[CentOS] unreachable peer

[Gordon Messmer]

On 05/16/2015 10:23 AM, Leon Fauster wrote:
> Well, the destination is not in my realm (different provider). Before
> contacting them I want to be sure that my system is not causing this.
> So far i just see a "tcp retransmission" while trying to establish
> a https connection (captured on our router):

That can be difficult to establish.  If you're getting no response, the 
most likely problems are either a bad route or a firewall rule somewhere 
along the path.  The problem could exist at anywhere along the path, and 
they'll typically both look the same according to tests at your host.

As Anthony pointed out, you can use hping3 in TCP traceroute mode to 
determine where along the path the problem probably exists.  The first 
host to not respond should be the host with the problem.  Hopefully you 
have access to a host that has access and a similar path to the host you 
can't reach.  If so, the same hping3 command should give you the 
complete traceroute path, and from there you can find the host that 
didn't respond in the first test.