Summary of Routing Policy Actions

An action is what the policy framework software does if a route matches all criteria defined in a match condition. You can configure one or more actions in a term.

The policy framework software supports the following types of actions:

Flow control actions, which affect whether to accept or reject the route or whether to evaluate the next term or routing policy
Actions that manipulate route characteristics
Trace action, which logs route matches

Manipulating the route characteristics allows you to control which route is selected as the active route to reach a destination. In general, the active route is also advertised to a routing platform’s neighbors. You can manipulate the following route characteristics: AS path, class, color, community, damping parameters, destination class, external type, next hop, load balance, local preference, metric, origin, preference, and tag.

For the numeric information (color, local preference, metric, preference, and tag), you can set a specific value or change the value by adding or subtracting a specified amount. The addition and subtraction operations do not allow the value to exceed a maximum value and drop below a minimum value.

All policies have default actions in case one of the following situations arises during policy evaluation:

A policy does not specify a match condition.
A match occurs, but a policy does not specify an action.
A match does not occur with a term in a policy and subsequent terms in the same policy exist.
A match does not occur by the end of a policy.

An action defines what the router does with the route when the route matches all the match conditions in the from and to statements for a particular term. If a term does not have from and to statements, all routes are considered to match and the actions apply to all routes.

Each term can have one or more of the following types of actions. The actions are configured under the then statement.

Flow control actions, which affect whether to accept or reject the route and whether to evaluate the next term or routing policy
Actions that manipulate route characteristics
Trace action, which logs route matches

If you do not specify an action, one of the following results occurs:

The next term in the routing policy, if one exists, is evaluated.
If the routing policy has no more terms, the next routing policy, if one exists, is evaluated.
If there are no more terms or routing policies, the accept or reject action specified by the default policy is executed.

Table 1 summarizes the routing policy actions.

Table 1: Summary of Key Routing Policy Actions
Action	Description
Flow Control Actions	These actions control the flow of routing information into and out of the routing table.
`accept`	Accepts the route and propagates it. After a route is accepted, no other terms in the routing policy and no other routing policies are evaluated.
`reject`	Rejects the route and does not propagate it. After a route is rejected, no other terms in the routing policy and no other routing policies are evaluated.
`next term`	Skips to and evaluates the next term in the same routing policy. Any `accept` or `reject` action specified in the `then` statement is ignored. Any actions specified in the `then` statement that manipulate route characteristics are applied to the route.
`next policy`	Skips to and evaluates the next routing policy. Any `accept` or `reject` action specified in the `then` statement is ignored. Any actions specified in the `then` statement that manipulate route characteristics are applied to the route.
Route Manipulation Actions	These actions manipulate the route characteristics.
`as-path-prepend as-path`	Appends one or more AS numbers at the beginning of the AS path. If you are specifying more than one AS number, include the numbers in quotation marks. The AS numbers are added after the local AS number has been added to the path. This action adds AS numbers to AS sequences only, not to AS sets. If the existing AS path begins with a confederation sequence or set, the appended AS numbers are placed within a confederation sequence. Otherwise, the appended AS numbers are placed with a nonconfederation sequence.
`as-path-expand last-as count n`	Extracts the last AS number in the existing AS path and appends that AS number to the beginning of the AS path `n` times. Replace `n` with a number from `1` through `32`. The AS numbers are added after the local AS number has been added to the path. This action adds AS numbers to AS sequences only, not to AS sets. If the existing AS path begins with a confederation sequence or set, the appended AS numbers are placed within a confederation sequence. Otherwise, the appended AS numbers are placed with a nonconfederation sequence.
`class class-name`	Applies the specified class-of-service (CoS) parameters to routes installed into the routing table.
`color preference` `color2 preference`	Sets the preference value to the specified value. The `color` and `color2` preference values can be a number from `0` through `4,294,967,295` (`2³² – 1`). A lower number indicates a more preferred route.
`damping name`	Applies the specified route-damping parameters to the route. These parameters override BGP's default damping parameters. This action is useful only in import policies.
`local-preference value`	Sets the BGP local preference attribute. The preference can be a number from `0` through `4,294,967,295` (`2³² – 1`).
`metric metric` `metric2 metric` `metric3 metric` `metric4 metric`	Sets the metric. You can specify up to four metric values, starting with `metric` (for the first metric value) and continuing with `metric2`, `metric3`, and `metric4`. For BGP routes, `metric` corresponds to the MED, and `metric2` corresponds to the IGP metric if the BGP next hop loops through another router.
`next-hop address`	Sets the next hop. If you specify `address` as `self`, the next-hop address is replaced by one of the local router's addresses. The advertising protocol determines which address to use.

Summary of Routing Policy Actions

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