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Hi everyone,
I'm trying to set up a new server in a network and encountering some funny behavior. The first thing was that I'm unable to ssh into the new machine (from a different machine) even though I'm fairly confident that iptables is set up correctly (and it doesn't work with iptables off either).The second thing I noticed when trying to debug this issue is that when sshing out of the new machine the session will fail in a few seconds with a message of "Write failed: Broken pipe". I did some searching and saw that some people found that reducing the keep alive packet time in the ssh config helped but it did not for me. There's no proxy between the machines and they are in the same subnet so I don't think that there's anything that would break an idle connection. These symptoms sort of suggest that someone else might be using the same ip address (they aren't "supposed to" but a lot of people have access to ports and might've just picked randomly until one worked). I tried to check using nmap (nmap -sS -P0 new_host) when the new machine was off but it said that the host was not up. If I run nmap with the machine on then it sees it but says that all ports are filtered (again both with and without iptables). There are a lot of variables here but maybe somebody more knowledgable than me can see something obvious.
Thanks for reading!
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I just made a big discovery. Both of these issues only occur when these two specific machines that I'm working with. Either machine can make or receive ssh connections with any other computer in the network but when they try it with each other they get the behavior mentioned above. This helps narrow down the cause of the problem significantly but I still don't know what it is exactly. Something else that is relevant is that these two machines are on the same switch.
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