SR OS route policy statements consist of a sequence of ordered rules, or entries. When the policy is applied to a routing adjacency, route table, or some other context, then each route associated with that context is evaluated by the rules of the policy, in the specified order, until a matching entry is found or the end of the policy is reached. If a matching entry is found, then its actions are applied to the route. However, if there is no matching entry, then the policy default-action is applied to the route.
Some of the match criteria that can be used in a policy entry include:
IP prefix-list reference
AS path regular expression
community list reference
route properties such as MED, local-preference, IGP metric, IGP route type, BGP path type, and so on
In classic mode and mixed-mode every policy-statement must have numbered entries.
In full Model-Driven mode, each policy-statement can be configured to be entry-type named or entry-type numbered. Numbered types behave as in classic mode and mixed-mode. In named types, each entry is a specific string-format name up to 255 characters in length, and entries are evaluated in user order (the order they appear in the configuration). MD-CLI and NETCONF management interfaces support insert commands that change the order of the named entries in a policy statement. For example, in the MD-CLI configuration context of a policy-statement X, if a named-entry entry2 needs to be moved so that it is evaluated immediately before an existing named-entry entry1 this can be achieved using the insert named-entry entry2 before entry1 command.