FYI Incompatibilities between recent versions of OpenSSH and Sun SSH

Clark, Bill W. Bill.Clark at
Sat Jan 17 04:47:48 EST 2004

These problem aren't bugs per se but rather major version differences.
Sun has finally published a FAQ on their SSH two days ago
=sshd   The problem is rooted in the fact that Sun developed their SSH
based on OpenSSH 2.5.1p1  That version came out in February of 2001.
There have been a number of changes since then and that has caused
timeout problems in past for uses when interacting from Solaris 9 to
other systems that are running OpenSSH.  
We have observed session ending abruptly after 15 minutes even when
actively using the session.  Also we have seen automated SSH file
transfers hang.
Sun has released one patch for their version of SSH, but it does not
address this issue.
Patch-ID# 113273-04 

Here is a little matrix where problems occur.  Haven't done the test
with 3.7.1 yet as we assume the same problem will exist as it is based
on the fact that Sun is using 2.5.1 code.

	Here is a little matrix:

	Disconnect Problem		Client		Server
	------------------------------	----------
	No                                      Putty
OpenSSH 3.5
	No                                      Putty
SunSSH 1.0
	No                                      SecureCRT       OpenSSH
	No                                      SecureCRT       SunSSH
	No				OpenSSH 3.5	OpenSSH 3.5
	No				OpenSSH 3.5	SunSSH 1.0
	No				SunSSH 1.0	SunSSH 1.0
	Yes				SunSSH 1.0	OpenSSH 3.5

	Looks like Sun doesn't understand the following definitions:
	ClientAliveInterval	30
	ClientCountMax		30

	That would normally disconnect you after 15 minutes of
inactivity.  It times out after 15 minutes of activity or inactivity.

	What I recommend is Stop using Sun SSH or changing all the
OpenSSH servers to have the following definitions:

	ClientAliveInterval	1800
	ClientCountMax		3

Bill W. Clark

PGP ID: 0xC8447EB1

SMTP:bill.clark at

More information about the openssh-unix-dev mailing list