modem replaced, inbound 'ssh' now fails - Time Warner Internet

This question is about "modem replaced, inbound 'ssh' now fails", with Time Warner Cable internet and apps. I'm doing remote support for a consultant in a nearby (100 miles) city. I've been using ssh & tunnels to get into his network for years. Last week he had the cable modem replaced with a new 'Technicolor TC8717T'. The FE said it was configured to match the old one. Except that my ssh connection now will not complete.

ssh -v <IP address> shows:


debug1: Connection established


debug1: Local version string SSH-2.0-OpenSSH_7.6

and there it will hang indefinitely. I made a road trip yesterday to resolve this - no luck.

The modem has all firewall options disabled, traffic passes into an old Linksys firewall, this has port 22 forwarded to an internal Linux server. At this server, I run a 'strace' on the ssh daemon and see the inbound connection, the inbound version string, and the daemon returning its version string. This should then move to the authentication phase and send "login". But the client session never receives the server version string.

We reported this problem during the initial modem replacement visit, FE was not comprehending the problem. The next day, we called in again, got another FE visit, he replaced the new modem twice. Problem persists. I had my buddy run a port scan from - this reports port 22 as open.

Could there be some setting in this specific Technicolor modem that is partially blocking this ssh connection ?? Is there some way to get a tier 2 technician on the phone who understands the basic functionality of ssh ??


don m.

modem replaced, inbound 'ssh' now fails?