Bug#841531: openssh-client: no matching key exchange method found. Their offer: diffie-hellman-group1-sha1

[Martin-Éric Racine <martin-eric.racine@iki.fi>]

2016-10-21 14:40 GMT+03:00 Adam D. Barratt <adam@adam-barratt.org.uk>:
> On 2016-10-21 12:26, Martin-Éric Racine wrote:
>>
>> Unable to negotiate with 172.16.1.254 port 22: no matching key
>> exchange method found. Their offer: diffie-hellman-group1-sha1
>>
>> I get the above error when trying to connect to a router using
>> openssh-client from Testing.
>>
>> Connecting using the openssh-client from Stable works as expected.
>
>
> That's to be expected, given:
>
> openssh (1:7.1p1-1) unstable; urgency=medium
>
>   * New upstream release (http://www.openssh.com/txt/release-7.0, closes:
>     #785190):
>     - Support for the legacy SSH version 1 protocol is disabled by default
>       at compile time.
>     - Support for the 1024-bit diffie-hellman-group1-sha1 key exchange is
>       disabled by default at run-time.  It may be re-enabled using the
>       instructions at http://www.openssh.com/legacy.html

That would indeed explain it.

Exception added in .ssh/config for that subnet.

Thanks!
Martin-Éric