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It's for a day that I can't login through SSH to my servers. Using both Putty and MobaXterm. MobaXterm ends with:

debug1: sending SSH2_MSG_KEX_ECDH_INIT
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
Read from socket failed: Software caused connection abort

I searched about the issue and found that it could be a MTU specific problem, but how is it possible to fail suddenly to login to different servers?

This is one of my debug enabled -v connecting sessions:

OpenSSH_6.7p1, OpenSSL 1.0.1g 7 Apr 2014
debug1: Reading configuration data /etc/ssh_config
debug1: Connecting to XXX.XXX.XXX.XXX [XXX.XXX.XXX.XXX] port 22.
debug1: Connection established.
debug1: key_load_public: No such file or directory
debug1: identity file /var/keys/.5380.ssh type -1
debug1: key_load_public: No such file or directory
debug1: identity file /var/keys/.5380.ssh-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_6.7
debug1: Remote protocol version 2.0, remote software version OpenSSH_6.0p1 Debian-4+deb7u2
debug1: match: OpenSSH_6.0p1 Debian-4+deb7u2 pat OpenSSH* compat 0x04000000
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: server->client aes128-ctr [email protected] [email protected]
debug1: kex: client->server aes128-ctr [email protected] [email protected]
debug1: sending SSH2_MSG_KEX_ECDH_INIT
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY

It hangs at this line and after seconds ends with:

Read from socket failed: Software caused connection abort

I really appreciate any help.

4
  • Is any other communication working to your servers? Can you ping them, can you use any other services hosted on them? Not sure why you would jump to a conclusion about mtu settings. Are they on the same layer 2 network as you or is there some kind of router/firewall between you and them. Do you see anything wrong on the servers if you login at the physical console?
    – Zoredache
    Mar 20, 2015 at 22:50
  • Thanks @Zoredache, yes I've no problem in pinging and accessing domains hosted and there is no firewall between. I can login through VNC yet with no problem but can't login through SSH. Almost every topic I encountered about this issue ended with MTU specific problem so I thought it would be the culprit.
    – rev
    Mar 20, 2015 at 23:14
  • If you really suspect mtu as being a problem trying pinging it with the no fragment options set and the packet size at the maximum for that network.
    – Zoredache
    Mar 20, 2015 at 23:18
  • @Zoredache If I didn't do it wrong, I found the optimal MTU (970) adding 28 to it and changed it directly via router configurations. Still I can't reach servers by SSH. Weird!
    – rev
    Mar 20, 2015 at 23:23

1 Answer 1

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looks like you are having an issue with ssh key on the server/client... have a look at https://askubuntu.com/questions/205179/ssh-problem-read-from-socket-failed-connection-reset-by-peer (slightly different error but most of the socket errors are similar troubleshooting wise.. )

and also clear known host file when you re try connecting from laptop/desktop for example MobaXterm you have to navigate to /home/mobaxterm/.ssh/known_hosts and remove existing entries.. for putty check this https://superuser.com/questions/197489/where-does-putty-store-known-hosts-information-on-windows

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