
again from my archives, here's a link which you can use as a guide to network troubleshooting
support.3com.com/infodeli/tools/netmgt/t...t/091500/c1ovrvw.htm

Great advice from Arani
One thing to add; approach your network before it breaks. Survey and document it. That way when it does break you'll have a good grasp of the topology and you'll be able to select logical places to test and break the problem down. And also you'll know what 'normal' looks and feels like so the abnormal will be obvious.
You can faultfind without these extras but they really do help speed things up