Information Technology Reference
In-Depth Information
The BGP RIB on R4 is unaffected, because R8 prefers the path via R4,
so R4 still has only one entry, as shown in Table 7-24.
Step 5
Table 7-24
BGP Paths on R4
Path
BGP Next Hop
AS_PATH
MED
IGP Metric
1
*
R6
300 400
6
10
For Step 6 and beyond, there is no best-path change. The network is
converged. The best path for each router is shown in Figure 7-26. The
arrows indicate the packet-forwarding direction. For example, the best
path for R1 is consistently via R2.
Step 6
Figure 7-26
Packet Forwarding Directions with the Best Paths
AS 100
RR
RR
50
R8
R1
15
Client
20
6
Client
R2
Client
R3
R4
MED: 10
MED: 5
MED: 6
AS 200
AS 300
R5
R6
172.16.0.0/16
AS 400
172.16.0.0/16
R7
Enabling the
deterministic-MED
Option
The best path in this section is modified
using a few steps from the previous scenario. The following steps describe the process:
Each of the three border routers in AS 100 receives the prefix from
external neighbors and announces the prefix internally with the next hop
set to itself, respectively.
Step 1