Connection broken by firewall with a pass all rule

[pierre1]

Hi All,
       I am working to setup a firewall and I get
a problem very strange and annoying. I have added
a pass all rule on the igb0 and during the ssh connection
the connection is broken. Not immediately however but after few
seconds.

The destination machine is very old and behind an other router. It is possible
that the ssh protocol used is old (about 10 years) and strange for a modern
firewall. However, when the route to the machine goes directly by the router
at the entry of the network  containing the destination machine
(without going by the default OpnSense
router) everything is OK.

In attachment you will find two screenshots showing the problem. Ideally,
I would be able to relax the rules as much as I want (even to remove
almost all rules except the mandatory one like the rules used for Nat).

Do you have some ideas on how to solve this problem?

Thanks a lot for your help,

Best regards

[bartjsmit]

On the client use ssh -v for verbose output. Consider telnet for a host that old. SSH may not add much security.

Bart...