Redirect policies

SR OS-based routers support configuring of IPv4 and IPv6 redirect policies. Redirect policies allow specifying multiple redirect target destinations and defining status check test methods used to validate the ability for a destination to receive redirected traffic. This destination monitoring allows routers to react to target destination failures. To specify an IPv4 redirect policy, define all destinations to be IPv4. To specify an IPv6 redirect policy, define all destinations to be IPv6. IPv4 redirect policies can only be deployed in IPv4 filter policies. IPv6 redirect policy can only be deployed in IPv6 filter policies.

Redirect policies support the following destination tests:

• ping test with configurable interval, drop-count, and time-out

• unicast-rt-test for unicast routing reachability, supported only when router instance is configured for a specific redirect policy. The test yields true if the route to the specified destination exists in RTM for the configured router instance.

Each destination is assigned an initial or base priority describing this destination’s relative importance within the policy. The destination with the highest priority value is selected as most-preferred destination and programmed on line cards in filter policies using this redirect policy as an action. Only destinations that are not disabled by the programmed test (if configured) are considered when selecting the most-preferred destination.

In some deployments, it may not be necessary to switch from a currently active, most-preferred redirect-policy destination when a new more-preferred destination becomes available. To support such deployments, operators can enable the sticky destination functionality (config>filter>redirect-policy>sticky-dest). When enabled, the currently active destination remains active unless it goes down or an operator forces the switch using the tools>perform>filter>redirect-policy>activate-best-dest command. An optional sticky destination hold-time-up is available to delay programming the sticky destination in the redirect policy (transition from action forward to PBR action to the most-preferred destination). When the timer is enabled, the first destination that comes up is not programmed and instead the timer is started. After the timer expires, the most-preferred destination at that time is programmed (which may be a different destination from the one that started the timer). Note the following:

• When the manual switchover to most-preferred destination is executed as described above, the hold-time-up is stopped.

• When the timer value is changed, the new value takes immediate effect and the timer is restarted with the new value (or expired if no-hold-time-up is configured).

Feature restrictions:

• Redirect policy is supported for ingress IPv4 and IPv6 filter policies only.

• Different platforms support different scale for redirect policies. Contact your local Nokia representative to ensure the planned deployment does not exceed recommended scale.