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Conﬁguring gated

Conﬁguring the OSPF Protocol

Chapter 3 81

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 theexception of conﬁgured stub areas). Asingle 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

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HP 11i Manual do Utilizador Página 81