Step 8 - Lowes IGP metric to BGP next-hop ( 13 step selection route BGP)

8- Prefer with Lowes IGP metric to BGP next-hop

                         + Giá trị metric đến nexthop càng nhỏ sẽ tốt hơn

R1#show run | se router router bgp 1  no synchronization  network 8.8.8.0 mask 255.255.255.0  neighbor 10.1.12.2 remote-as 234  neighbor 10.1.13.3 remote-as 234  no auto-summary

R2#show run | se router router bgp 234  no synchronization  neighbor 10.1.12.1 remote-as 1  neighbor 10.1.24.4 remote-as 234  no auto-summary

R3#show run | se router router bgp 234  neighbor 10.1.13.1 remote-as 1  neighbor 10.1.34.4 remote-as 234  no auto-summary

R4#show run | se router router bgp 234  neighbor 10.1.24.2 remote-as 234  neighbor 10.1.34.3 remote-as 234  no auto-summary ! Interface fastethernet 0/0  ip ospf cost 20

R4#show ip route ospf

     10.0.0.0/24 is subnetted, 4 subnets

O       10.1.13.0 [110/20] via 10.1.34.3, 00:05:44, FastEthernet0/1

O       10.1.12.0 [110/30] via 10.1.24.2, 00:02:56, FastEthernet0/0

R4#show ip bgp        

BGP table version is 3, local router ID is 4.4.4.4

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

              r RIB-failure, S Stale

Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path

*>i8.8.8.0/24       10.1.13.1                0    100      0 1 i

* i                            10.1.12.1                0    100      0 1 i

Xét từng bước sau:

1. Weight: bằng nhau 0
2. Local prefer: bằng nhau 100
3. Perfer the path was locally..: bằng nhau
4. AS-path: bằng nhau
5. Origin type : bằng nhau

6. Med: bằng nhau

7. Prefer eBGP over iBGP: cùng iBGP
8. Prefer with lowes IGP metric to BGP next-hop : BREAK
9. Nhận xét: R4 học mang 8.8.8.0/24 qua R3 có next-hop là 10.1.13.1. Vì cost IGP tới 10.1.13.0 = 20 < 10.1.12.0 = 30