Avaya Configuring IP Exterior Gateway Protocols (BGP and EGP) Manuel d'utilisateur télécharger pdf (Page 58)

Configuring IP Exterior Gateway Protocols (BGP and EGP)

4-14

308628-14.00 Rev 00

Defining a Static Black Hole for a Supernet

A router that advertises an aggregate route by using a supernet address to

represent multiple explicit routes must be able to discard packets that match the

supernet address but that do not match any of the explicit routes.

For example, consider a router that advertises an aggregate route using the

supernet address 192.32.0.0/255.255.248. The supernet address represents eight

specific networks: 192.32.0.0 to 192.32.7.0. After the aggregate route has been

propagated, the router receives network traffic for each of these specific

destinations.

At some point, the router loses connectivity to network 192.32.3.0, one of the

networks in the supernet. The router continues to forward traffic that matches

destinations 0.0 to 2.0 and 4.0 to 7.0. However, the router can no longer find a

complete match in the routing table for the disconnected network, 3.0. The router

must drop all traffic destined for 192.32.3.0.

To force the router to drop the packet for an unmatched destination, you configure

a special type of static route for a supernet called a black hole. To do so:

• Enter the supernet address/mask pair as the destination IP address and address

mask.

• To create the black hole, enter the black hole encoding (255.255.255.255) as

the next-hop address and the next-hop mask.

1 2 ... 53 54 55 56 57 58 59 60 61 62 63 ... 307 308

Pas de commentaire

Avaya Configuring IP Exterior Gateway Protocols (BGP and EGP) Manuel d'utilisateur Page 58