On 02/12/2018 06:34 PM, Stephen John Smoogen wrote: > On Mon, Feb 12, 2018 at 6:25 PM H <agents at meddatainc.com> wrote: > >> Running CentOS 7 on workstation and having a problem with ssh disconnects. >> My ssh_config contains: >> >> Host * >> TCPKeepAlive yes >> ServerAliveInterval 30 >> ServerAliveCountMax 300 >> >> and sshd_config on the server contains: >> >> TCPKeepAlive yes >> ClientAliveInterval 60 >> ClientAliveCountMax 300 >> >> Have I missed any setting needed to prevent these random disconnects? I >> don't think there is anything wrong with the network card, the driver, or >> the cable, since if I am on a VPN connection via another server, the VPN >> and any ssh connection stay up indefinitely. >> >> Thanks. > > > There are usually 2 different reasons for this: > 1. The VPN is UDP and times out/drops keeps alives so that they no longer > function properly. [The UDP connection will make it look like you have a > new SSH connection which of course the system will drop because that would > allow for security problems.] > > 2. A firewall in the chain of things (system you are on, the system you are > going to, or somewhere in between) has session flushing issues. If you have > the firewall set up to only accept NEW port 22 connections and then just > looks to see if the ESTABLISHED, RELATED tables are accepted elsewhere then > if the session somehow ages out or is flushed due to usage, the ssh > connection can get dropped. > > The solution to one is to see if a TCP VPN fixes the problem. The second > one is to either make the iptables kernel tables larger or to have all port > 22 accepted even if it is not ESTABLISHED. > > These aren’t the only ways the problem you see can occur but they are some > of the most common I have run into. > > > >> >> _______________________________________________ >> CentOS mailing list >> CentOS at centos.org >> https://lists.centos.org/mailman/listinfo/centos >> Not sure if I am reading your reply correctly but I should clarify that I have problems when running naked ssh to the server, when I run ssh to the same server but over the VPN connection (that goes via third server) everything is flawless. I should also explain that: - I am on a workstation (located in the US), ssh-ing into server 1 (located in the US). - From server 1 I use scp to transfer large files from server 2 (located in Europe) to server 1 (in the US). The above randomly disconnects. However, when: - I use a VPN connection to server 3 (also located in Europe). - From the same workstation as above, do exactly as above, connections are rock-solid.