瞭解OSPF路由重分配到BGP

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已更新: 2026 年 9 月 8 日
文件 ID:5242

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簡介

本文件說明思科路由器將開放最短路徑優先 (OSPF) 重新分配至邊界閘道協定 (BGP) 的行為。

必要條件

需求

使用本文檔之前，思科建議您瞭解OSPF路由型別、BGP基礎知識和路由重分發。

採用元件

本文件所述內容不限於特定軟體和硬體版本。

note-icon

附註：本檔案中的範例使用Cisco IOS軟體命令語法。

本文中的資訊是根據特定實驗室環境內的裝置所建立。文中使用到的所有裝置皆從已清除（預設）的組態來啟動。如果您的網路運作中，請確保您瞭解任何指令可能造成的影響。

背景資訊

本技術說明解釋思科路由器上OSPF到BGP重分發的行為。RFC 1403文檔了OSPF和BGP之間互動的歷史指南。

OSPF路由有幾種型別：

  • 區域內 — 在多區域OSPF網路中，來自某一區域的路由被同一區域中的路由器視為區域內路由。在show ip route 命令輸出中，這些路由標籤為O。

  • 區域間 — 當路由通過OSPF區域邊界路由器(ABR)時，該路由稱為OSPF區域間路由。在show ip route命令輸出中，這些路由被標籤為O IA。

    區域內路由和區域間路由也稱為OSPF內部路由，因為它們代表源自OSPF域內的字首，而不是重分發到OSPF的路由。

  • External Type-2或External Type-1 — 重新分發到OSPF中的路由（如已連線、靜態或其他路由協定）稱為External Type-2或External Type-1。在show ip route命令輸出中，這些路由標籤為O E2或O E1。

  • NSSA External Type-2或NSSA External Type 1 — 將某個區域配置為非末節區域(NSSA)並將路由重分發到OSPF時，這些路由稱為NSSA External Type-2或NSSA External Type-1。在show ip route 命令輸出中，這些路由標籤為O N2或O N1。

解釋外部和NSSA第2類或1類之間的差異超出本文檔的範圍；有關詳細資訊，請參閱OSPF設計手冊。

預設行為是不將任何路由從OSPF重分發到BGP。必須配置重分發。在OSPF到BGP重分發期間，使用route-map命令過濾路由。要顯式選擇路由型別，請使用適用的match internal、match external或match nssa-external選項。如果不使用匹配選項，則預設情況下，redistribute ospf會重新分配OSPF內部路由。

網路設定

本文檔討論了五個主要的OSPF到BGP重分發案例。拓撲A適用於前四種情況。拓撲B適用於「將OSPF NSSA外部路由重分配到BGP」部分中所述的NSSA外部路由案例。


Redistribution OSPF to BGP Topology A將OSPF重新分發到BGP拓撲A

僅將OSPF內部（區域內和區域間）路由重分佈到BGP

如果將OSPF重分發到BGP而不使用關鍵字，則預設情況下僅將OSPF區域內路由和區域間路由重分發到BGP。要重分發OSPF Intra-area和Inter-area路由，請在路由器bgp下使用internal關鍵字和redistribute命令。

此路由器B(RTB)配置將OSPF內部字首10.2.2.0/24、10.108.1.0/24和10.108.2.0/24重新分發到BGP:

RTB 
hostname RTB
!
interface GigabitEthernet0/0
 ip address 10.3.3.1 255.255.255.0
 duplex auto
 speed auto
 media-type rj45
!
interface GigabitEthernet0/1
 ip address 10.2.2.3 255.255.255.0
 duplex auto
 speed auto
 media-type rj45 
! 
router ospf 1
 network 10.2.2.0 0.0.0.255 area 1
! 
router bgp 100 
redistribute ospf 1 

!-- This redistributes only OSPF intra-area and inter-area routes into BGP.  

neighbor 10.3.3.2 remote-as 200 
! 
end 

RTB#show ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area 
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
       a - application route
       + - replicated route, % - next hop override, p - overrides from PfR

Gateway of last resort is not set

      10.0.0.0/8 is variably subnetted, 6 subnets, 2 masks
C        10.2.2.0/24 is directly connected, GigabitEthernet0/1
L        10.2.2.3/32 is directly connected, GigabitEthernet0/1
C        10.3.3.0/24 is directly connected, GigabitEthernet0/0
L        10.3.3.1/32 is directly connected, GigabitEthernet0/0
O IA     10.108.1.0/24 [110/3] via 10.2.2.2, 00:08:38, GigabitEthernet0/1
O        10.108.2.0/24 [110/2] via 10.2.2.2, 00:39:13, GigabitEthernet0/1
O E2  192.168.1.0/24 [110/20] via 10.2.2.2, 00:07:39, GigabitEthernet0/1
O E1  192.168.2.0/24 [110/23] via 10.2.2.2, 00:07:38, GigabitEthernet0/1
RTB#

路由器B僅重新分配OSPF內部路由：

RTB#show ip bgp
BGP table version is 12, local router ID is 10.3.3.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, 
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, 
              x best-external, a additional-path, c RIB-compressed, 
              t secondary path, 
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *> 10.2.2.0/24 0.0.0.0 0 32768 ? *> 10.108.1.0/24 10.2.2.2 3 32768 ? *> 10.108.2.0/24 10.2.2.2 2 32768 ?
RTB#

路由器C從BGP獲知這些路由：

RTC#show ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area 
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
       a - application route
       + - replicated route, % - next hop override, p - overrides from PfR

Gateway of last resort is not set

      10.0.0.0/8 is variably subnetted, 5 subnets, 2 masks
B        10.2.2.0/24 [20/0] via 10.3.3.1, 00:07:07
C        10.3.3.0/24 is directly connected, GigabitEthernet0/0
L        10.3.3.2/32 is directly connected, GigabitEthernet0/0
B        10.108.1.0/24 [20/3] via 10.3.3.1, 00:07:07
B        10.108.2.0/24 [20/2] via 10.3.3.1, 00:07:07
RTC#
RTC#show ip bgp
BGP table version is 8, local router ID is 10.3.3.2
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, 
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, 
              x best-external, a additional-path, c RIB-compressed, 
              t secondary path, 
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *> 10.2.2.0/24 10.3.3.1 0 0 100 ? *> 10.108.1.0/24 10.3.3.1 3 0 100 ? *> 10.108.2.0/24 10.3.3.1 2 0 100 ?
RTC#

僅將OSPF外部（型別1和2）路由重分發到BGP

若要將OSPF外部路由重分發到BGP，請在router bgp下使用帶有redistribute命令的external關鍵字。使用external關鍵字時，有三個選擇：

  • 重新分發外部型別1和型別2（預設）

  • Redistribute型別1

  • Redistribute型別2


按如下所述在配置模式下輸入命令：

RTB(config)#router bgp 100
RTB(config-router)#redistribute ospf 1 match external

此路由器B配置僅重新分配OSPF外部路由，包括第1類路由和第2類路由：

RTB 
hostname RTB
!
interface GigabitEthernet0/0
 ip address 10.3.3.1 255.255.255.0
 duplex auto
 speed auto
 media-type rj45
!
interface GigabitEthernet0/1
 ip address 10.2.2.3 255.255.255.0
 duplex auto
 speed auto
 media-type rj45 
! 
router ospf 1
 network 10.2.2.0 0.0.0.255 area 1 
! 
router bgp 100 
 redistribute ospf 1 match external 1 external 2 

!--- This redistributes ONLY OSPF External routes, but both type-1 and type-2.  

neighbor 10.3.3.2 remote-as 200 
! 
end

附註：配置顯示輸入的命令是redistribute ospf 1 match external。這是正常現象，因為OSPF會在配置中自動附加外部1 external 2。它匹配OSPF外部1路由和外部2路由，並將兩個路由重分發到BGP。

路由器B僅重新分配OSPF外部路由：

RTB#show ip bgp
BGP table version is 25, local router ID is 10.3.3.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, 
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, 
              x best-external, a additional-path, c RIB-compressed, 
              t secondary path, 
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>   192.168.1.0      10.2.2.2                20         32768 ?
 *>   192.168.2.0      10.2.2.2                23         32768 ?
RTB#

路由器C從BGP獲知這兩條OSPF外部路由：

RTC#show ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area 
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
       a - application route
       + - replicated route, % - next hop override, p - overrides from PfR

Gateway of last resort is not set

      10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        10.3.3.0/24 is directly connected, GigabitEthernet0/0
L        10.3.3.2/32 is directly connected, GigabitEthernet0/0
B     192.168.1.0/24 [20/20] via 10.3.3.1, 00:02:16
B     192.168.2.0/24 [20/23] via 10.3.3.1, 00:02:16

RTC#show ip bgp
BGP table version is 21, local router ID is 10.3.3.2
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, 
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, 
              x best-external, a additional-path, c RIB-compressed, 
              t secondary path, 
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *> 192.168.1.0 10.3.3.1 20 0 100 ? *> 192.168.2.0 10.3.3.1 23 0 100 ?
RTC#

僅將OSPF外部第1類或第2類路由重分發到BGP

要僅重分發OSPF外部第1類路由，請在路由器B的router bgp 100下輸入以下命令：

RTB(config)#router bgp 100 
RTB(config-router)#redistribute ospf 1 match external 1

使用先前的設定，路由器B(RTB)BGP表顯示路由器B只會將外部第1類路由重分佈到BGP，而所有其他OSPF路由不會重分佈到BGP:

RTB#show ip bgp
BGP table version is 28, local router ID is 10.3.3.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, 
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, 
              x best-external, a additional-path, c RIB-compressed, 
              t secondary path, 
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>   192.168.2.0      10.2.2.2                23         32768 ?
RTB#

要僅重分發OSPF外部第2類路由，請在路由器B的router bgp 100下輸入以下命令：

RTB(config)#router bgp 100 
RTB(config-router)#redistribute ospf 1 match external 2

將OSPF內部和外部路由重分發到BGP

在這種情況下，OSPF內部路由以及型別1和型別2的OSPF外部路由會使用內部和外部匹配選項重新分發到BGP，如以下路由器B配置所示：

RTB 
hostname RTB
!
interface GigabitEthernet0/0
 ip address 10.3.3.1 255.255.255.0
 duplex auto
 speed auto
 media-type rj45
!
interface GigabitEthernet0/1
 ip address 10.2.2.3 255.255.255.0
 duplex auto
 speed auto
 media-type rj45 
! 
router ospf 1
network 10.2.2.0 0.0.0.255 area 1 
! 
router bgp 100
 redistribute ospf 1 match internal external 1 external 2 

!--- This redistributes OSPF internal and external type 1 & 2 routes into BGP.  

neighbor 10.3.3.2 remote-as 200 
! 
end


同樣，在配置中，external替換為external 1 external 2。這是正常現象，除非您指定要重分佈到BGP中的特定外部路由。更改配置後，路由器B會重新分配選定的內部路由和外部路由，路由器C通過BGP獲取這些路由：

RTB#show ip bgp
BGP table version is 6, local router ID is 10.3.3.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, 
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, 
              x best-external, a additional-path, c RIB-compressed, 
              t secondary path, 
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *> 10.2.2.0/24 0.0.0.0 0 32768 ? *> 10.108.1.0/24 10.2.2.2 3 32768 ? *> 10.108.2.0/24 10.2.2.2 2 32768 ? *> 192.168.1.0 10.2.2.2 20 32768 ? *> 192.168.2.0 10.2.2.2 23 32768 ?
RTB# RTC#show ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area 
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
       a - application route
       + - replicated route, % - next hop override, p - overrides from PfR

Gateway of last resort is not set

      10.0.0.0/8 is variably subnetted, 5 subnets, 2 masks
B 10.2.2.0/24 [20/0] via 10.3.3.1, 00:03:27
C        10.3.3.0/24 is directly connected, GigabitEthernet0/0
L        10.3.3.2/32 is directly connected, GigabitEthernet0/0
B 10.108.1.0/24 [20/3] via 10.3.3.1, 00:03:27 B 10.108.2.0/24 [20/2] via 10.3.3.1, 00:03:27 B 192.168.1.0/24 [20/20] via 10.3.3.1, 00:03:27 B 192.168.2.0/24 [20/23] via 10.3.3.1, 00:03:27
RTC#

將OSPF NSSA外部路由重分發到BGP

這是一種特殊情況，其中只有NSSA路由重新分發到BGP中。此案例與僅重分佈到BGP中的OSPF外部（型別1和型別2）路由一節中描述的情況非常相似。唯一的區別是OSPF現在匹配NSSA外部路由，而不是僅匹配外部路由。路由器B的路由表顯示了以下OSPF NSSA外部路由：

RTB#show ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area 
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
       a - application route
       + - replicated route, % - next hop override, p - overrides from PfR

Gateway of last resort is not set

      10.0.0.0/8 is variably subnetted, 6 subnets, 2 masks
C        10.2.2.0/24 is directly connected, GigabitEthernet0/1
L        10.2.2.3/32 is directly connected, GigabitEthernet0/1
C        10.3.3.0/24 is directly connected, GigabitEthernet0/0
L        10.3.3.1/32 is directly connected, GigabitEthernet0/0
O IA     10.108.1.0/24 [110/3] via 10.2.2.2, 00:05:00, GigabitEthernet0/1
O        10.108.2.0/24 [110/2] via 10.2.2.2, 00:05:00, GigabitEthernet0/1
O N2  192.168.1.0/24 [110/20] via 10.2.2.1, 00:10:14, GigabitEthernet0/1
O N1  192.168.2.0/24 [110/22] via 10.2.2.2, 00:03:43, GigabitEthernet0/1
RTB#

以下網路圖是適用於此案例的：

Redistribution OSPF to BGP Topology B將OSPF重新分發到BGP拓撲B

網路圖顯示，路由器B同時收到OSPF N1和N2路由。如果僅使用nssa-external關鍵字，則預設行為是重分發N1和N2路由。此組態允許RTB將OSPF N2(192.168.1.0/24)和OSPF N1(192.168.2.0/24)路由重分發到BGP:

RTB 
hostname RTB
!
interface GigabitEthernet0/0
 ip address 10.3.3.1 255.255.255.0
 duplex auto
 speed auto
 media-type rj45
!
interface GigabitEthernet0/1
 ip address 10.2.2.3 255.255.255.0
 duplex auto
 speed auto
 media-type rj45 
! 
router ospf 1
 area 1 nssa network 10.2.2.0 0.0.0.255 area 1
!
router bgp 100 
 redistribute ospf 1 match nssa-external 1 nssa-external 2

!--- This redistributes only OSPF NSSA-external routes Type-1 and Type-2 into BGP.

neighbor 10.3.3.2 remote-as 200
!
end

附註：與OSPF外部配置類似，先前的配置顯示match nssa-external 1 nssa-external 2，輸入的命令為redistribute ospf 1 match nssa-external。這是正常現象，因為OSPF會在配置中自動附加nssa-external 1 nssa-external 2。它匹配OSPF N1和OSPF N2路由，並將兩個路由重分發到BGP。

在路由器B上更改配置後，它會重新分配OSPF NSSA外部路由，而路由器C從BGP獲取OSPF NSSA外部路由：

RTB#show ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area 
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
       a - application route
       + - replicated route, % - next hop override, p - overrides from PfR

Gateway of last resort is not set

      10.0.0.0/8 is variably subnetted, 6 subnets, 2 masks
C        10.2.2.0/24 is directly connected, GigabitEthernet0/1
L        10.2.2.3/32 is directly connected, GigabitEthernet0/1
C        10.3.3.0/24 is directly connected, GigabitEthernet0/0
L        10.3.3.1/32 is directly connected, GigabitEthernet0/0
O IA     10.108.1.0/24 [110/3] via 10.2.2.2, 00:09:40, GigabitEthernet0/1
O        10.108.2.0/24 [110/2] via 10.2.2.2, 00:09:40, GigabitEthernet0/1
O N2  192.168.1.0/24 [110/20] via 10.2.2.1, 00:14:54, GigabitEthernet0/1
O N1  192.168.2.0/24 [110/22] via 10.2.2.2, 00:08:23, GigabitEthernet0/1
RTB#
RTB#show ip bgp
BGP table version is 17, local router ID is 10.3.3.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, 
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, 
              x best-external, a additional-path, c RIB-compressed, 
              t secondary path, 
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *> 192.168.1.0 10.2.2.1 20 32768 ? *> 192.168.2.0 10.2.2.2 22 32768 ?
RTB# RTC#show ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area 
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
       a - application route
       + - replicated route, % - next hop override, p - overrides from PfR

Gateway of last resort is not set

      10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        10.3.3.0/24 is directly connected, GigabitEthernet0/0
L        10.3.3.2/32 is directly connected, GigabitEthernet0/0
B 192.168.1.0/24 [20/20] via 10.3.3.1, 00:01:29 B 192.168.2.0/24 [20/22] via 10.3.3.1, 00:01:29
RTC# 
RTC#show ip bgp
BGP table version is 41, local router ID is 10.3.3.2
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, 
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, 
              x best-external, a additional-path, c RIB-compressed, 
              t secondary path, 
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *> 192.168.1.0 10.3.3.1 20 0 100 ? *> 192.168.2.0 10.3.3.1 22 0 100 ?
RTC#

與OSPF外部路由一樣，要僅重分發OSPF N1路由，請在路由器B的路由器BGP 100下輸入以下命令：

RTB(config)#router bgp 100 
RTB(config-router)#redistribute ospf 1 match nssa-external 1 

!--- This redistributes only OSPF NSSA-external Type-1 routes into BGP.

要僅重新分配OSPF N2路由，請在路由器B的router bgp 100下輸入以下命令：

RTB(config)#router bgp 100  
RTB(config-router)#redistribute ospf 1 match nssa-external 2 

!--- This redistributes only OSPF NSSA-external Type-2 routes into BGP.

附註：路由對映還可用於將OSPF第1類或第2類路由重分發到BGP。

修改OSPF中的重分發選項

瞭解連續配置更改如何改變配置非常重要。帶有match選項的新命令不會覆蓋上一個命令，但會新增到該命令中。下一個示例說明配置命令序列如何影響重分發：

R4#configure terminal
R4(config)#router bgp 100
R4(config-router)#redistribute ospf 1 match internal
R4(config-router)#^Z

!--- Initially, you redistribute internal OSPF routes into BGP 100.

R4#show run | include redistribute ospf
 redistribute ospf 1 match internal
R4#configure terminal
R4(config)#router bgp 100
R4(config-router)#redistribute ospf 1 match external
R4(config-router)#^Z

!--- With this second command, you tell BGP to also redistribute external OSPF routes.

R4#show run | include redistribute ospf
 redistribute ospf 1 match internal external 1 external 2
R4#
R4#configure terminal
R4(config)#router bgp 100
R4(config-router)#no redistribute ospf 1 match external 2
R4(config-router)#^Z

!--- With this no command, you only disable the redistribution of external type 2 into BGP. 
!--- All other types of routes previously configured remain.

R4#show run | include redistribute ospf
 redistribute ospf 1 match internal external 1
 
!--- As you can see, internal and external type 1 remain.

R4#configure terminal
R4(config)#router bgp 100
R4(config-router)#no redistribute ospf 1 match internal external 1
R4(config-router)#^Z 

!--- This no command removes all explicit match options but does not disable redistribution 
!--- The remaining redistribute ospf 1 command uses the default behavior and redistributes 
!--- internal routes only.

R4#show run | include redistribute ospf
 redistribute ospf 1
R4#configure terminal
R4(config)#router bgp 100
R4(config-router)#no redistribute ospf 1 

!--- Use no redistribute ospf  command to disable OSPF-to-BGP redistribution completely.

R4(config-router)# ^Z
R4#show run | include redistribute ospf
R4#

無法將iBGP獲知的路由重分發到IGP

路由重分佈將通過一個協定獲知的路由傳播到另一個路由協定中。將BGP重分發到IGP時，預設情況下只重分發eBGP獲知的路由。路由器上已知的iBGP獲知的路由不會引入到IGP中，以防止產生路由環路。

預設情況下，iBGP重分發到IGP是禁用的。運行bgp redistribute-internal 命令以啟用iBGP路由重分配到IGP。需要採取預防措施，才能使用路由對映將特定路由重分配到IGP中。

將iBGP路由重分發到OSPF的示例配置如下所示：

Router(config)#router bgp 65345 
Router(config-router)#bgp redistribute-internal
!
Router(config)#router ospf 100
Router(config-router)#redistribute bgp 65345 subnets
caution-icon

注意：將iBGP獲知的路由重分發到IGP中會在自治系統內建立路由環路。僅重新分髮帶有路由對映的顯式批准的字首。

將OSPF預設路由重分發到BGP

要將OSPF獲取的預設路由重分發到BGP，請在路由對映中僅允許0.0.0.0/0，將路由對映應用到OSPF重分發，並啟用使用default-information originate重分發預設路由：

!
route-map map_default_only permit 10
 match ip address acl_default_only
!
ip access-list standard acl_default_only
 permit 0.0.0.0
!
router bgp 64601
 redistribute ospf 1 route-map map_default_only
 default-information originate
!

!--- Distributes the default route in bgp

network 0.0.0.0命令是單獨的發起方法，需要在路由表中提供準確的預設路由：

!
router bgp 64601
network 0.0.0.0
!

設定後，使用show ip bgp 0.0.0.0驗證預設路由，並使用show ip bgp neighbors <neighbor-address> advertised-routes驗證其通告。

note-icon

附註：BGP通常不重置會話就通告新路由。要請求即時、無中斷的更新交換，請運行clear ip bgp * soft命令。此命令用於保持BGP會話的建立。

相關資訊

修訂記錄

修訂 發佈日期 意見
3.0
08-Sep-2026
重新認證 — 更新的SEO和格式
2.0
22-Apr-2025
標題、標題和格式。
1.0
11-Oct-2001
初始版本
TAC Authored

由思科工程師貢獻

  • Julio Jimenez
    Cisco Project Manager

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