I'm having trouble connecting to desktop1
(see figure below) from server
(red arrow in figure) with ssh. It always says:
ssh_exchange_identification: Connection closed by remote host
I don't have problem connecting to the server from desktop1
or desktop2
, nor do I have any problem connecting to desktop2
from server
, or connecting from desktop1
to desktop2
and vice versa.
I tried to troubleshoot the problem by creating a temporary sshd server on desktop1
as follows:
[desktop1]# $(which sshd) -Ddddp 4000
and to connect to it from server
:
[server]# ssh -v -p 4000 root@desktop1
OpenSSH_7.1p2, OpenSSL 1.0.2g-fips 1 Mar 2016
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 56: Applying options for *
debug1: Executing proxy command: exec /usr/bin/sss_ssh_knownhostsproxy -p 4000 desktop1
debug1: permanently_set_uid: 0/0
debug1: permanently_drop_suid: 0
debug1: identity file /root/.ssh/id_rsa type 1
debug1: key_load_public: No such file or directory
debug1: identity file /root/.ssh/id_rsa-cert type -1
debug1: identity file /root/.ssh/id_dsa type 2
debug1: key_load_public: No such file or directory
debug1: identity file /root/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /root/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /root/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /root/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file /root/.ssh/id_ed25519-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.1
ssh_exchange_identification: Connection closed by remote host
#
which does not work.
But from desktop2
, the connection works fine:
[desktop2]# ssh -v -p 4000 root@desktop1
OpenSSH_7.1p2, OpenSSL 1.0.2g-fips 1 Mar 2016
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 56: Applying options for *
debug1: Executing proxy command: exec /usr/bin/sss_ssh_knownhostsproxy -p 4000 desktop1
debug1: permanently_set_uid: 0/0
debug1: SSH2_MSG_KEXINIT received
debug1: kex: server->client [email protected] <implicit> none
debug1: kex: client->server [email protected] <implicit> none
debug1: kex: [email protected] need=64 dh_need=64
debug1: kex: [email protected] need=64 dh_need=64
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
[...]
debug1: Sending environment.
debug1: Sending env LANG = en_US.UTF-8
Last login: Mon Mar 7 15:24:05 2016 from 10.0.21.200
Environment:
LANG=en_US.UTF-8
USER=root
LOGNAME=root
HOME=/root
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin
MAIL=/var/mail/root
SHELL=/bin/bash
SSH_CLIENT=10.0.21.200 39150 4000
SSH_CONNECTION=10.0.21.200 39150 10.0.21.204 4000
SSH_TTY=/dev/pts/1
TERM=xterm-256color
DISPLAY=localhost:11.0
Running /usr/bin/xauth remove unix:11.0
/usr/bin/xauth add unix:11.0 MIT-MAGIC-COOKIE-1 2843404fd74f1294efce8c6bb786fd75
File /etc/ssh/sshd_config
is the same on desktop1
and desktop2
.
The public/private keys of root are the same on server
, desktop1
and desktop2
.
Permissions are OK on all 3 machines and look like this:
# ll .ssh/
total 24
-rw------- 1 root root 1883 Nov 6 09:33 authorized_keys
-rw-------. 1 root root 668 Jan 26 2015 id_dsa
-rw-r--r--. 1 root root 620 Jan 26 2015 id_dsa.pub
-rw-------. 1 root root 887 Jan 26 2015 id_rsa
-rw-r--r--. 1 root root 240 Jan 26 2015 id_rsa.pub
-rw-r--r--. 1 root root 1893 Nov 5 10:31 known_hosts
Traceroute finds both desktops from server
:
[server]# traceroute -T -p 22 desktop1
traceroute to desktop1 (10.0.21.204), 30 hops max, 60 byte packets
1 gateway (10.0.21.30) 0.704 ms 0.874 ms 1.041 ms
2 desktop1 (10.0.21.204) 0.325 ms 0.438 ms 0.407 m
[server]#
[server]# traceroute -T -p 22 desktop1
traceroute to desktop2 (10.0.21.200), 30 hops max, 60 byte packets
1 gateway (10.0.21.30) 0.847 ms 0.985 ms 1.158 ms
2 desktop2 (10.0.21.200) 0.286 ms 0.310 ms 0.314 ms
So, what can be the cause of this ID exchange problem: ssh_exchange_identification: Connection closed by remote host
?
Thank you for your help.
Regards, Fuji.
desktop1
int/etc/hosts.allow
and/etc/hosts.deny
? What can you get from logs on the server?iptables
enabled on Desktop1 ? if yes, is it allowing ssh from the server's network ?