Dell BigIron RX Series, Configuration Manual

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BigIron RX Series Configuration Guide 755
53-1002253-01
BGP Null0 routing
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BGP Null0 routing
BGP can use the null0 route to resolve its next hop. Thus, null0 route in the routing table (for
example, static route) is considered as a valid route by BGP. If the next hop for BGP resolves into a
null0 route, the BGP route is also installed as a null0 route in the routing table.
The null0 routing feature allows network administrators to block certain network prefixes, by using
null0 routes and route-maps. The combined use of null0 routes and route maps blocks traffic from
a particular network prefix, telling a remote router to drop all traffic for this network prefix by
redistributing a null0 route into BGP.
Figure 113 shows a topology for a null0 routing application example.
FIGURE 113 Sample Null0 routing application
The following steps configure a null0 routing application for stopping denial of service attacks from
remote hosts on the internet.
Configuration steps
1. Select one router, Router 6, to distribute null0 routes throughout the BGP network.
2. Configure a route-map to match a particular tag (50) and set the next-hop address to an
unused network address (199.199.1.1).
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.
R1
AS 100
R2
R3
R6 R7 R5
R4
Internet