We have a quite old installation of SUSE LINUX 10.1 (i586) in the office.

The problem shortly: I can successfully ssh to it from machines in the same LAN (192.168.1.0) and not from others (that are in 10.23.0.0).

The SuSE has SSH server openssh-4.2p1-18.12. I have ruled out the firewall and hosts.allow and hosts.deny files.

When my ssh login attempt fails, here is what the logs say:

on the client:

$ ssh -vvv 192.168.1.5
OpenSSH_5.3p1, OpenSSL 1.0.1e-fips 11 Feb 2013
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Applying options for *
debug2: ssh_connect: needpriv 0
debug1: Connecting to 192.168.1.5 [192.168.1.5] port 22.
debug1: Connection established.
debug1: identity file /home/nbuild/.ssh/identity type -1
debug1: identity file /home/nbuild/.ssh/identity-cert type -1
debug1: identity file /home/nbuild/.ssh/id_rsa type -1
debug1: identity file /home/nbuild/.ssh/id_rsa-cert type -1
debug1: identity file /home/nbuild/.ssh/id_dsa type -1
debug1: identity file /home/nbuild/.ssh/id_dsa-cert type -1

on the server:

Aug 21 16:34:25 serverhost sshd[20736]: debug3: fd 4 is not O_NONBLOCK
Aug 21 16:34:25 serverhost sshd[20736]: debug1: Forked child 20739.
Aug 21 16:34:25 serverhost sshd[20736]: debug3: send_rexec_state: entering fd = 7 config len 403
Aug 21 16:34:25 serverhost sshd[20736]: debug3: ssh_msg_send: type 0
Aug 21 16:34:25 serverhost sshd[20736]: debug3: send_rexec_state: done
Aug 21 16:34:25 serverhost sshd[20739]: debug1: rexec start in 4 out 4 newsock 4 pipe 6 sock 7
Aug 21 16:34:25 serverhost sshd[20739]: debug1: inetd sockets after dupping: 3, 3
Aug 21 16:34:25 serverhost sshd[20739]: debug3: Normalising mapped IPv4 in IPv6 address
Aug 21 16:34:25 serverhost sshd[20739]: Connection from 10.23.1.11 port 44340

The above log on the server is when I enable DEBUG3 log level. However, with the default log level (INFO), the only thing the server logs is this:

Aug 21 16:38:32 serverhost sshd[20749]: Did not receive identification string from 10.23.1.11

Any hints? I feel I've tried everything already.