Re: Troubleshooting Techniques

I don't really have a quick reference written out yet, but troubleshooting
is a methodology, a mindset...This is a quick guide to my personal way of
thinking about things when something goes wrong...

1) Verify the issue -- Sometimes "the internet rebooted" means an email
server is down : ) Make sure you verify the issue.

2) Know the technology -- I know this seems obvious, but you can't FIX
something if you don't know how it is supposed to work. Know how things
look and behave when it is functioning, and know how they behave when things
are broken.

3) Start at the source, and narrow things down -- This is the meat of
troubleshooting. I like to start at the source and work towards the
destination. I also would recommend you start at Layer 1 and work your way
up the OSI stack. Never troubleshoot BACKWARDS in the OSI model! For
instance, if you can't PING the other end of a frame-relay link, but you are
having a BGP peering issue...well you need to go back and figure out why you
can't ping first, before you waste your time on BGP. It could be a L1, L2,
L3 issue...

4) If you follow step 3, you will hopefully eventually narrow things down
and find the specific issue or issues. Now it is time to fix...this is the
easy part and usually involves configuration, or fixing some wrong
configuration

5) Verify (again) -- Now you verify that what you did actually fixed the
problem.

Just my 2 cents notes...

On Fri, Sep 25, 2009 at 6:01 PM, Johnny B CCIE <jbccie_at_gmail.com> wrote:

> Does anyone have a quick reference for troubleshooting that they use for
> the
> lab? Maybe we should make one for each layer of the osi model, each
> protocol, and some of the features we commonly use. How do we troubleshoot
> DHCP, NAT, WCCP, IRDP, DRP, Spanning-Tree, Multicast, and BGP? If we
> discuss
> it surely we can refine our methods.
>
>
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-- 
Regards,
Joe Astorino - CCIE #24347 R&S
Technical Instructor - IPexpert, Inc.
Cell: +1.586.212.6107
Fax: +1.810.454.0130
Mailto:  jastorino_at_ipexpert.com
Blogs and organic groups at http://www.ccie.net