openssh unix dev - Sep 2015 - OpenSSH Always Hangs When Connecting to Remote

I am running Arch Linux. Very updated version. When I try to connect to
remote servers using OpenSSH I get a hang as show here:

$ ssh -v compsci at 10.1.1.12
OpenSSH_7.1p1, OpenSSL 1.0.2d 9 Jul 2015
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Connecting to 10.1.1.12 [10.1.1.12] port 22.
debug1: Connection established.
debug1: identity file /home/carloabelli/.ssh/id_rsa type 1
debug1: key_load_public: No such file or directory
debug1: identity file /home/carloabelli/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/carloabelli/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/carloabelli/.ssh/id_dsa-cert type -1
debug1: identity file /home/carloabelli/.ssh/id_ecdsa type 3
debug1: key_load_public: No such file or directory
debug1: identity file /home/carloabelli/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/carloabelli/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/carloabelli/.ssh/id_ed25519-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.1
debug1: Remote protocol version 2.0, remote software version OpenSSH_6.2
debug1: match: OpenSSH_6.2 pat OpenSSH* compat 0x04000000
debug1: Authenticating to 10.1.1.12:22 as 'compsci'
debug1: SSH2_MSG_KEXINIT sent

or here:

$ ssh -v thebes.openshells.net
OpenSSH_7.1p1, OpenSSL 1.0.2d 9 Jul 2015
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Connecting to thebes.openshells.net [23.239.220.55] port 22.

I believe this is an OpenSSH issue as dropbear works fine:

$ dbclient compsci at 10.1.1.12
Last login: Sat Sep 19 00:34:39 2015 from 10.11.1.253
compsci-server:~ compsci$

I have been struggling with this one. Any thoughts?

Thanks,
Carlo

On Sep 20, 2015 2:08 AM, "Carlo Abelli" <carlo.abelli at
gmail.com> wrote:
...
> debug1: SSH2_MSG_KEXINIT sent
I suspect a path mtu problem.  The key exchange packet is one of the first
large ones in an SSH connection so it tends to show up such problems.

See http://www.snailbook.com/faq/mtu-mismatch.auto.html
> I believe this is an OpenSSH issue as dropbear works fine:
Dropbear supports a much smaller number of key exchange methods (exactly
one in older versions) so its packets are much smaller than openssh's.

On 09/20/2015 03:25 AM, Darren Tucker wrote:
> I suspect a path mtu problem.  The key exchange packet is one of the
> first large ones in an SSH connection so it tends to show up such problems.
>
> Seehttp://www.snailbook.com/faq/mtu-mismatch.auto.html
> <http://www.snailbook.com/faq/mtu-mismatch.auto.html>
Has this been changed? SSH used to work fine on my old machine. My local
mtu and server mtu are higher than required. Therefore the only thing I
could expect would be a lower mtu on the vpn. Has this changed in recent
versions. As previously I was using OSX I expect the OpenSSH version was
older. Still strange to me that it worked before and not now. I will
test tomorrow to see if connecting on the actual network solves the issue.