Disabling host key checking on LAN

[Nico Kadel-Garcia]

On Fri, Aug 28, 2015 at 8:48 AM, Bostjan Skufca <bostjan at a2o.si> wrote:
> On 27 August 2015 at 05:01, Damien Miller <djm at mindrot.org> wrote:
>> Yeah, it's unfortunately quite difficult to implement address matching
>> in ~/.ssh/config because of the interplay of Host matching, Hostname
>> directives, hostname canonicalisation*, proxy commands, hosts having
>> multiple addresses, IPv4/IPv6 and when the addresses are actually
>> resolved and available to the parser.
>>
>> I've not figured out a clean way to do it that isn't also complex and
>> probably fragile to implement.
>
> If we disregard the "complex and probably fragile" part, what is the
> "clean way" you are talking about?
> Do you have some sort of RFC written down somewhere?

The interplays between DNS and multiple formats for the same target
SSH server makes such an RFC a nightmare in outsmarting all the local
settings. In complex environments, I'm afraid that "known_hosts" is
often an active detriment to stable operation, especially because
there is *no* published tool for "scrub the old rejected line and
accept the new one*. It's most clear when a new server on the same IP
address replaces an old host but uses new SSH host keys.

In environments where critical server hostnames and IP addresses are
not tied to consistent SSH keys, I'm afraid there is little choice but
to discard the use of known_hosts.