Host Restricts the following declarations (up to the next Host key‐ word) to be only for those hosts that match one of the patterns given after the keyword. If more than one pattern is provided, they should be separated by whitespace.
HostName Specifies the real host name to log into. This can be used to specify nicknames or abbreviations for hosts. If the hostname contains the character sequence ‘%h’, then this will be replaced with the host name specified on the commandline (this is useful for manipulating unqualified names).
Host X01 HostName X01.YYY.com Host X02 HostName X02.YYY.com ... Host X01 X02 ... User my_username Compression yes
Host *.co.uk The following pattern would match any host in the 192.168.0.[0-9] network range: Host 192.168.0.? A pattern-list is a comma-separated list of patterns. Patterns within pattern-lists may be negated by preceding them with an exclamation mark (‘!’). For example, to allow a key to be used from anywhere within an organisation except from the “dialup” pool, the following entry (in authorized_keys) could be used: from="!*.dialup.example.com,*.example.com"