Vyatta Network OS Documentation

Learn how to install, configure and operate the Vyatta NOS, which helps drive our virtual networking & physical platforms portfolio.

Path monitor state tracking on routes required by that monitor

Suppose that you configure a static route to track the status of a monitor/policy pair, and that route is required for the associated monitor to reach it's target; if the monitor/policy pair ever becomes non-compliant then the route will be removed from the FIB and the monitor will never recover (triggering the route to be re-installed) since it no longer has a route to reach its target.

For example, suppose you have a monitor targeting

$ set service path-monitor host DC target
$ set service path-monitor monitor DC type ping host DC

If you have only one static route to reach, and you associate the DC monitor with it, the route will be withdrawn and the monitor will never recover should a non-compliant state ever be reached.

$ show ip route
Routing entry for
  Known via "static", distance 1, metric 0, tag 0, best
  * via, dp0p1s1
Ensure that there is always an available route for the monitor.
set protocols static route next-hop path-monitor monitor DC policy 'DC'
set protocols static route next-hop distance 10
set protocols static route next-hop distance 20
set protocols static route next-hop interface 'dp0p1s1'
We have a default static route with two next hops. The distances ensure that is the preferred next hop so long as the DC monitor is in compliance with the DC policy. The next hop will be used if this ever changes. The /32 static route ensures that the monitor always has a route to its target via, even if the default route is withdrawn.