Network Troubleshooting CheatSheet

Network Troubleshooting

What to check if site is down
------------------------------

1) check that A record is pointing to vps IP. I this case A should be followed by an IP.

dig ddailygirl.com

; <<>> DiG 9.7.0-P1 <<>> ddailygirl.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 5066
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;ddailygirl.com.			IN	A

;; Query time: 237 msec
;; SERVER: 192.168.1.1#53(192.168.1.1)
;; WHEN: Fri Jul  9 18:40:04 2010
;; MSG SIZE  rcvd: 32

2) Check domain through a proxy to make sure your local network/ISP is not blocking the site.

http://zend2.com/


3) Flush DNS

In ubuntu if you want to flush DNS cache you need to restart nscd daemon

Install nscd using the following command

sudo aptitude install nscd

Flush DNS Cache in Ubuntu Using the following command

sudo /etc/init.d/nscd restart