Bug#221849: ClientAliveInterval option emits error to screen
I've seen similar behaviour when connecting to a sarge ssh server from
an RHEL client. Upgrading the client from:
OpenSSH_3.6.1p2, SSH protocols 1.5/2.0, OpenSSL 0x0090701f
OpenSSH_4.2p1, OpenSSL 0.9.7a Feb 19 2003
made the problem go away. With -v turned, on the newer ssh client emits
(at the same frequency as the old "no channel -1" message):
debug1: client_input_channel_req: channel 0 rtype firstname.lastname@example.org
without the "no channel" error message.
So it looks like this bug has been fixed upstream....