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No route to host in one direction

br flag

I am able to ssh from one host in Mexico to another in New Jersey, but when I start the ssh from the New Jersey host going to the same Mexico host, I get "no route to host". While troubleshooting with tcptraceroute I see that the last 2 ip addresses are duplicates; traceroute hits an infinite loop and stops.

I have 2 questions. What is the magic that allows packets to return from New Jersey to Mexico, but not initiate from New Jersey to Mexico?

Are there any workarounds to this problem, or do I need to switch network providers?

raj avatar
cn flag
raj
Isn't the host in Mexico behind a NAT or firewall? That could be a pretty common cause of being able to initiate connection in one direction only.
user535733 avatar
cn flag
The other question "*Are there any workarounds to this problem, or do I need to switch network providers?*" currently has insufficient information to be answerable. It can probably be fixed (not worked around), but we would need basic information about your Mexico network to guide you in the right direction.
br flag
It seems that ISPs in Mexico commonly use double NATing which was the cause of my problem. FIOS has NATing at the router inside my house which I control and can do port forwarding. In Mexico, the providers have a second NAT device upstream from the house. As far as I know NAT only allows the initiation of the connection in one direction. My work around is a reverse SSH Tunnel started from systemctl.
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