I'm trying to cut down the time ssh is trying to open a connection to a host. If I put for example ssh www.google.com it takes very long until the prompt comes back.
I read about using ssh -o ConnectTimeout=10 www.google.com instead, but even this takes very long. Is there maybe a number of attemps I can modify to decrease the blocking time?
Answer
The problem may be that ssh is trying to connect to all the different IPs that www.google.com resolves to. For example on my machine:
# ssh -v -o ConnectTimeout=1 -o ConnectionAttempts=1 www.google.com
OpenSSH_5.9p1, OpenSSL 0.9.8t 18 Jan 2012
debug1: Connecting to www.google.com [173.194.43.20] port 22.
debug1: connect to address 173.194.43.20 port 22: Connection timed out
debug1: Connecting to www.google.com [173.194.43.19] port 22.
debug1: connect to address 173.194.43.19 port 22: Connection timed out
debug1: Connecting to www.google.com [173.194.43.18] port 22.
debug1: connect to address 173.194.43.18 port 22: Connection timed out
debug1: Connecting to www.google.com [173.194.43.17] port 22.
debug1: connect to address 173.194.43.17 port 22: Connection timed out
debug1: Connecting to www.google.com [173.194.43.16] port 22.
debug1: connect to address 173.194.43.16 port 22: Connection timed out
ssh: connect to host www.google.com port 22: Connection timed out
If I run it with a specific IP, it returns much faster.
EDIT: I've timed it (with time) and the results are:
- www.google.com - 5.086 seconds
- 173.94.43.16 - 1.054 seconds