The problem: The key exchange between putty (Win7) and the linux ssh server takes about 10 seconds. Prior to moving my network to a new location, this didn't occur. I'm connecting to 3 different boxes all running debian distros. The versions range from 8.0 (jessie) to 9.5 (stretch).
The delay happens before any username or password prompts. I usually use private key authentication, but even when pageant is turned off, it makes no difference as the delay occurs before any authentication takes place.
All 3 have the same delay during initial key exchange. The log output for one of them is below. All 3 servers hang at the exact same spot, and give the same message about having other keys but PuTTY doesn't recognize them. See the time just before and just after: "Event Log: Server also has ecdsa-sha2-nistp256/ssh-dss/ssh-rsa host keys, but we don't know any of them"
=~=~=~=~=~=~=~=~=~=~=~= PuTTY log 2018.08.11 09:23:10 =~=~=~=~=~=~=~=~=~=~=~=
Event Log: Writing new session log (SSH raw data mode) to file: D:\tmp\putty.log
Event Log: Connecting to 192.168.1.242 port 22
Event Log: We claim version: SSH-2.0-PuTTY_Release_0.70
Incoming raw data at 2018-08-11 09:23:10
Event Log: Server version: SSH-2.0-OpenSSH_6.7p1 Raspbian-5+deb8u3
Event Log: Using SSH protocol version 2
Outgoing packet #0x0, type 20 / 0x14 (SSH2_MSG_KEXINIT)
Outgoing raw data at 2018-08-11 09:23:10
Incoming raw data at 2018-08-11 09:23:10 ........
Incoming packet #0x0, type 20 / 0x14 (SSH2_MSG_KEXINIT)
Event Log: Doing Diffie-Hellman group exchange
Outgoing packet #0x1, type 34 / 0x22 (SSH2_MSG_KEX_DH_GEX_REQUEST)
Outgoing raw data at 2018-08-11 09:23:10 .......
Incoming raw data at 2018-08-11 09:23:10 ........
Incoming packet #0x1, type 31 / 0x1f (SSH2_MSG_KEX_DH_GEX_GROUP)
Event Log: Doing Diffie-Hellman key exchange with hash SHA-256
Outgoing packet #0x2, type 32 / 0x20 (SSH2_MSG_KEX_DH_GEX_INIT) .....
Outgoing raw data at 2018-08-11 09:23:10
Incoming raw data at 2018-08-11 09:23:10
Incoming packet #0x2, type 33 / 0x21 (SSH2_MSG_KEX_DH_GEX_REPLY) ...
Event Log: Server also has ecdsa-sha2-nistp256/ssh-dss/ssh-rsa host keys, but we don't know any of them
Event Log: Host key fingerprint is:
Event Log: ssh-ed25519 256 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Outgoing packet #0x3, type 21 / 0x15 (SSH2_MSG_NEWKEYS)
Outgoing raw data at 2018-08-11 09:23:23
Event Log: Initialised AES-256 SDCTR client->server encryption
Event Log: Initialised HMAC-SHA-256 client->server MAC algorithm
Outgoing raw data at 2018-08-11 09:23:23
Incoming packet #0x3, type 21 / 0x15 (SSH2_MSG_NEWKEYS)
Event Log: Initialised AES-256 SDCTR server->client encryption
Event Log: Initialised HMAC-SHA-256 server->client MAC algorithm
Outgoing packet #0x4, type 5 / 0x05 (SSH2_MSG_SERVICE_REQUEST)
I've gone through all the other suggestions for ssh delays: disabling reverse dns lookups, fixing any dns problems, disabling GSSAPIAuthentication. I've tried at least 1/2 dozen other fixes from various threads on various forums. None of them effect this in any way.
Edit: I added openssh to my cygwin and I can ssh into these boxes from cygwin with no delay.
