On an edge router, you want to create a default route with a next hop to an external connection. The route should be available only when you are receiving routes from the external provider.
Which type of route would you configure on your device to accomplish this objective?
A.
an aggregate route
B.
a generated route
C.
a primary contributing route
D.
a static route
Explanation:
Configuring Generated Route Options
In the defaults and route parts of the generate statement, you can specify options that define additional information about generated routes that is included with the route when it is installed in the routing table. All generated options are optional. Generated options that you specify in the defaults part of the generate statement are treated as global defaults and apply to all the generated routes you configure in the generate statement. Generated options that you specify in the route part of the generate statement override any global generated options and apply to that destination only.To configure generated route options, include one or more of them in the defaults or route part of the generate statement (for routing instances, include the statement).
[edit]
routing-options
generate {
(defaults | route) {
(active | passive);
as-path <as-path> <origin (egp | igp | incomplete)> <atomic-aggregate> <aggregator as-number in-address>;
community [ community-ids ];
discard;
(brief | full);
(metric | metric2 | metric3 | metric4) metric <type type>;
(preference | preference2 | color | color2) preference <type type>;
tag string;
}
}
}For a list of hierarchy levels at which you can include this statement, see the statement summary section for this statement.
The following sections explain how to configure generated route options:Understanding Conditionally Generated Routes
Generated routes are used as the route of last resort. A packet is forwarded to the route of last resort when the routing tables have no information about how to reach that packets destination. One use of route generation is to generate a default route to use if the routing table contains a route from a peer on a neighboring backbone.
A generated route becomes active when it has one or more contributing routes. A contributing route is an active route that is a more specific match for the generated destination. For example, for the destination 128.100.0.0/16, routes to 128.100.192.0/19 and 128.100.67.0/24 are contributing routes, but routes to 128.0.0.0./8, 128.0.0.0/16, and 128.100.0.0/16 are not.
A route can contribute only to a single generated route. However, an active generated route can recursively contribute to a less specific matching generated route. For example, a generated route to the destination 128.100.0.0/16 can contribute to a generated route to 128.96.0.0/13.
By default, when generated routes are installed in the routing table, the next hop is chosen from the primary contributing route.
Note: You can configure only one generated route for each destination prefix.
To configure generated routes in the default routing table (inet.0), include the generate statement:
generate {(defaults | route destination ) {(active | passive);as-path <as-path> <origin (egp | igp | incomplete)> <atomic-aggregate> <aggregator as-number in-address>;community [ community-ids ];discard;(brief | full);(metric | metric2 | metric3 | metric4) metric <type type>;policy policy-name;(preference | preference2 | color | color2) preference <type type>;tag string;}}
Note: You cannot configure generated routes for the IPv4 multicast routing table (inet.1) or the IPv6 multicast routing table (inet6.1).
The generate statement consists of two parts:
* defaultsHere you specify global generated route options. These are treated as global defaults and apply to all the generated routes you configure in the generate statement. This part of the generate statement is optional.
* routeHere you configure individual generated routes. In this part of the generate statement, you optionally can configure generated route options. These options apply to the individual destination only and override any options you configured in the defaults part of the generate statement.