R1的配置：
R1#SHOW RUN
Building configuration...
Building configuration...
Current configuration : 1529 bytes
!
version 12.3
!
version 12.3
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R1
!
boot-start-marker
boot-end-marker
!
!
no aaa new-model
!
resource policy
!
ip subnet-zero
!
!
ip cef
no ip dhcp use vrf connected
interface Serial1/0
ip address 12.0.0.1 255.0.0.0
serial restart-delay 0
no dce-terminal-timing-enable
!
interface Serial1/1
ip address 14.0.0.1 255.0.0.0
serial restart-delay 0
no dce-terminal-timing-enable
!
router bgp 1
no synchronization
bgp log-neighbor-changes
neighbor 12.0.0.2 remote-as 2
neighbor 12.0.0.2 weight 7000
neighbor 14.0.0.4 remote-as 4
neighbor 14.0.0.4 weight 6000
no auto-summary
!
R2的配置：
R2#SHOW RUN
Building configuration...
Building configuration...
Current configuration : 1467 bytes
!
version 12.3
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R2
!
boot-start-marker
boot-end-marker
!
!
no aaa new-model
!
resource policy
!
ip subnet-zero
!
!
ip cef
no ip dhcp use vrf connected
!
version 12.3
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R2
!
boot-start-marker
boot-end-marker
!
!
no aaa new-model
!
resource policy
!
ip subnet-zero
!
!
ip cef
no ip dhcp use vrf connected
interface Serial1/0
ip address 12.0.0.2 255.0.0.0
serial restart-delay 0
no dce-terminal-timing-enable
!
interface Serial1/1
ip address 23.0.0.2 255.0.0.0
serial restart-delay 0
no dce-terminal-timing-enable
!
router bgp 2
no synchronization
bgp log-neighbor-changes
neighbor 12.0.0.1 remote-as 1
neighbor 23.0.0.3 remote-as 3
no auto-summary
!
ip address 12.0.0.2 255.0.0.0
serial restart-delay 0
no dce-terminal-timing-enable
!
interface Serial1/1
ip address 23.0.0.2 255.0.0.0
serial restart-delay 0
no dce-terminal-timing-enable
!
router bgp 2
no synchronization
bgp log-neighbor-changes
neighbor 12.0.0.1 remote-as 1
neighbor 23.0.0.3 remote-as 3
no auto-summary
!
R3的配置：
R3>EN
R3#SHOW RUN
Building configuration...
R3#SHOW RUN
Building configuration...
Current configuration : 1536 bytes
!
version 12.3
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R3
!
!
version 12.3
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R3
!
interface Loopback3
ip address 3.0.0.3 255.0.0.0
!
interface Serial1/0
ip address 23.0.0.3 255.0.0.0
serial restart-delay 0
no dce-terminal-timing-enable
!
interface Serial1/1
ip address 34.0.0.3 255.0.0.0
serial restart-delay 0
no dce-terminal-timing-enable
!
ip address 3.0.0.3 255.0.0.0
!
interface Serial1/0
ip address 23.0.0.3 255.0.0.0
serial restart-delay 0
no dce-terminal-timing-enable
!
interface Serial1/1
ip address 34.0.0.3 255.0.0.0
serial restart-delay 0
no dce-terminal-timing-enable
!
router bgp 3
no synchronization
bgp log-neighbor-changes
network 3.0.0.0
neighbor 23.0.0.2 remote-as 2
neighbor 34.0.0.4 remote-as 4
no auto-summary
no synchronization
bgp log-neighbor-changes
network 3.0.0.0
neighbor 23.0.0.2 remote-as 2
neighbor 34.0.0.4 remote-as 4
no auto-summary
！
R4的配置：
R4#SHOW RUN
Building configuration...
Building configuration...
Current configuration : 1467 bytes
!
version 12.3
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R4
!
!
version 12.3
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R4
!
interface Serial1/0
ip address 34.0.0.4 255.0.0.0
serial restart-delay 0
no dce-terminal-timing-enable
!
interface Serial1/1
ip address 14.0.0.4 255.0.0.0
serial restart-delay 0
no dce-terminal-timing-enable
!
ip address 34.0.0.4 255.0.0.0
serial restart-delay 0
no dce-terminal-timing-enable
!
interface Serial1/1
ip address 14.0.0.4 255.0.0.0
serial restart-delay 0
no dce-terminal-timing-enable
!
router bgp 4
no synchronization
bgp log-neighbor-changes
neighbor 14.0.0.1 remote-as 1
neighbor 34.0.0.3 remote-as 3
no auto-summary
!
no synchronization
bgp log-neighbor-changes
neighbor 14.0.0.1 remote-as 1
neighbor 34.0.0.3 remote-as 3
no auto-summary
!
R1的变化过程：
R1#show ip bgp
BGP table version is 2, local router ID is 14.0.0.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
BGP table version is 2, local router ID is 14.0.0.1
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
* 3.0.0.0 12.0.0.2 0 2 3 i
*> 14.0.0.4 0 4 3 i
* 3.0.0.0 12.0.0.2 0 2 3 i
*> 14.0.0.4 0 4 3 i
R1#
R1#conf t
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#router bgp 1
R1(config-router)#nei
R1(config-router)#neighbor 14.0.0.4 w
R1(config-router)#neighbor 14.0.0.4 weight 6000
R1(config-router)#end
R1#
R1#conf t
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#router bgp 1
R1(config-router)#nei
R1(config-router)#neighbor 14.0.0.4 w
R1(config-router)#neighbor 14.0.0.4 weight 6000
R1(config-router)#end
R1#
R1#clear ip bgp 14.0.0.4 soft in
R1#show ip bgp
BGP table version is 3, local router ID is 14.0.0.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
BGP table version is 3, local router ID is 14.0.0.1
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
* 3.0.0.0 12.0.0.2 0 2 3 i
*> 14.0.0.4 6000 4 3 i
* 3.0.0.0 12.0.0.2 0 2 3 i
*> 14.0.0.4 6000 4 3 i
R1#conf t
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#router bgp 1
R1(config-router)#nei
R1(config-router)#neighbor 12.0.0.2 wei
R1(config-router)#neighbor 12.0.0.2 weight 7000
R1#
R1#clear ip bgp 12.0.0.2 soft in
R1#show ip bgp
BGP table version is 4, local router ID is 14.0.0.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
BGP table version is 4, local router ID is 14.0.0.1
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
*> 3.0.0.0 12.0.0.2 7000 2 3 i
* 14.0.0.4 6000 4 3 i
*> 3.0.0.0 12.0.0.2 7000 2 3 i
* 14.0.0.4 6000 4 3 i
