how frequently ok to run script (run only on event?)

RouterOS Scripting
1

G’day,

So as I understand it there is no way to run a particular script on any type of event (other than using say the LOG watching script).

example - ospf primary gateway goes down, every router switches to route 2.. However - they need to switch DNS servers when this happens.. I’ve found no better way than to just run the following script every 10 seconds or so.

# Watch for MAIN route up (10.0.1.1) if it is up keep DNS
# if it's down - we will be going out alternate ISP so then use
# google DNS 8.8.8.8 and 8.8.4.4

# Begin Configuration
:local secondaryDNSServers "8.8.8.8,8.8.4.4"
:local primaryDNSServers "10.0.1.1"


# End Configuration

:local curGateway
:local curDNS

:set $curGateway [/ip route find gateway=10.0.1.1 dst-address=0.0.0.0/0]
#:log info "curGateway=$curGateway"

# Now compared curGateway with current DNS to see if it is matched up

# Get list of current DNS servers and put into variable
#
# mangle DNS server list into format acceptable for the
# ip dns set command
#

:foreach srv in=[/ip dns get servers] do={
    :if ( [:len $curDNS] = 0 ) do={
        :set $curDNS $srv
    } else={
        :set $curDNS ( $curDNS . "," . $srv )
    }
}


# See if curGateway returned any results - if it DID NOT.. then we know we
# are NOT using our primary gateway. In which case switch DNS to public
# google DNS servers
:if ( $curGateway = "" ) do={
#    :log info "curGateway != true; curDNS=$curDNS, primaryDNS=$secondaryDNSServers"
    :if ( $curDNS != $secondaryDNSServers ) do {
        /ip dns set servers $secondaryDNSServers 
        /ip dns cache flush
        :log info "PRIMARY INTERNET DOWN, set DNS servers to Google's Public DNS $pubServers"
    }
} else={
#    :log info "curGateway == true; curDNS=$curDNS, primaryDNS=$primaryDNSServers"
    :if ( $curDNS != $primaryDNSServers ) do={
        /ip dns set servers $primaryDNSServers 
        /ip dns cache flush
        :log info "PRIMARY INTERNET UP,  set DNS servers to $primaryDNSServers"
    }
}

Is it bad form - to run a script every 10 seconds.. just seems so darn inefficient when 99% of the time it will do nothing.. would be MUCH better to run when the OSPF event happens…

Is this just way it is and deal with it?

cheers,
Paul

2

If the script is able to finish before the new run starts, there is nothing against running it so frequently.