Mass resolve ip to hostname
Answer:
If you have a list of IPs and need to resolve to the hostname(via reverse DNS lookup), you can use the following command:
cat ip_addresses.txt | xargs -n 1 -P 100 -i dig -x {} +shortJun 122014
Aug 022013
How to show all listening ports in Mac OSX
Answer:
To show all the listening ports in Mac OSX, try
# lsof -iTCP -sTCP:LISTEN
Jul 182013
How to check how many established connection of my web server?
Answer:
Assume you server is listening on port 80, you can check how many established connection to this port with the following command:
netstat -an | grep :80 | grep ESTABLISHED | wc -l
4919
Mar 092013
Traceroute using TCP
Answer:
It is common now for a server to disable the ICMP and make commands like *ping* & *traceroute* failed to do the diagnostics. However, newer version of *traceroute* have a TCP mode that if you know a particular server is opening a port for TCP connection, then you can use command like..
# sudo traceroute -T www.google.com
traceroute to www.google.com (74.125.235.242), 30 hops max, 60 byte packets
1 136.182.34.2 (136.182.34.2) 0.557 ms 0.572 ms 0.621 ms
2 125.235.129.111 (125.235.129.111) 11.232 ms 11.242 ms 11.235 ms
3 otejbb205.int-gw.kddi.ne.jp (124.215.194.161) 1.602 ms otejbb206.int-gw.kddi.ne.jp (124.215.194.177) 2.123 ms 2.119 ms
4 ix-ote210.int-gw.kddi.ne.jp (106.187.6.114) 11.182 ms ix-ote210.int-gw.kddi.ne.jp (106.187.6.98) 11.156 ms ix-ote210.int-gw.kddi.ne.jp (106.187.6.114) 11.199 ms
5 203.181.102.94 (203.181.102.94) 63.248 ms 63.272 ms 63.262 ms
6 209.85.249.195 (209.85.249.195) 2.523 ms 2.252 ms 2.191 ms
7 64.233.175.0 (64.233.175.0) 6.512 ms 6.448 ms 6.537 ms
8 64.233.174.0 (64.233.174.0) 11.154 ms 11.474 ms 10.738 ms
9 216.239.43.243 (216.239.43.243) 11.108 ms 11.713 ms 12.141 ms
10 kix01s02-in-f18.1e100.net (74.125.235.242) 11.103 ms 10.582 ms 10.882 msFeb 212013
Diagnosing network connectivity with mtr
Answer:
To check the network connectivity to a specific server, you can use the mtr command.
e.g.
# mtr --report google.com
HOST: localhost Loss% Snt Last Avg Best Wrst StDev
1. 106.187.33.2 0.0% 10 1.3 5.3 0.6 21.4 6.7
2. 124.215.199.121 0.0% 10 0.6 6.5 0.4 12.4 4.8
3. otejbb206.int-gw.kddi.ne.jp 0.0% 10 2.1 3.7 2.1 12.5 3.3
4. ix-ote210.int-gw.kddi.ne.jp 0.0% 10 2.1 6.4 2.1 15.2 4.5
5. 203.181.102.94 0.0% 10 2.6 2.7 2.2 3.9 0.6
6. 209.85.249.195 0.0% 10 3.2 5.3 2.3 22.8 6.6
7. 64.233.175.0 0.0% 10 7.0 13.5 6.8 49.8 13.7
8. 64.233.174.0 0.0% 10 20.0 12.7 11.1 20.0 3.0
9. 216.239.43.145 0.0% 10 12.0 11.8 11.5 12.2 0.2
10. kix01s01-in-f8.1e100.net 0.0% 10 11.2 11.4 11.1 11.9 0.3
