PING works but I cannot SSH. - ssh

Question

Machine A and B are trying to connect to machine C.
A gets there. When I do ssh -v ip, I get:
OpenSSH_5.1p1, OpenSSL 0.9.8j-fips 07 Jan 2009
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Applying options for *
debug1: Connecting to C.server.ip.addy [C.server.ip.addy] port 22.
debug1: fd 3 clearing O_NONBLOCK
Then there is more debugging that's not important.
B can't get there. When I do ssh -v ip, I get:
OpenSSH_5.9p1 Debian-5ubuntu1, OpenSSL 1.0.1 14 Mar 2012
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug1: Connecting to C.server.ip.addy [C.server.ip.addy] port 22.
debug1: connect to address C.server.ip.addy port 22: Connection timed out
ssh: connect to host C.server.ip.addy port 22: Connection timed out
The line that is never reached is:
debug1: fd 3 clearing O_NONBLOCK
What would cause this? Please help!

Answer 1

One possible cause may be a Firewall misconfiguration (A=>C on port 443 allowed, B=>C = denied).
In any case, if you have access to the C machine, put a packet sniffer like WireShark and check if the packets originating from B are actually reaching the machine.

Answer 2

I can think of several things that could cause this.
A firewall between B->C could block the connection. Are these machines on the same subnet? Is there a firewall? Such a rule would likely allow you to connect C->B. You can pull your files in this direction using scp. Something like
C$ scp user#B:/path/to/file /local/path/to/file
A tcpwrapper rule may have a similar effect. Do you have a rule in /etc/hosts.deny that blocks SSH from machine B? Check the man pages for hosts.allow and hosts.deny for info on changing tcpwrapper rules.
You should use nmap to check which ports are open and accessible from B and A. Something like the following should give you some good info. If port 22 is open from A but not B then one of the above is likely blocking it.
nmap -T4 -A -P0 -p0-65535 C