Brocade FastIron Ethernet Switch Layer 3 Routing Configuration Guide - Manual (Page 431)

BGP4 null0 routing
BGP4 considers the null0 route in the routing table (for example, static route) as a valid route, and can
use the null0 route to resolve the next hop. If the next hop for BGP4 resolves into a null0 route, the
BGP4 route is also installed as a null0 route in the routing table.
The null0 routing feature allows network administrators to block certain network prefixes using null0
routes and route-maps, directing a remote device to drop all traffic for a network prefix by redistributing
a null0 route into BGP4.
This example shows a topology for a null0 routing application example.
FIGURE 34 SAMPLE null0 routing application
Configuring BGP4 null0 routing
The following example configures a null0 routing application to stop denial of service attacks from
remote hosts on the Internet.
1. Select a device, for example, device 6, to distribute null0 routes throughout the BGP4 network.
2. To configure a route-map perform the following step.
• Configure a route-map to match a particular tag (50) and set the next-hop address to an unused
network address (10.199.1.1).
3. Set the local-preference to a value higher than any possible internal or external local-preference (50).
4. Complete the route map by setting origin to IGP.
5. On device 6, redistribute the static routes into BGP4, using route-map route-map-name (redistribute
static route-map block user).
BGP4 null0 routing
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