SSH Client Reset

Issues related to configuring your network
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SSH Client Reset

Post by tyrhoads17 » 2018/01/11 17:06:55

As I'm working from my client machine and SSH into a CentOS 7 machine I frequently drop connection. I'm using Putty to SSH. I am activity working through SSH so inactivity shouldn't be an option for losing connecting. The client Ip is: CentOS 7 ip is: I looked on the switch and here is the results:

Generate Time Source address Destination address Destination Port Bytes Sent Bytes Received Packets session_end_reason
1/10/2018 17:22 22 9906 8908 131 tcp-fin
1/10/2018 16:50 22 16180326 143857862 256585 tcp-rst-from-client
1/10/2018 16:17 22 2431360 3965330 9064 tcp-rst-from-client
1/10/2018 16:17 22 16874270 669155454 693822 tcp-rst-from-client
1/10/2018 13:14 22 38520968 202959918 878105 tcp-rst-from-client
1/10/2018 10:56 22 12256 23734 119 tcp-fin
1/10/2018 9:12 22 12744 12972 173 tcp-rst-from-client
1/10/2018 9:12 22 75372 126990 1368 tcp-rst-from-client

The client does a TCP reset. Putty will fail and show " PuTTY Fatal Error Network Connection: Software caused connection abort." View attached picture for image. I have Keepalives turned on in PuTTY. Seconds between keepavlives in 55. I also re-installed puTTY 0.70. My question is does anyone have any idea why my client machine (windows 7) does a TCP reset and drop connection?

PuTTY error
PuTTY error
Capture.PNG (29.86 KiB) Viewed 1144 times

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Re: SSH Client Reset

Post by TrevorH » 2018/01/11 17:17:24

Are you sure you don't have something else on one of those ip addresses? The symptoms you describe are often caused by a duplicate ip address on the network.
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Re: SSH Client Reset

Post by tyrhoads17 » 2018/01/12 12:40:58

I checked that and there are no duplicate IP on the network.

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Re: SSH Client Reset

Post by rotorboy » 2018/07/28 15:58:41

I seem to be having this same issue. I have around 50 CentOS 6&7 VM's in our network. All of the VMs use the iptables for firewalld and have ssh port opened. Hosts allow/deny is set up and only allows IPs within certain IP ranges to connect to SSH. On most servers SSH connections are stable but on some the connections are very much unstable. Connections will drop seemingly at random and often when they drop it may take a minute or two before I can re-establish a connection. That new connection may last seconds, minutes, or even hours.

On the client side we're using MobaXTerm and mRemoteNG (Putty). Keepalive is ON.
On the server side almost everything is stock settings for CentOS except I've tried messing with these:
X11Forwarding yes
TCPKeepAlive yes
ClientAliveInterval 120
ClientAliveCountMax 10

The VMs have multiple IPs running, sometimes on multiple interfaces but mostly on virtual interfaces. I checked for duplicate IP usage on the network but there's no indication this is happening. If it was we'd be having a lot of other problems as well. I've just gone ahead and set the loglevel to DEBUG to see if I can find anything else. In the meantime I though I'd share this as this problem has been here for some time now.

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