Understanding Routing Policy Processing

AC

Routing policy is a set of conditions and actions that are used to control the flow of routing updates and manipulate the routing table. Routing policy processing in Junos OS involves evaluating policies against routing updates and then taking actions based on the match results.

The following are the two true statements regarding routing policy processing:

A. The Junos OS verifies the match criteria of each policy in order and performs the associated action when a match occurs.

When a routing update is received, Junos OS evaluates the policies configured on the device against the update to see if there is a match. The policies are checked in order, and the first policy that matches the update is applied. The policy can have multiple conditions, and all of the conditions must be met for a match to occur. When a match occurs, the associated action is performed, and the policy processing for that update stops.

B. Policies are evaluated from right to left as displayed in the Junos OS configuration file.

In Junos OS, policies are evaluated from top to bottom, and from left to right within each term of the policy. Therefore, the policy at the top of the configuration file is evaluated first, followed by the one below it, and so on. Within each policy term, the conditions are evaluated from left to right. However, the right-to-left evaluation is incorrect.

C. Polices are evaluated based on the order in which they are applied to a routing protocol.

Routing policies are applied to routing protocols in a particular order, which determines the order in which the policies are evaluated. The order can be determined by the policy name or the order in which the policies are applied to the routing protocol. The policy applied first is evaluated first, followed by the second policy, and so on.

D. Policy processing stops once the last statement in the policy is evaluated.

When a routing update is processed against a policy, Junos OS evaluates each term of the policy until a match is found or all the terms are evaluated. If a match is found, the associated action is performed, and policy processing for that update stops. However, if no match is found, the update is processed against the next policy until a match is found, or all policies have been evaluated.

In conclusion, options A and B are the two true statements regarding routing policy processing in Junos OS. Option C is incorrect because the order of policy evaluation is determined by the order in which they are applied to the routing protocol, not the policy name. Option D is incorrect because policy processing continues until a match is found or all policies have been evaluated.