
Configuring IP, ARP, RARP, RIP, and OSPF Services
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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, as follows:
• 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.
Customizing Router Discovery
Before a host can send IP datagrams beyond its directly attached subnet, the host
must discover the address of at least one operational router on that subnet. Router
Discovery is an extension of the Internet Control Message Protocol (ICMP) that
enables hosts attached to multicast or broadcast networks to discover the IP
addresses of their neighboring routers.
Routers configured with Router Discovery periodically multicast or broadcast a
router advertisement from each of their interfaces, announcing the IP address or
addresses of that interface. Hosts discover the addresses of their neighboring
routers by listening for these advertisements. Hosts will use the router with the
highest preference level as a gateway.
You can use the BCC or Site Manager to choose the operating characteristics of
Router Discovery on the interface, as described under the following topics:
Topic Page
Enabling and Disabling Router Discovery
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Choosing a Broadcast Type 3-64
Specifying the Time Interval Between Advertisements 3-65
Configuring the Lifetime of Advertised Addresses 3-66
Specifying Interface Preference 3-67
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