Configuring gated
Configuring the OSPF Protocol
gated supports the use of route information from other autonomous systems that use other routing protocols, such as EGP. AS boundary routers send AS external link advertisements and flood the AS with advertisements (with the exception of configured stub areas). A single AS external link advertisement is sent for each external route that the AS boundary router has learned about.
Externally defined routing information and OSPF routing information are maintained separately. In addition, you can tag the externally defined routing information, to identify and store the source of the information along with the route information.
Statements in the Control class of the /etc/gated.conf file control the importing of routes from routing protocols to a gated forwarding table and the exporting of routes from the gated forwarding table. See “Importing and Exporting Routes” on page 97 for more information.
You must specify the defaults statements in the OSPF protocol configuration only for AS boundary routers. These statements specify how external routing information is handled by the OSPF protocol. You can define the following in the defaults statements:
•preference specifies the preference value given to the ASE routes imported from other autonomous systems. The preference value determines the order of routes to the same destination in the routing table. gated allows one route to a destination per protocol for each AS. In case of multiple routes, the route used is determined by the lowest preference value (see “Specifying Route Preference” on page 94 for more information). If a preference value is not specified, ASE routes are imported with a preference of 150.
Default: 150
Range: 0 (most preferred) – 255 (least preferred)
•cost specifies the cost associated with an OSPF route that is exported to other AS boundary routers.
Default: 0
Range: 0 – 65535
•tag specifies an OSPF tag placed on all routes exported by gated into OSPF. You can tag each external route by the AS boundary router to identify the source of the routing information. The tag
Chapter 3 | 81 |
