BGP条件通告功能

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已更新: 2020 年 6 月 15 日

文档 ID:215634

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简介

本文档介绍边界网关协议(BGP)条件通告功能，该功能提供对路由通告的额外控制，具体取决于BGP表中是否存在其他前缀。

先决条件

要求

Cisco 建议您了解以下主题：

独立于平台

使用的组件

本文档中的信息基于以下软件和硬件版本：

IOS
IOS-XE
ASR1000

本文档中的信息都是基于特定实验室环境中的设备编写的。本文档中使用的所有设备最初均采用原始（默认）配置。如果您的网络处于活动状态，请确保您了解所有命令的潜在影响。

配置

配置R1、R2和R3。此处给出配置。

网络图

配置

R1配置：

!
hostname R1
!
ip cef
!
interface Loopback0
ip address 1.1.1.1 255.255.255.255
! 
interface Loopback1
ip address 1.1.1.2 255.255.255.255
!
interface Loopback2
ip address 1.1.1.3 255.255.255.255
!
interface Loopback3
ip address 1.1.1.4 255.255.255.255
!
interface Loopback4
ip address 1.1.1.5 255.255.255.255
!
interface Loopback100
ip address 10.139.224.1 255.255.240.0
!
interface Ethernet0/0
ip address 10.10.12.1 255.255.255.0
!
router bgp 1
bgp log-neighbor-changes
neighbor 10.10.12.2 remote-as 2
!
address-family ipv4
network 0.0.0.0 route-map DEF
network 1.1.1.1 mask 255.255.255.255 route-map RM1
network 1.1.1.5 mask 255.255.255.255
redistribute connected route-map CUST
neighbor 10.10.12.2 activate
neighbor 10.10.12.2 send-community
neighbor 10.10.12.2 soft-reconfiguration inbound
exit-address-family
!
ip forward-protocol nd
! 
ip bgp-community new-format
ip route 0.0.0.0 0.0.0.0 Null0
!
ip prefix-list CUST seq 5 permit 10.139.224.0/20
!
ip prefix-list DEFAULT seq 5 permit 0.0.0.0/0
!
ip prefix-list PL1 seq 5 permit 1.1.1.1/32
!
route-map CUST permit 10
match ip address prefix-list CUST
set community 64671:501
!
route-map RM1 permit 10
match ip address prefix-list PL1
set community 64952:3008
!
route-map DEF permit 10
match ip address prefix-list DEFAULT
set community 64848:3011 65011:200 65013:200
!
end

R2配置：

!
hostname R2
!
ip cef
!
interface Loopback0
 ip address 2.2.2.2 255.255.255.255
!         
interface Ethernet0/0
 ip address 10.10.12.2 255.255.255.0
!
interface Ethernet0/1
 ip address 10.10.23.2 255.255.255.0
!
router bgp 2
 bgp log-neighbor-changes
 neighbor 10.10.12.1 remote-as 1
 neighbor 10.10.23.3 remote-as 3
 !
 address-family ipv4
  neighbor 10.10.12.1 activate
  neighbor 10.10.12.1 soft-reconfiguration inbound
  neighbor 10.10.23.3 activate
  neighbor 10.10.23.3 send-community
  neighbor 10.10.23.3 advertise-map ADV-MAP exist-map EXIST-MAP <<< This statement changes in non-exist-map
  neighbor 10.10.23.3 soft-reconfiguration inbound
 exit-address-family
!
ip forward-protocol nd
!
ip bgp-community new-format
ip community-list standard DEFAULT-ROUTE permit 65013:200
ip community-list standard DC1-ROUTES permit 64952:3008
ip community-list standard DC2-ROUTES permit 64671:501
ip community-list standard DC3-ROUTES permit 64950:3009
ip community-list standard DEFAULT-ROUTE-DENY deny 65013:200
!
!
ip prefix-list DEFAULT seq 5 permit 1.1.1.5/32
ip prefix-list DEFAULT seq 10 permit 1.1.1.1/32
!
ip prefix-list EXIST seq 5 permit 10.10.10.10/32
!
ip prefix-list DEFAULT-ROUTE seq 5 permit 0.0.0.0/0
!
ip prefix-list DEFAULT-ROUTE-DENY seq 5 deny 0.0.0.0/0
!
ip prefix-list IP1 seq 5 permit 10.139.224.0/20
!
ip prefix-list T2 seq 5 permit 1.1.1.5/32
!
route-map ADV-MAP permit 10
 match ip address prefix-list IP1
!
route-map ADV-MAP permit 20
 match community DC1-ROUTES DC2-ROUTES DC3-ROUTES
!
route-map EXIST-MAP permit 10
 description Verify Default Route from MDC-SWG
 match ip address prefix-list DEFAULT-ROUTE IP1
 match community DEFAULT-ROUTE
!
!
end

R3配置：

!
hostname R3
!
ip cef
!
interface Loopback0
 ip address 3.3.3.3 255.255.255.255
!
interface Ethernet0/1
 ip address 10.10.23.3 255.255.255.0
 shutdown
!
router bgp 3
 bgp log-neighbor-changes
 neighbor 10.10.23.2 remote-as 2
 !
 address-family ipv4
  neighbor 10.10.23.2 activate
  neighbor 10.10.23.2 send-community
  neighbor 10.10.23.2 soft-reconfiguration inbound
 exit-address-family
!         
ip forward-protocol nd
!
ip bgp-community new-format
!
!
end

验证

条件1:

如果BGP RIB中不存在默认路由，R2不应通告某些路由。
如果BGP RIB中存在默认路由，R2应通告所有路由。

使用exist-map

条件2:

如果BGP RIB中不存在默认路由，R2应通告所有路由。
如果BGP RIB中存在默认路由，R2不应通告某些路由。

使用非存在映射

R1#show ip bgp 
BGP table version is 7, local router ID is 10.139.224.1
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, 
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  0.0.0.0          0.0.0.0                  0         32768 i
 *>  1.1.1.1/32       0.0.0.0                  0         32768 i
 *>  1.1.1.5/32       0.0.0.0                  0         32768 i
 *>  10.139.224.0/20  0.0.0.0                  0         32768 ?

R2#show ip bgp 
BGP table version is 11, local router ID is 2.2.2.2
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, 
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  0.0.0.0          10.10.12.1               0             0 1 i
 *>  1.1.1.1/32       10.10.12.1               0             0 1 i
 *>  1.1.1.5/32       10.10.12.1               0             0 1 i
 *>  10.139.224.0/20  10.10.12.1               0             0 1 ?
R2#show ip bgp 0.0.0.0
BGP routing table entry for 0.0.0.0/0, version 9
Paths: (1 available, best #1, table default)
  Advertised to update-groups:
     1         
  Refresh Epoch 1
  1, (received & used)
    10.10.12.1 from 10.10.12.1 (10.139.224.1)
      Origin IGP, metric 0, localpref 100, valid, external, best
      Community: 64848:3011 65011:200 65013:200
      rx pathid: 0, tx pathid: 0x0

R2#show ip bgp neighbors 10.10.23.3 advertised-routes 
BGP table version is 11, local router ID is 2.2.2.2
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, 
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  0.0.0.0          10.10.12.1               0             0 1 i
 *>  1.1.1.1/32       10.10.12.1               0             0 1 i
 *>  1.1.1.5/32       10.10.12.1               0             0 1 i
 *>  10.139.224.0/20  10.10.12.1               0             0 1 ?

Total number of prefixes 4

Condition1 Verification:
========================
If default route is not present in BGP RIB, R2 should not advertise certain routes.
If default route is present in BGP RIB, R2 should advertise all the routes.
Use exist-map

R2's BGP Configuration:
=======================
R2#show running-config | sec bgp
router bgp 2
bgp log-neighbor-changes
neighbor 10.10.12.1 remote-as 1
neighbor 10.10.23.3 remote-as 3
!
address-family ipv4
neighbor 10.10.12.1 activate
neighbor 10.10.12.1 soft-reconfiguration inbound
neighbor 10.10.23.3 activate
neighbor 10.10.23.3 send-community
neighbor 10.10.23.3 advertise-map ADV-MAP exist-map EXIST-MAP
neighbor 10.10.23.3 soft-reconfiguration inbound
exit-address-family
ip bgp-community new-format


When Default route is removed from R2's BGP RIB:
================================================
*Mar 6 09:07:08.833: BGP(0): 10.10.12.1 rcv UPDATE about 0.0.0.0/0 -- withdrawn
*Mar 6 09:07:08.833: BGP(0): no valid path for 0.0.0.0/0
*Mar 6 09:07:08.833: BGP: topo global:IPv4 Unicast:base Remove_fwdroute for 0.0.0.0/0
*Mar 6 09:07:08.833: BGP(0): (base) 10.10.23.3 send unreachable (format) 0.0.0.0/0
*Mar 6 09:07:21.280: BPG(0): Condition EXIST-MAP changes to Withdraw
*Mar 6 09:07:21.353: BGP(0): net 1.1.1.1/32 matches ADV MAP ADV-MAP: bump version to 13
*Mar 6 09:07:21.353: BGP(0): net 10.139.224.0/20 matches ADV MAP ADV-MAP: bump version to 14
*Mar 6 09:07:21.362: BGP(0): Revise route installing 1 of 1 routes for 1.1.1.1/32 -> 10.10.12.1(global) to main IP table
*Mar 6 09:07:21.362: BGP(0): Revise route installing 1 of 1 routes for 10.139.224.0/20 -> 10.10.12.1(global) to main IP table
*Mar 6 09:07:38.933: BGP(0): (base) 10.10.23.3 send unreachable (format) 1.1.1.1/32
*Mar 6 09:07:38.933: BGP(0): (base) 10.10.23.3 send unreachable (format) 10.139.224.0/20

R2#show ip bgp neighbors 10.10.23.3 advertised-routes 
BGP table version is 14, local router ID is 2.2.2.2
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, 
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  1.1.1.5/32       10.10.12.1               0             0 1 i

Total number of prefixes 1 


When Default route is added back into R2's BGP RIB: 
===================================================
*Mar  6 09:15:22.883: BGP(0): 10.10.12.1 rcvd UPDATE w/ attr: nexthop 10.10.12.1, origin i, metric 0, merged path 1, AS_PATH , community 64848:3011 65011:200 65013:200
*Mar  6 09:15:22.883: BGP(0): 10.10.12.1 rcvd 0.0.0.0/0
*Mar  6 09:15:22.883: BGP(0): Revise route installing 1 of 1 routes for 0.0.0.0/0 -> 10.10.12.1(global) to main IP table
*Mar  6 09:15:22.883: BGP(0): (base) 10.10.23.3 send UPDATE (format) 0.0.0.0/0, next 10.10.23.2, metric 0, path 1
*Mar  6 09:16:21.759: BPG(0): Condition EXIST-MAP changes to Advertise
*Mar  6 09:16:21.759: BGP(0): net 1.1.1.1/32 matches ADV MAP ADV-MAP: bump version to 16
*Mar  6 09:16:21.759: BGP(0): net 10.139.224.0/20 matches ADV MAP ADV-MAP: bump version to 17
*Mar  6 09:16:21.768: BGP(0): Revise route installing 1 of 1 routes for 1.1.1.1/32 -> 10.10.12.1(global) to main IP table
*Mar  6 09:16:21.769: BGP(0): Revise route installing 1 of 1 routes for 10.139.224.0/20 -> 10.10.12.1(global) to main IP table
*Mar  6 09:16:21.769: BGP(0): (base) 10.10.23.3 send UPDATE (format) 1.1.1.1/32, next 10.10.23.2, metric 0, path 1
*Mar  6 09:16:21.769: BGP(0): (base) 10.10.23.3 send UPDATE (format) 10.139.224.0/20, next 10.10.23.2, metric 0, path 1

R2#show ip bgp neighbors 10.10.23.3 advertised-routes 
BGP table version is 17, local router ID is 2.2.2.2
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, 
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  0.0.0.0          10.10.12.1               0             0 1 i
 *>  1.1.1.1/32       10.10.12.1               0             0 1 i
 *>  1.1.1.5/32       10.10.12.1               0             0 1 i
 *>  10.139.224.0/20  10.10.12.1               0             0 1 ?

Total number of prefixes 4

Condition2 Verification:
=========================
If default route is not present in BGP RIB, R2 should advertise all the routes.
If default route is present in BGP RIB, R2 should not advertise certain routes.
Use non-exist-map

R2's BGP Configuration:
=======================
R2#show running-config | sec bgp
router bgp 2
bgp log-neighbor-changes
neighbor 10.10.12.1 remote-as 1
neighbor 10.10.23.3 remote-as 3
!
address-family ipv4
neighbor 10.10.12.1 activate
neighbor 10.10.12.1 soft-reconfiguration inbound
neighbor 10.10.23.3 activate
neighbor 10.10.23.3 send-community
neighbor 10.10.23.3 advertise-map ADV-MAP non-exist-map EXIST-MAP
neighbor 10.10.23.3 soft-reconfiguration inbound
exit-address-family
ip bgp-community new-format


When Default route is removed from R2's BGP RIB:
================================================
*Mar  6 09:21:24.445: BGP(0): 10.10.12.1 rcv UPDATE about 0.0.0.0/0 -- withdrawn
*Mar  6 09:21:24.445: BGP(0): no valid path for 0.0.0.0/0
*Mar  6 09:21:24.445: BGP: topo global:IPv4 Unicast:base Remove_fwdroute for 0.0.0.0/0
*Mar  6 09:21:24.445: BGP(0): (base) 10.10.23.3 send unreachable (format) 0.0.0.0/0
*Mar  6 09:22:22.050: BPG(0): Condition EXIST-MAP changes to Advertise
*Mar  6 09:22:22.050: BGP(0): net 1.1.1.1/32 matches ADV MAP ADV-MAP: bump version to 21
*Mar  6 09:22:22.050: BGP(0): net 10.139.224.0/20 matches ADV MAP ADV-MAP: bump version to 22
*Mar  6 09:22:22.060: BGP(0): Revise route installing 1 of 1 routes for 1.1.1.1/32 -> 10.10.12.1(global) to main IP table
*Mar  6 09:22:22.060: BGP(0): Revise route installing 1 of 1 routes for 10.139.224.0/20 -> 10.10.12.1(global) to main IP table
*Mar  6 09:22:22.060: BGP(0): (base) 10.10.23.3 send UPDATE (format) 1.1.1.1/32, next 10.10.23.2, metric 0, path 1
*Mar  6 09:22:22.060: BGP(0): (base) 10.10.23.3 send UPDATE (format) 10.139.224.0/20, next 10.10.23.2, metric 0, path 1

R2#show ip bgp neighbors 10.10.23.3 advertised-routes 
BGP table version is 22, local router ID is 2.2.2.2
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, 
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  1.1.1.1/32       10.10.12.1               0             0 1 i
 *>  1.1.1.5/32       10.10.12.1               0             0 1 i
 *>  10.139.224.0/20  10.10.12.1               0             0 1 ?

Total number of prefixes 3 


When Default route is added back into R2's BGP RIB:
=====================================================
*Mar  6 09:23:04.461: BGP(0): 10.10.12.1 rcvd UPDATE w/ attr: nexthop 10.10.12.1, origin i, metric 0, merged path 1, AS_PATH , community 64848:3011 65011:200 65013:200
*Mar  6 09:23:04.461: BGP(0): 10.10.12.1 rcvd 0.0.0.0/0
*Mar  6 09:23:04.461: BGP(0): Revise route installing 1 of 1 routes for 0.0.0.0/0 -> 10.10.12.1(global) to main IP table
*Mar  6 09:23:04.461: BGP(0): (base) 10.10.23.3 send UPDATE (format) 0.0.0.0/0, next 10.10.23.2, metric 0, path 1
*Mar  6 09:23:22.090: BPG(0): Condition EXIST-MAP changes to Withdraw
*Mar  6 09:23:22.090: BGP(0): net 1.1.1.1/32 matches ADV MAP ADV-MAP: bump version to 24
*Mar  6 09:23:22.090: BGP(0): net 10.139.224.0/20 matches ADV MAP ADV-MAP: bump version to 25
*Mar  6 09:23:22.103: BGP(0): Revise route installing 1 of 1 routes for 1.1.1.1/32 -> 10.10.12.1(global) to main IP table
*Mar  6 09:23:22.103: BGP(0): Revise route installing 1 of 1 routes for 10.139.224.0/20 -> 10.10.12.1(global) to main IP table
*Mar  6 09:23:35.248: BGP(0): (base) 10.10.23.3 send unreachable (format) 1.1.1.1/32
*Mar  6 09:23:35.248: BGP(0): (base) 10.10.23.3 send unreachable (format) 10.139.224.0/20

R2#show ip bgp neighbors 10.10.23.3 advertised-routes 
BGP table version is 25, local router ID is 2.2.2.2
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, 
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  0.0.0.0          10.10.12.1               0             0 1 i
 *>  1.1.1.5/32       10.10.12.1               0             0 1 i

Total number of prefixes 2

	存在映射状态	通告映射状态
如果存在默认路由。	条件匹配	通告
如果默认路由不存在。	条件不匹配	已撤消

	不存在映射状态	通告映射状态
如果存在默认路由。	条件匹配	退回
如果默认路由不存在。	条件不匹配	通告

故障排除

重要命令是debug ip bgp updates，它为您提供与BGP条件映射关联的路由映射的后端移动。在大型网络中，使用ACL运行条件调试。

注意：BGP扫描程序进程每60秒运行一次，因此，一旦我们获得exist-map/non-exist-map的更新，Advertise-map就需要60秒才能触发。

由思科工程师提供

Jaivik Shah
Cisco TAC Engineer

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