DNS service has the line: "system" ?

Hi,
I’ve started working on a Vyos machine, and under the DNS service, there is a line with the text “system”. it looks like this:
dns {
forwarding {
cache-size 150
listen-on …
name-server x.x.x.x
system
}
}

  1. Does anyone know what the “system” means?.
  2. Is cache-size of 150 is enough?. we are experiencing a problem lately where the Vyos can translate addresses (can’t ping www.google.com) suddenly. meaning, everything works great, and one day, in the middle of nowhere => walla, can’t ping addresses no more.

Would be happy to get your advise.
thank you.!

http://www.brocade.com/content/html/en/vrouter5600/35r3/vyatta-35r3-services/GUID-AD60EA33-7519-49CD-86F0-B07170726213.html

[quote]Name server locations can be obtained in three ways:

From the system name server list, defined by using the set system name-server command
By DHCP
By listing additional name servers by using the set service dns forwarding dhcp command
By default, the Vyatta system forwards DNS requests to name servers on the system name server list plus name servers obtained through DHCP. You can override the default behavior by specifying any or all of the following:

Specifically use system-defined name servers. To do this, use the set service dns forwarding system command.
Specifically use name servers received for the interface that is using DHCP client to get an IP. To do this, use the set service dns forwarding dhcp command.
List additional name servers by using the set service dns forwarding name-server command.
These three options can be used in any combination; however, using any of them eliminates the default DNS forwarding behavior.

When DNS forwarding starts or restarts, it broadcasts a message to all the name servers in the pool and selects the first name server to answer. This name server is used unless it becomes unreachable, in which case the system sends another broadcast message to the remaining name servers in the pool.[/quote]

Thank you for the detailed explenation. !