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5.19 BGP实验

news 来源：原创 2025/5/16 9:35:45

实验拓扑

实验要求：

1、在R4上配置preval策略，确保R4通过R2到达5.5.5.5/32

2、在R4上配置AS Path策略，确保R4通过R3到达9.9.9.9/32

3、在R2和R3上配置MED策略，确保R4通过R3到达6.6.6.6/32

4、在R2上配置Local Preference策略，确保R1通过R2到达4.4.4.4/32

5、在R1上配置Local Preference策略，确保R1通过R2到达8.8.8.8/32

6、配置负载均衡，确保R4通过R2和R3到达55.55.55.55/32

7、在R5上配置As策略，AS 5不接受任何始发于AS 123的路由

8、在R4上配置自定义Community策略，确保7.7.7.7/24路由不会被发布到AS 5

9、IBGP使用环回接口建邻，EBGP使用物理接口建邻

10、BGP宣告路由时，仅宣告24网段的用户路由

三、具体配置

配置IP和环回地址

interface GigabitEthernet0/0/0
ip address 15.0.0.1 255.255.255.0

interface GigabitEthernet0/0/1
ip address 12.0.0.1 255.255.255.0

interface GigabitEthernet0/0/2
ip address 13.0.0.1 255.255.255.0

interface LoopBack0
ip address 1.1.1.1 255.255.255.255

interface LoopBack1
ip address 192.168.100.1 255.255.255.0
ospf network-type broadcast

interface GigabitEthernet0/0/0
ip address 12.0.0.2 255.255.255.0

interface GigabitEthernet0/0/1
ip address 24.0.0.2 255.255.255.0

interface LoopBack0

ip address 2.2.2.2 255.255.255.255

interface LoopBack1
ip address 192.168.20.1 255.255.255.0
ospf network-type broadcast

interface GigabitEthernet0/0/0
ip address 13.0.0.3 255.255.255.0

interface GigabitEthernet0/0/1
ip address 34.0.0.3 255.255.255.0

interface LoopBack0
ip address 3.3.3.3 255.255.255.255

interface LoopBack1
ip address 192.168.30.1 255.255.255.0
ospf network-type broadcast

interface GigabitEthernet0/0/0
ip address 24.0.0.4 255.255.255.0

interface GigabitEthernet0/0/1
ip address 34.0.0.4 255.255.255.0

interface LoopBack1
ip address 192.168.1.1 255.255.255.0

interface LoopBack2
ip address 192.168.2.1 255.255.255.0

interface LoopBack3
ip address 192.168.3.1 255.255.255.0

interface GigabitEthernet0/0/0
ip address 15.0.0.5 255.255.255.0

interface LoopBack0
ip address 192.168.10.1 255.255.255.0

interface LoopBack1
ip address 192.168.11.1 255.255.255.0

interface LoopBack2
ip address 192.168.12.1 255.255.255.0

配置结果：

<r1>display ip interface brief

Interface IP Address/Mask Physical Protocol
GigabitEthernet0/0/0 15.0.0.1/24 up up
GigabitEthernet0/0/1 12.0.0.1/24 up up
GigabitEthernet0/0/2 13.0.0.1/24 up up
LoopBack0 1.1.1.1/32 up up(s)
LoopBack1 192.168.100.1/24 up up(s)

<R2>display IP interface brief

Interface IP Address/Mask Physical Protocol
GigabitEthernet0/0/0 12.0.0.2/24 up up
GigabitEthernet0/0/1 24.0.0.2/24 up up
GigabitEthernet0/0/2 unassigned   down down
LoopBack0 2.2.2.2/32 up up(s)
LoopBack1 192.168.20.1/24 up up(s)

<R3>display ip interface brief

Interface IP Address/Mask Physical Protocol
GigabitEthernet0/0/0 13.0.0.3/24 up up
GigabitEthernet0/0/1 34.0.0.3/24 up up
GigabitEthernet0/0/2 unassigned down down
LoopBack0 3.3.3.3/32 up up(s)
LoopBack1 192.168.30.1/24 up up(s)

<R4>display ip interface brief

Interface IP Address/Mask Physical Protocol
GigabitEthernet0/0/0 24.0.0.4/24 up up
GigabitEthernet0/0/1 34.0.0.4/24 up up
GigabitEthernet0/0/2 unassigned down down
LoopBack1 192.168.1.1/24 up up(s)
LoopBack2 192.168.2.1/24 up up(s)
LoopBack3 192.168.3.1/24 up up(s)

<R5>display ip interface brief

Interface IP Address/Mask Physical Protocol
GigabitEthernet0/0/0 15.0.0.5/24 up up
GigabitEthernet0/0/1 unassigned   down down
GigabitEthernet0/0/2 unassigned down down
LoopBack0 192.168.10.1/24 up up(s)
LoopBack1 192.168.11.1/24 up up(s)
LoopBack2 192.168.12.1/24 up up(s)

AS 123内部IGP搭建

OSPF配置

[r1-ospf-1]display this

ospf 1 router-id 1.1.1.1
area 0.0.0.0
network 1.1.1.1 0.0.0.0
network 12.0.0.1 0.0.0.0
network 13.0.0.1 0.0.0.0
network 15.0.0.1 0.0.0.0
network 192.168.100.0 0.0.0.255

[R2-ospf-1]display this

ospf 1 router-id 2.2.2.2
area 0.0.0.0
network 2.2.2.2 0.0.0.0

network 12.0.0.2 0.0.0.0
network 24.0.0.2 0.0.0.0
network 192.168.20.0 0.0.0.255

[R3-ospf-1]display this

ospf 1 router-id 3.3.3.3
area 0.0.0.0
network 3.3.3.3 0.0.0.0
network 13.0.0.3 0.0.0.0

network 34.0.0.3 0.0.0.0
network 192.168.30.0 0.0.0.255

配置结果检查

<r1>display ospf routing

OSPF Process 1 with Router ID 1.1.1.1
Routing Tables

Routing for Network
Destination Cost Type NextHop AdvRouter Area
1.1.1.1/32 0 Stub 1.1.1.1 1.1.1.1 0.0.0.0
12.0.0.0/24 1 Transit 12.0.0.1 1.1.1.1 0.0.0.0
13.0.0.0/24 1 Transit 13.0.0.1 1.1.1.1 0.0.0.0
15.0.0.0/24 1 Stub 15.0.0.1 1.1.1.1 0.0.0.0
192.168.100.0/24 0 Stub 192.168.100.1 1.1.1.1 0.0.0.0
2.2.2.2/32 1 Stub 12.0.0.2 2.2.2.2 0.0.0.0
3.3.3.3/32 1 Stub 13.0.0.3 3.3.3.3 0.0.0.0
24.0.0.0/24 2 Stub 12.0.0.2 2.2.2.2 0.0.0.0
34.0.0.0/24 2 Stub 13.0.0.3 3.3.3.3 0.0.0.0
192.168.20.0/24 1 Stub 12.0.0.2 2.2.2.2 0.0.0.0
192.168.30.0/24 1 Stub 13.0.0.3 3.3.3.3 0.0.0.0

Total Nets: 11
Intra Area: 11 Inter Area: 0 ASE: 0 NSSA: 0

BGP建立邻居环节

BGP建邻配置及注意事项

R1与R2、R3是IBGP对等体关系，要求使用环回地址建立邻居关系，需要修改数据包的元IP地址为环回地址（对等体关系双方均需要修改）

bgp 123
router-id 1.1.1.1
peer 2.2.2.2 as-number 123
peer 2.2.2.2 connect-interface LoopBack0
peer 3.3.3.3 as-number 123
peer 3.3.3.3 connect-interface LoopBack0
peer 15.0.0.5 as-number 500

bgp 123

router-id 2.2.2.2

peer 1.1.1.1 as-number 123

peer 1.1.1.1 connect-interface LoopBack0

peer 24.0.0.4 as-number 400

bgp 123

router-id 3.3.3.3

peer 1.1.1.1 as-number 123

peer 1.1.1.1 connect-interface LoopBack0

peer 34.0.0.4 as-number 400

bgp 400

router-id 4.4.4.4

peer 24.0.0.2 as-number 123

peer 34.0.0.3 as-number 123

bgp 500

router-id 5.5.5.5

peer 15.0.0.1 as-number 123

建邻结果检查

<r1>display bgp peer

BGP local router ID : 1.1.1.1
Local AS number : 123
Total number of peers : 3 Peers in established state : 3

Peer V AS MsgRcvd MsgSent OutQ Up/Down State Pre
fRcv

2.2.2.2 4 123 20 19 0 00:15:59 Established
4
3.3.3.3 4 123 20 19 0 00:15:59 Established
4
15.0.0.5 4 500 21 22 0 00:16:28 Established

BGP宣告

进入BGP进程：

[r1]bgp 123

宣告网段：

[r1-bgp]network 192.168.100.0 24

network 192.168.100.0 24

network 192.168.20.0 24

network 192.168.30.0 24

network 192.168.1.0

network 192.168.2.0

network 192.168.3.0

network 192.168.10.0

network 192.168.11.0

network 192.168.12.0

BGP宣告结果检查

<R2>display bgp routing-table

Total Number of Routes: 8
Network NextHop MED LocPrf PrefVal Path/Ogn

*> 192.168.1.0 24.0.0.4 0 0 400i
*> 192.168.2.0 24.0.0.4 0 0 400i
*> 192.168.3.0 24.0.0.4 0 0 400i
*>i 192.168.10.0 15.0.0.5 0 100 0 500i
*>i 192.168.11.0 15.0.0.5 0 100 0 500i
*>i 192.168.12.0 15.0.0.5 0 100 0 500i
*> 192.168.20.0 0.0.0.0 0 0 i
*>i 192.168.100.0 1.1.1.1 0 100 0 i

<R3>display bgp routing-table

Total Number of Routes: 8
Network NextHop MED LocPrf PrefVal Path/Ogn

*> 192.168.1.0 34.0.0.4 0 0 400i
*> 192.168.2.0 34.0.0.4 0 0 400i
*> 192.168.3.0 34.0.0.4 0 0 400i
*>i 192.168.10.0 15.0.0.5 0 100 0 500i
*>i 192.168.11.0 15.0.0.5 0 100 0 500i
*>i 192.168.12.0 15.0.0.5 0 100 0 500i
*> 192.168.30.0 0.0.0.0 0 0 i
*>i 192.168.100.0 1.1.1.1 0 100 0 i

PreVal策略：

ip ip-prefix Preval permit 192.168.10.0 24 greater-equal 24 less-equal 24

route-policy Preval permit node 10
if-match ip-prefix Preval
apply preferred-value 100
route-policy Preval permit node 20

bgp 400
peer 24.0.0.2 route-policy Preval import

修改结果：

[R4]display bg routing-table

Total Number of Routes: 13
Network NextHop MED LocPrf PrefVal Path/Ogn

*> 192.168.10.0 24.0.0.2 100 123 500i
* 34.0.0.3 0 123 500i

AS_Path策略：

ip ip-prefix AS_Path permit 192.168.11.0 24 greater-equal 24 less-equal 24

route-policy AS_Path permit node 10
if-match ip-prefix AS_Path
apply as-path none overwrite
Y
route-policy AS_Path permit node 20
bgp 123
peer 34.0.0.4 route-policy AS_Path export

查看修改结果：

<R4>display bgp routing-table 192.168.11.0 24

From: 34.0.0.3 (3.3.3.3)

AS-path 123

From: 24.0.0.2 (2.2.2.2)

AS-path 123 500

MED策略：

ip ip-prefix MED permit 192.168.12.0 24 greater-equal 24 less-equal 24
route-policy MED permit node 10
if-match ip-prefix MED
apply cost 500
route-policy MED permit node 20
bgp 400
peer 24.0.0.2 route-policy MED import

Local Preference策略

ip ip-prefix LP permit 192.168.1.0 24 greater-equal 24 less-equal 24

route-policy LP permit node 10
if-match ip-prefix LP
apply local-preference 200
route-policy LP permit node 20
bgp 123
peer 2.2.2.2 route-policy LP import

ip ip-prefix LP2 permit 192.168.2.0 24 greater-equal 24 less-equal 24

route-policy LP2 permit node 10
if-match ip-prefix LP2
apply local-preference 200
route-policy LP2 permit node 20
bgp 123
peer 3.3.3.3 route-policy LP2 import

负载均衡：

[r1-bgp]maximum load-balancing ibgp 2

AS路径过滤器：

ip as-path-filter 1 deny ^$

ip as-path-filter 1 permit .*

bgp 123

peer 15.0.0.5 as-path-filter 1 export

COMMUNITY策略

ip ip-prefix com permit 192.168.3.0 24 greater-equal 24 less-equal 24

route-policy com permit node 10
if-match ip-prefix com
apply community no-export
route-policy com permit node 20

bgp 123
peer 24.0.0.2 advertise-community
peer 34.0.0.3 advertise-community
peer 24.0.0.2 route-policy com export
peer 34.0.0.3 route-policy com export

R2/R3