Monday, 2 September 2013

Why Basic checkups and close observation are important during T-shooting? NTP server issue/ Broadcast Storm.

Hey Mates,

New Post for you guys :- I was doing a troubleshooting for othe Internet Connectivity that we have in our Infrastructure. The Internet completely stopped working and user as usual became restless like their life support was snatched from them. This was a Cisco 2921 router.

Before I did anything I jumped in the logs. (BIG Mistake) and found all the logs related to July.. I thought there was no recent change made according to the logs and started to search here'n'there haphazardly.

After some digup I found the port is down and then i just gave "no shut" command. The port didn't came up.
Then I again ran through the router logs and found that logs were incorrect!! The timing was incorrect!! (It was july 1994 default date)  The NTP servers were not correctly configured. I gave  "Show Clock" command and found I was right!!

Then I went  to the interface and brought it up by giving  "Shutdown" and then "No shut". That actually brought it up.

So 2 learnings here :-

1) Keep your eyes open and be sharp on what you are looking. It may be boring but skim your eyes through the whole content and then come to conclusion. It wouldn't hurt to spend some seconds before coming to the content.

2) If you want to refresh an Cisco Interface "ALWAYS GIVE "SHUT" and then "NO SHUT".

AND YES the problem was happening due to Broadcast storm generated by one of the machines in the access switch chain. We had put a command in our switches to put it into "Shutdown" mode if the broadcast storm is received.

Keep Learning guys!!! :)

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