Compact way of having the same public key for many server ids in ssh known_hosts

Question

The known_hosts file has entries in the format of:

{server-id} {signature-algorithm} {public-key-string} {comment}

I work with the system that has many machines that share the same {public-key-string} but have many, almost 7000, different {server-ids}, I was wondering is it possible to make entries more compact?

I know I could specify all of them comma-separated like:

{server-id1},{server-id2},... {signature-algorithm} {public-key-string} {comment}

but there are almost 7000 of such {server-ids} with their IPs and aliases.

The naming schema of {server-ids} is something like:

a01b01c01d01
a01b01c01d02
...
a01b01c02d01
...
a08b11c06d12

Is some compact syntax for known_hosts available? Such as:

a[01-08]b[01-11]c[01-06]d[01-12] {signature-algorithm} {public-key-string} {comment}

Can someone tell me how to achieve this?

Answer 1

Once I submitted the question, I noticed that there is an entry on a similar file (ssh_known_hosts) file in the manual of sshd.

man sshd

The manual states:

Hostnames is a comma-separated list of patterns (‘*’ and ‘?’ act as wildcards); each pattern in turn is matched against the canonical host name (when authenticating a client) or against the user-supplied name (when authenticating a server). A pattern may also be preceded by ‘!’ to indicate negation: if the host name matches a negated pattern, it is not accepted (by that line) even if it matched another pattern on the line. A hostname or address may optionally be enclosed within ‘[’ and ‘]’ brackets then followed by ‘:’ and a non-standard port number.

Since the file format of ssh_known_hosts matches known_hosts, the answer to my question is by using wildcards:

a0?b??c0?d??,192.168.*.* {signature-algorithm} {public-key-string} {comment}

However, this still does not restrict only values I wanted to have, therefore if someone knows how to restrict it further please let me know.

a0?b??c0?d?? can also be a0ibx3c0wdxy