Connection stalls at debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP

Darren Tucker dtucker at
Tue Feb 10 06:28:48 AEDT 2015

On Mon, Feb 9, 2015 at 2:23 PM, Petr Lautrbach <plautrba at> wrote:

> [...]
> It seems to be the same problem as described and discussed in this [1]
> thread.  MTU 1400 is not enough for packet sent by
> openssh-6.6.1p1-11.1.fc21 with default settings. The size of one of
> initial packets could be even 1968. Your VPN probably makes a
> fragmentation but doesn't do the correct defragmentation. As a
> workaround you can set shorter lists of MACs used by your client, eg:

I wrote an FAQ entry for this a long time ago:

I'd add "if you run netstat on both ends and see "SendQ" non-zero and not
decreasing then this is likely your problem.

I should add this to the faq....

Darren Tucker (dtucker at
GPG key 8FF4FA69 / D9A3 86E9 7EEE AF4B B2D4  37C9 C982 80C7 8FF4 FA69
    Good judgement comes with experience. Unfortunately, the experience
usually comes from bad judgement.

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