Avaya Configuring IP, ARP, RARP, RIP, and OSPF Services Instrukcja Użytkownika Pobierz pdf (Strona 44)

Configuring IP, ARP, RARP, RIP, and OSPF Services

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Route Weights

Route weight calculation is an internal tool that IP uses to facilitate the selection

of the best route among alternative routes to the same destination. Route-selection

criteria are encoded into the route weight in a way that allows IP to compare

routes simply by comparing their weight values, regardless of route sources.

Appendix C contains a worksheet that you can use to calculate route weights in

your configuration.

Route weight calculation increases the efficiency of the route selection process. It

also reduces the size of the routing database because all route selection parameters

for each route are encoded in a single integer — the weight value — rather than

stored in separate variables.

Using selection criteria encoded in the route weight, IP chooses routes in the

following order:

1. The route with the highest preference value (see “Route Preferences” on page

1-21)

2. A direct route with the lowest metric

3. An OSPF intra-area route with the lowest metric

4. An OSPF interarea route with the lowest metric

5. An OSPF type 1 external route with the lowest metric

6. An OSPF type 2 external route with ASE metric support enabled

7. A BGP route with the highest LOCAL_PREF value

8. A RIP route with the lowest metric

9. An EGP route with the lowest metric

10. A static route with the lowest metric

Note:

If OSPF is configured to propagate external routes using the route

weight as the type 2 metric, routes that are received as OSPF ASE type 2

routes are evaluated according to their respective origins (for example, RIP or

BGP).

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Avaya Configuring IP, ARP, RARP, RIP, and OSPF Services Instrukcja Użytkownika Strona 44