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介绍OSPF-BGP联动功能的配置过程,使得当路由器重启后,网络流量不发生中断。
组网需求
如图1所示,所有路由器均为BGP设备,RouterD和RouterE之间建立EBGP连接。在AS10内的部分路由器之间建立IBGP连接,并且使用OSPF作为IGP协议。
要求在RouterB上使能OSPF-BGP联动功能,使得当RouterB重启后,从RouterA到AS20的流量不发生中断。
配置思路
采用如下的思路配置OSPF-BGP联动功能。
在RouterA、RouterB、RouterC和RouterD(除去10.2.1.1/30)上使能OSPF协议,指定相同区域内的网段。
在RouterA、RouterB、RouterC和RouterD(除去10.2.1.1/30)之间建立IBGP连接。
在RouterC上配置OSPF协议的开销值。
在RouterD和RouterE之间配置EBGP连接。
在RouterD上配置BGP引入直连路由和OSPF路由。
在RouterE上配置BGP。
数据准备
为完成此配置例,需准备如下的数据:
RouterA的Router ID 1.1.1.1,所在的AS号10,运行的OSPF进程号1,在区域0的网段是10.1.1.0/30,10.1.2.0/30。
RouterB的Router ID 2.2.2.2,所在的AS号10,运行的OSPF进程号1,在区域0的网段是10.1.1.0/30,10.1.3.0/30。
RouterC的Router ID 3.3.3.3,所在的AS号10,运行的OSPF进程号1,在区域0的网段是10.1.2.0/30,10.1.4.0/30。
RouterD的Router ID 4.4.4.4,所在的AS号10,运行的OSPF进程号1,在区域0的网段是10.1.3.0/30,10.1.4.0/30。
RouterE的Router ID 5.5.5.5,所在的AS号20。
操作步骤
- 配置各接口的IP地址(略)
- 配置OSPF的基本功能(略)
- 配置IBGP全连接
# 配置RouterA。
<RouterA> system-view
[RouterA] interface loopback 0
[RouterA-LoopBack0] ip address 1.1.1.1 32
[RouterA-LoopBack0] quit
[RouterA] bgp 10
[RouterA-bgp] router-id 1.1.1.1
[RouterA-bgp] peer 2.2.2.2 as-number 10
[RouterA-bgp] peer 2.2.2.2 connect-interface LoopBack 0
[RouterA-bgp] peer 3.3.3.3 as-number 10
[RouterA-bgp] peer 3.3.3.3 connect-interface LoopBack 0
[RouterA-bgp] peer 4.4.4.4 as-number 10
[RouterA-bgp] peer 4.4.4.4 connect-interface LoopBack 0
[RouterA-bgp] quit
# 配置RouterB。
<RouterB> system-view
[RouterB] interface loopback 0
[RouterB-LoopBack0] ip address 2.2.2.2 32
[RouterB-LoopBack0] quit
[RouterB] bgp 10
[RouterB-bgp] router-id 2.2.2.2
[RouterB-bgp] peer 1.1.1.1 as-number 10
[RouterB-bgp] peer 1.1.1.1 connect-interface LoopBack 0
[RouterB-bgp] peer 3.3.3.3 as-number 10
[RouterB-bgp] peer 3.3.3.3 connect-interface LoopBack 0
[RouterB-bgp] peer 4.4.4.4 as-number 10
[RouterB-bgp] peer 4.4.4.4 connect-interface LoopBack 0
[RouterB-bgp] quit
# 配置RouterC。
<RouterC> system-view
[RouterC] interface loopback 0
[RouterC-LoopBack0] ip address 3.3.3.3 32
[RouterC-LoopBack0] quit
[RouterC] bgp 10
[RouterC-bgp] router-id 3.3.3.3
[RouterC-bgp] peer 1.1.1.1 as-number 10
[RouterC-bgp] peer 1.1.1.1 connect-interface LoopBack 0
[RouterC-bgp] peer 2.2.2.2 as-number 10
[RouterC-bgp] peer 2.2.2.2 connect-interface LoopBack 0
[RouterC-bgp] peer 4.4.4.4 as-number 10
[RouterC-bgp] peer 4.4.4.4 connect-interface LoopBack 0
[RouterC-bgp] quit
# 配置RouterD。
<RouterD> system-view
[RouterD] interface loopback 0
[RouterD-LoopBack0] ip address 4.4.4.4 32
[RouterD-LoopBack0] quit
[RouterD] bgp 10
[RouterD-bgp] router-id 4.4.4.4
[RouterD-bgp] peer 1.1.1.1 as-number 10
[RouterD-bgp] peer 1.1.1.1 connect-interface LoopBack 0
[RouterD-bgp] peer 2.2.2.2 as-number 10
[RouterD-bgp] peer 2.2.2.2 connect-interface LoopBack 0
[RouterD-bgp] peer 3.3.3.3 as-number 10
[RouterD-bgp] peer 3.3.3.3 connect-interface LoopBack 0
[RouterD-bgp] quit
- 配置EBGP连接
# 配置RouterD。
[RouterD] bgp 10
[RouterD-bgp] peer 10.2.1.2 as-number 20
[RouterD-bgp] import-route direct
[RouterD-bgp] import-route ospf 1
[RouterD-bgp] quit
# 配置RouterE。
[RouterE] bgp 20
[RouterE-bgp] peer 10.2.1.1 as-number 10
[RouterE-bgp] ipv4-family unicast
[RouterE-bgp-af-ipv4] network 10.3.1.0 30
[RouterE-bgp-af-ipv4] quit
- 配置RouterC上OSPF协议的开销值
[RouterC] interface pos 1/0/0
[RouterC-GigabitEthernet1/0/0] ospf cost 2
[RouterC-GigabitEthernet1/0/0] quit
[RouterC] interface pos 2/0/0
[RouterC-GigabitEthernet2/0/0] ospf cost 2
[RouterC-GigabitEthernet2/0/0] quit
通过配置RouterC上OSPF协议的开销值为2,使得RouterA只选择RouterB作为到10.2.1.0网段的中间路由器,RouterC成为RouterB的备份路由器。
# 查看RouterA的路由表。从路由表中可以看出,通过BGP协议可以学习到目标网段10.3.1.0的路由,出接口是GigabitEthernet1/0/0。
[RouterA] display ip routing-tableRoute Flags: R - relay, D - download
to fib
------------------------------------------------------------------------------
Routing Tables: Public
Destinations : 16 Routes : 17
Destination/Mask Proto Pre Cost Flags NextHop Interface
1.1.1.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0
2.2.2.2/32 OSPF 10 3 D 10.1.1.2 GigabitEthernet1/0/0
4.4.4.0/24 IBGP 255 0 RD 4.4.4.4 GigabitEthernet1/0/0
4.4.4.4/32 OSPF 10 3 D 10.1.1.2 GigabitEthernet1/0/0
5.5.5.0/24 EBGP 255 0 RD 10.2.1.2 GigabitEthernet1/0/0
10.1.1.0/30 Direct 0 0 D 10.1.1.1 GigabitEthernet1/0/0
10.1.1.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0
10.1.1.2/32 Direct 0 0 D 10.1.1.2 GigabitEthernet1/0/0
10.1.2.0/30 Direct 0 0 D 10.1.2.1 GigabitEthernet2/0/0
10.1.2.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0
10.1.2.2/32 Direct 0 0 D 10.1.2.2 GigabitEthernet2/0/0
10.1.3.0/30 OSPF 10 2 D 10.1.1.2 GigabitEthernet1/0/0
10.1.3.1/32 IBGP 255 0 RD 4.4.4.4 GigabitEthernet1/0/0
10.1.4.0/30 OSPF 10 3 D 10.1.1.2 GigabitEthernet1/0/0
OSPF 10 3 D 10.1.2.2 GigabitEthernet2/0/0
10.1.4.1/32 IBGP 255 0 RD 4.4.4.4 GigabitEthernet1/0/0
10.2.1.0/30 EBGP 255 0 RD 4.4.4.4 GigabitEthernet1/0/0
10.2.1.2/32 EBGP 255 0 RD 4.4.4.4 GigabitEthernet1/0/0
10.3.1.0/30 EBGP 255 0 RD 4.4.4.4 GigabitEthernet1/0/0
# 查看RouterB的路由表。
[RouterB] display ip routing-tableRoute Flags: R - relay, D - download
to fib
------------------------------------------------------------------------------
Routing Tables: Public
Destinations : 15 Routes : 15
Destination/Mask Proto Pre Cost Flags NextHop Interface
2.2.2.2/32 Direct 0 0 D 127.0.0.1 InLoopBack0
1.1.1.1/32 OSPF 10 2 D 10.1.1.1 GigabitEthernet1/0/0
4.4.4.0/24 IBGP 255 0 RD 10.1.3.2 GigabitEthernet2/0/0
4.4.4.4/32 OSPF 10 2 D 10.1.3.2 GigabitEthernet2/0/0
5.5.5.0/24 EBGP 255 0 RD 10.2.1.2 GigabitEthernet2/0/0
10.1.1.0/30 Direct 0 0 D 10.1.1.2 GigabitEthernet1/0/0
10.1.1.1/32 Direct 0 0 D 10.1.1.1 GigabitEthernet1/0/0
10.1.1.2/32 Direct 0 0 D 127.0.0.1 InLoopBack0
10.1.2.0/30 OSPF 10 2 D 10.1.1.1 GigabitEthernet1/0/0
10.1.3.0/30 Direct 0 0 D 10.1.3.1 GigabitEthernet2/0/0
10.1.3.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0
10.1.3.2/32 Direct 0 0 D 10.1.3.2 GigabitEthernet2/0/0
10.1.4.0/30 OSPF 10 2 D 10.1.3.2 GigabitEthernet2/0/0
10.1.4.1/32 IBGP 255 0 RD 10.1.3.2 GigabitEthernet2/0/0
10.2.1.0/30 EBGP 255 0 RD 10.1.3.2 GigabitEthernet2/0/0
10.2.1.2/32 EBGP 255 0 RD 10.1.3.2 GigabitEthernet2/0/0
10.3.1.0/30 EBGP 255 0 RD 10.1.3.2 GigabitEthernet2/0/0
从路由表中可以看出,RouterB通过BGP协议可以学习到目标网段10.3.1.0的路由,出接口是GigabitEthernet2/0/0。通过OSPF协议可以学习到目标网段10.1.2.0和10.1.4.0的路由,路由开销都是2。
- 在RouterB上使能OSPF-BGP联动功能
[RouterB] ospf 1
[RouterB-ospf-1] stub-router on-startup
[RouterB-ospf-1] quit
[RouterB] quit
- 查看配置结果
# 重启路由器RouterB
在一般情况下,请勿使用该命令,因为它将导致网络工作在短时间内瘫痪,另外在重启路由器时,要确保路由器配置文件是否已经保存了。
<RouterB> reboot
System will reboot! Continue?[Y/N] y
# 查看RouterA的路由表。从路由表中可以看出,通过BGP协议可以学习到目标网段10.3.1.0的路由,出接口变为GigabitEthernet2/0/0。
[RouterA] display ip routing-tableRoute Flags: R - relay, D - download
to fib
------------------------------------------------------------------------------
Routing Tables: Public
Destinations : 17 Routes : 17
Destination/Mask Proto Pre Cost Flags NextHop Interface
1.1.1.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0
2.2.2.2/32 OSPF 10 4 D 10.1.2.2 GigabitEthernet2/0/0
4.4.4.0/24 IBGP 255 0 RD 4.4.4.4 GigabitEthernet2/0/0
4.4.4.4/32 OSPF 10 4 D 10.1.2.2 GigabitEthernet2/0/0
5.5.5.0/24 EBGP 255 0 RD 10.2.1.2 GigabitEthernet2/0/0
10.1.1.0/30 Direct 0 0 D 10.1.1.1 GigabitEthernet1/0/0
10.1.1.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0
10.1.1.2/32 Direct 0 0 D 10.1.1.2 GigabitEthernet1/0/0
10.1.2.0/30 Direct 0 0 D 10.1.2.1 GigabitEthernet2/0/0
10.1.2.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0
10.1.2.2/32 Direct 0 0 D 10.1.2.2 GigabitEthernet2/0/0
10.1.3.0/30 OSPF 10 2 D 10.1.1.2 GigabitEthernet1/0/0
10.1.3.1/32 IBGP 255 0 RD 4.4.4.4 GigabitEthernet2/0/0
10.1.4.0/30 OSPF 10 3 D 10.1.2.2 GigabitEthernet2/0/0
10.1.4.1/32 IBGP 255 0 RD 4.4.4.4 GigabitEthernet2/0/0
10.2.1.0/30 EBGP 255 0 RD 4.4.4.4 GigabitEthernet2/0/0
10.2.1.2/32 EBGP 255 0 RD 4.4.4.4 GigabitEthernet2/0/0
10.3.1.0/30 EBGP 255 0 RD 4.4.4.4 GigabitEthernet2/0/0
# 查看RouterB的路由表。从路由表中可以看出,由于IGP收敛速度比BGP快,所以路由表中暂时只有OSPF路由,并且开销值都已变为较大的数(≥65535)。
[RouterB] display ip routing-tableRoute Flags: R - relay, D - download
to fib
------------------------------------------------------------------------------
Routing Tables: Public
Destinations : 13 Routes : 13
Destination/Mask Proto Pre Cost Flags NextHop Interface
1.1.1.1/32 OSPF 10 65536 D 10.1.1.1 GigabitEthernet1/0/0
2.2.2.2/32 Direct 0 0 D 127.0.0.1 InLoopBack0
4.4.4.4/32 OSPF 10 65536 D 10.1.3.2 GigabitEthernet2/0/0
10.1.1.0/30 Direct 0 0 D 10.1.1.2 GigabitEthernet1/0/0
10.1.1.1/32 Direct 0 0 D 10.1.1.1 GigabitEthernet1/0/0
10.1.1.2/32 Direct 0 0 D 127.0.0.1 InLoopBack0
10.1.2.0/30 OSPF 10 65536 D 10.1.1.1 GigabitEthernet1/0/0
10.1.3.0/30 Direct 0 0 D 10.1.3.1 GigabitEthernet2/0/0
10.1.3.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0
10.1.3.2/32 Direct 0 0 D 10.1.3.2 GigabitEthernet2/0/0
10.1.4.0/30 OSPF 10 65536 D 10.1.3.2 GigabitEthernet2/0/0
127.0.0.0/8 Direct 0 0 D 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0
# 再次查看RouterB的路由表。
[RouterB] display ip routing-tableRoute Flags: R - relay, D - download
to fib
------------------------------------------------------------------------------
Routing Tables: Public
Destinations : 15 Routes : 15
Destination/Mask Proto Pre Cost Flags NextHop Interface
2.2.2.2/32 Direct 0 0 D 127.0.0.1 InLoopBack0
1.1.1.1/32 OSPF 10 2 D 10.1.1.1 GigabitEthernet1/0/0
4.4.4.0/24 IBGP 255 0 RD 10.1.3.2 GigabitEthernet2/0/0
4.4.4.4/32 OSPF 10 2 D 10.1.3.2 GigabitEthernet2/0/0
5.5.5.0/24 EBGP 255 0 RD 10.2.1.2 GigabitEthernet2/0/0
10.1.1.0/30 Direct 0 0 D 10.1.1.2 GigabitEthernet1/0/0
10.1.1.1/32 Direct 0 0 D 10.1.1.1 GigabitEthernet1/0/0
10.1.1.2/32 Direct 0 0 D 127.0.0.1 InLoopBack0
10.1.2.0/30 OSPF 10 2 D 10.1.1.1 GigabitEthernet1/0/0
10.1.3.0/30 Direct 0 0 D 10.1.3.1 GigabitEthernet2/0/0
10.1.3.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0
10.1.3.2/32 Direct 0 0 D 10.1.3.2 GigabitEthernet2/0/0
10.1.4.0/30 OSPF 10 2 D 10.1.3.2 GigabitEthernet2/0/0
10.1.4.1/32 IBGP 255 0 RD 10.1.3.2 GigabitEthernet2/0/0
10.2.1.0/30 EBGP 255 0 RD 10.1.3.2 GigabitEthernet2/0/0
10.2.1.2/32 EBGP 255 0 RD 10.1.3.2 GigabitEthernet2/0/0
10.3.1.0/30 EBGP 255 0 RD 10.1.3.2 GigabitEthernet2/0/0
从路由表中可以看出,当RouterB上的BGP完全收敛后,路由信息又恢复到重启前的内容。
配置文件
RouterA的配置文件
#
sysname RouterA
#
router id 1.1.1.1
#
interface pos1/0/0
undo shutdown
ip address 10.1.1.1 255.255.255.252
#
interface pos2/0/0
undo shutdown
ip address 10.1.2.1 255.255.255.252
#
interface LoopBack0
ip address 1.1.1.1 255.255.255.255
#
bgp 10
router-id 1.1.1.1
peer 2.2.2.2 as-number 10
peer 2.2.2.2 connect-interface LoopBack 0
peer 3.3.3.3 as-number 10
peer 3.3.3.3 connect-interface LoopBack 0
peer 4.4.4.4 as-number 10
peer 4.4.4.4 connect-interface LoopBack 0
#
ipv4-family unicast
undo synchronization
peer 2.2.2.2 enable
peer 3.3.3.3 enable
peer 4.4.4.4 enable
#
ospf 1
area 0.0.0.0
network 1.1.1.1 0.0.0.0
network 10.1.1.0 0.0.0.3
network 10.1.2.0 0.0.0.3
#
return
RouterB的配置文件
#
sysname RouterB
#
router id 2.2.2.2
#
interface pos1/0/0
undo shutdown
ip address 10.1.1.2 255.255.255.252
#
interface pos2/0/0
undo shutdown
ip address 10.1.3.1 255.255.255.252
#
interface LoopBack0
ip address 2.2.2.2 255.255.255.255
#
bgp 10
router-id 2.2.2.2
peer 1.1.1.1 as-number 10
peer 1.1.1.1 connect-interface LoopBack 0
peer 3.3.3.3 as-number 10
peer 3.3.3.3 connect-interface LoopBack 0
peer 4.4.4.4 as-number 10
peer 4.4.4.4 connect-interface LoopBack 0
#
ipv4-family unicast
undo synchronization
peer 1.1.1.1 enable
peer 3.3.3.3 enable
peer 4.4.4.4 enable
#
ospf 1
stub-router on-startup
area 0.0.0.0
network 10.1.1.0 0.0.0.3
network 10.1.3.0 0.0.0.3
network 2.2.2.2 0.0.0.0
#
return
RouterC的配置文件
#
sysname RouterC
#
router id 3.3.3.3
#
interface pos1/0/0
undo shutdown
ip address 10.1.4.1 255.255.255.252
ospf cost 2
#
interface pos2/0/0
undo shutdown
ip address 10.1.2.2 255.255.255.252
ospf cost 2
#
interface LoopBack0
ip address 3.3.3.3 255.255.255.255
#
bgp 10
router-id 3.3.3.3
peer 1.1.1.1 as-number 10
peer 1.1.1.1 connect-interface LoopBack 0
peer 2.2.2.2 as-number 10
peer 2.2.2.2 connect-interface LoopBack 0
peer 4.4.4.4 as-number 10
peer 4.4.4.4 connect-interface LoopBack 0
#
ipv4-family unicast
undo synchronization
peer 1.1.1.1 enable
peer 2.2.2.2 enable
peer 4.4.4.4 enable
#
ospf 1
area 0.0.0.0
network 10.1.2.0 0.0.0.3
network 10.1.4.0 0.0.0.3
network 3.3.3.3 0.0.0.0
#
return
RouterD的配置文件
#
sysname RouterD
#
router id 4.4.4.4
#
interface pos1/0/0
undo shutdown
ip address 10.1.4.2 255.255.255.252
#
interface pos2/0/0
undo shutdown
ip address 10.1.3.2 255.255.255.252
#
interface pos3/0/0
undo shutdown
ip address 10.2.1.1 255.255.255.252
#
interface LoopBack0
ip address 4.4.4.4 255.255.255.255
#
bgp 10
router-id 4.4.4.4
peer 10.2.1.2 as-number 20
peer 1.1.1.1 as-number 10
peer 1.1.1.1 connect-interface LoopBack 0
peer 2.2.2.2 as-number 10
peer 2.2.2.2 connect-interface LoopBack 0
peer 3.3.3.3 as-number 10
peer 3.3.3.3 connect-interface LoopBack 0
#
ipv4-family unicast
undo synchronization
import-route direct
import-route ospf 1
peer 2.2.2.2 enable
peer 1.1.1.1 enable
peer 5.5.5.5 enable
peer 10.2.1.2 enable
#
ospf 1
area 0.0.0.0
network 4.4.4.4 0.0.0.0
network 10.1.3.0 0.0.0.3
network 10.1.4.0 0.0.0.3
#
return
RouterE的配置文件
#
sysname RouterE
#
router id 5.5.5.5
#
interface pos1/0/0
undo shutdown
ip address 10.2.1.2 255.255.255.252
#
interface pos2/0/0
undo shutdown
ip address 10.3.1.1 255.255.255.252
#
interface LoopBack0
ip address 5.5.5.5 255.255.255.255
#
bgp 20
router-id 5.5.5.5
peer 10.2.1.1 as-number 10
#
ipv4-family unicast
undo synchronization
network 10.3.1.0 255.255.255.252
peer 10.2.1.1 enable
#
return

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