 | Copyright © 2008, Juniper Networks, Inc. All rights reserved. Trademark Notice. | |
You can group the routers in a single autonomous system (AS) into areas to reduce the amount of link-state advertisement (LSA) traffic on the network and to reduce the size of the topological databases that OSPF routers must maintain. If you do this, the AS must contain a single backbone area and optionally can contain any number of nonbackbone areas. The routers that make up the backbone must be physically contiguous. If they are not, you must configure virtual links to create the appearance of connectivity. You also can configure stub areas, which are areas through which AS external advertisements are not flooded, and not-so-stubby areas (NSSAs), which allow external routes to be flooded within an area.
The JUNOS software supports active backbone detection. Active backbone detection is implemented to verify that area border routers are connected to the backbone. If the connection to the backbone area is lost, then the router’s default metric is not advertised, effectively rerouting traffic through another area border router with a valid connection to the backbone.
Active backbone detection enables transit through an area border router with no active backbone connection. An area border router advertises to other routers that it is an area border router even if the connection to the backbone is down, so that the neighbors can consider it for interarea routes.
To configure areas, you can perform the following tasks:
| Copyright © 2008, Juniper Networks, Inc. All rights reserved. Trademark Notice. | |