VyOS versions before 1.4.0 didn't have any restrictions on syslog host node names. That had two unplanned effects:

• It allowed people to use node names like 192.0.2.1:9000 to specify the remote port, when we had no official syntax for that.
• It allowed people to send log messages of different facilities and levels to different ports of the same remote server.

This configuration used to be valid and working but it is completely impossible to replicate now:

system {
 syslog {
     host 192.0.2.1 {
         facility all {
             level "info"
         }
     }
     host 192.0.2.1:9000 {
         facility auth {
             level "info"
         }
     }
     host 192.0.2.1:9001 {
         facility kern {
             level "info"
         }
     }
}

We could solve that by making the node name meaningless and adding an explicit address option. Not sure if there are lighter options.

set system syslog remote SomeServer address 192.0.2.1
set system syslog remote SomeServer port 9001