R4.67 # show bgp route all Routes:
| Destination | Peer | Next-Hop | LPref | Weight | MED | AS-Path |
|---|---|---|---|---|---|---|
| ---------------------------------------------------------------------------- | ||||||
| *>i 192.51.100.0/28 | 10.0.0.1 | 10.0.0.1 | 100 | 1 | 0 | 64500 |
| *>i 192.51.100.16/28 | 10.0.0.1 | 10.0.0.1 | 100 | 1 | 0 | 64500 |
| *>i 192.51.100.32/28 | 10.0.0.1 | 10.0.0.1 | 100 | 1 | 0 | 64500 |
| *>i 192.51.100.48/28 | 10.0.0.1 | 10.0.0.1 | 100 | 1 | 0 | 64500 |
| *>i 192.51.100.64/28 | 10.0.0.1 | 10.0.0.1 | 100 | 1 | 0 | 64500 |
| *>i 203.0.113.1/32 | 10.0.0.1 | 192.168.2.66 | 100 | 1 | 0 | 64500 |
Flags: (*) Preferred BGP route, (>) Active, (d) Suppressed, (h) History (s) Stale, (m) Multipath, (u) Unfeasible Origin: (?) Incomplete, (e) EGP, (i) IGP BGP Route Statistics Total Rxed Routes : 6 Feasible Routes : 6 Active Routes : 6 Rejected Routes : 0 Unfeasible Routes : 0 Route Statistics on Session Type Routes from Int Peer: 0 Routes from Ext Peer: 6 Switch.68 # rtlookup 203.0.113.1 Ori Destination Gateway Mtr Flags VLAN Duration #be 203.0.113.1/32 192.168.2.66 1 UG-D---um--f BH_VLAN 0d:1h:5m:5s
Note
For the above solution, the edge routers, R1 through R4, may still export the route to the target network to external AS(s), but the traffic is dropped at the edge of the provider network.An alternative solution for protecting the network is to perform step 1 only on a designated sink router, (R5 in Black Hole Routing Using BGP) and redistributes the black hole next-hop using iBGP to R2 through R4. When traffic arrives at routers R2 through R4, it is forwarded to R5, since R2–R4 have iBGP routes that resolve the black hole next-hop to R5. Router R5 then discards the traffic.
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