Today, when I tried to connect my remote host through ssh port 22 using my laptop with ubuntu 20.04, I got this error. Even though, yesterday all are fine.
$ firstname.lastname@example.org -v OpenSSH_8.2p1 Ubuntu-4, OpenSSL 1.1.1f 31 Mar 2020 debug1: Reading configuration data /etc/ssh/ssh_config debug1: /etc/ssh/ssh_config line 19: include /etc/ssh/ssh_config.d/*.conf matched no files debug1: /etc/ssh/ssh_config line 21: Applying options for * debug1: Connecting to 10.1.1.1 [10.1.1.1] port 22. debug1: Connection established. debug1: identity file /home/mine/.ssh/id_rsa type 0 debug1: identity file /home/mine/.ssh/id_rsa-cert type -1 debug1: identity file /home/mine/.ssh/id_dsa type -1 debug1: identity file /home/mine/.ssh/id_dsa-cert type -1 debug1: identity file /home/mine/.ssh/id_ecdsa type -1 debug1: identity file /home/mine/.ssh/id_ecdsa-cert type -1 debug1: identity file /home/mine/.ssh/id_ecdsa_sk type -1 debug1: identity file /home/mine/.ssh/id_ecdsa_sk-cert type -1 debug1: identity file /home/mine/.ssh/id_ed25519 type -1 debug1: identity file /home/mine/.ssh/id_ed25519-cert type -1 debug1: identity file /home/mine/.ssh/id_ed25519_sk type -1 debug1: identity file /home/mine/.ssh/id_ed25519_sk-cert type -1 debug1: identity file /home/mine/.ssh/id_xmss type -1 debug1: identity file /home/mine/.ssh/id_xmss-cert type -1 debug1: Local version string SSH-2.0-OpenSSH_8.2p1 Ubuntu-4 debug1: Remote protocol version 2.0, remote software version OpenSSH_7.6p1 Ubuntu-4ubuntu0.3 debug1: match: OpenSSH_7.6p1 Ubuntu-4ubuntu0.3 pat OpenSSH_7.0*,OpenSSH_7.1*,OpenSSH_7.2*,OpenSSH_7.3*,OpenSSH_7.4*,OpenSSH_7.5*,OpenSSH_7.6*,OpenSSH_7.7* compat 0x04000002 debug1: Authenticating to 10.1.1.1:22 as 'mine' debug1: SSH2_MSG_KEXINIT sent debug1: SSH2_MSG_KEXINIT received debug1: kex: algorithm: curve25519-sha256 debug1: kex: host key algorithm: ecdsa-sha2-nistp256 debug1: kex: server->client cipher: email@example.com MAC: <implicit> compression: none debug1: kex: client->server cipher: firstname.lastname@example.org MAC: <implicit> compression: none debug1: expecting SSH2_MSG_KEX_ECDH_REPLY Connection reset by 10.1.1.1 port 22
However, when I tried to remote another host through another ssh port (i.e 2222), there is no problem. This only happen when I tried to remote via port 22. I am sure there is no firewall blocking. Because yesterday all are fine, I can remote that host through ssh port 22.
Furthermore, when I tried to remote that host (10.1.1.1) using another computer, there is fine, no error. So, maybe the problem is on my laptop, not on my remote host.