HP 11i Manual do Utilizador descarregar pdf (Página 80)

Conﬁguring gated

Conﬁguring the OSPF Protocol

Chapter 380

In Figure 3-12, there are two possible packet routes between nodesA and

D: one route goes through node B and the other route goes through node

C. The cost of each route is calculated as follows:

Node A to node B and node B to node D: 5+5 = 10

Node A to node C and node C to node D: 5+10 = 15

The lowest cost OSPF path between nodes A and D is therefore through

node B. However, packets are rerouted through node C if there is a link

failure between node B and LAN 2.

You can optionally deﬁne cost in the following places in the

/etc/gated.conf ﬁle:

• In a defaults statement in the OSPF protocol conﬁguration, which

applies only to AS boundary routers. This cost deﬁnition applies to

routes to destinations outside the AS. These routes may have been

derived from other routing protocols, such as EGP. See “AS External

Routes (AS Boundary Routers Only)” on page 80 for more

information.

• In the export statement in the Control class in the

/etc/gated.conf ﬁle, which applies only to AS boundary routers.

This cost deﬁnition applies to routes that are exported from the AS

boundary router to routers in other autonomous systems.

• In the stub area deﬁnition of the OSPF protocol conﬁguration. This

cost deﬁnition speciﬁes the cost of the default summary link that is

advertised in the area.

• In the stubhosts deﬁnition of the OSPF protocol conﬁguration. This

cost deﬁnition speciﬁes the cost of a point-to-point interface between

the router and a non-OSPF host.

• In the subhosts deﬁnition of the OSPF protocol conﬁguration. This

cost deﬁnition speciﬁes the cost of a point-to-point interface between

the backbone router and a non-OSPF host.

AS External Routes (AS Boundary Routers Only)

AS external (ASE) routes are paths to destinations that are outside the

AS. Most ASE routes are routes to speciﬁc destinations. AS boundary

routers specify the ASE routes through another routing protocol, such as

EGP, or through conﬁgured routes.

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HP 11i Manual do Utilizador Página 80