在Nexus 9000上配置BGP路由反射器

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已更新: 2024 年 2 月 6 日

文档 ID:221639

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简介

本文档介绍在Nexus 9000系列上配置边界网关协议(BGP)路由反射器的过程。

先决条件

要求

Cisco 建议您了解以下主题：

Nexus交换机
调试输出中显示“BGP

使用的组件

本文档不限于特定的软件和硬件版本。

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。如果您的网络处于生产状态，请确保您了解计划应用的任何命令的潜在影响。

背景信息

BGP用于避免路由环路的机制是通过将自己的自治系统编号(ASN)添加到AS PATH属性中。对于IBGP拓扑，更新不会修改AS-PATH属性，因为它们属于同一ASN，这可能会导致路由环路。

如果从IBGP对等体收到BGP前缀，则无法将此前缀通告到另一个IBGP邻居。 BGP使用其水平分割规则来防止同一ASN内的环路。

此规则强制您使用全网状拓扑与每个IBGP邻居交换前缀。对于具有全网状场景的大型网络，由于它使用过多资源创建对等网络，因此不能进行扩展。

iBGP的全网状拓扑的替代方案包括：

路由反射
联盟

本文档仅重点介绍BGP路由反射器的用法。

使用路由反射器可以克服全网状限制。路由反射器是AS（自治系统）内的指定设备，它将iBGP前缀反射到同一AS中的其他路由器。

配置

要检查BGP路由反射器配置指南，请参阅配置高级BGP

网络图

BGP Route Reflector Nexus

在此图中，Nexus R2、Nexus R3、Nexus 4、Nexus R5和Nexus R6建立了iBGP邻居关系。而且，Nexus R1和Nexus R5建立了eBGP邻居关系。

目标

将Nexus R1生成的网络交换到同一ASN网络中的所有65000。

初始验证

Nexus R1执行前缀通告：

R1# show ip bgp 
BGP routing table information for VRF default, address family IPv4 Unicast
BGP table version is 78, Local Router ID is 192.168.1.1
Status: s-suppressed, x-deleted, S-stale, d-dampened, h-history, *-valid, >-best
Path type: i-internal, e-external, c-confed, l-local, a-aggregate, r-redist, I-i
njected
Origin codes: i - IGP, e - EGP, ? - incomplete, | - multipath, & - backup, 2 - b
est2

   Network            Next Hop            Metric     LocPrf     Weight Path
*>r192.168.1.0/30     0.0.0.0                  0        100      32768 ?
*>r192.168.2.0/30     0.0.0.0                  0        100      32768 ?
*>r192.168.3.0/30     0.0.0.0                  0        100      32768 ?
*>r192.168.4.0/30     0.0.0.0                  0        100      32768 ?
*>r192.168.5.0/30     0.0.0.0                  0        100      32768 ?

R1#

Nexus R5收到来自Nexus R1的通告，Nexus R1是eBGP会话。

Nexus R5 

R5# show ip bgp 
BGP routing table information for VRF default, address family IPv4 Unicast
BGP table version is 123, Local Router ID is 172.16.1.2
Status: s-suppressed, x-deleted, S-stale, d-dampened, h-history, *-valid, >-best
Path type: i-internal, e-external, c-confed, l-local, a-aggregate, r-redist, I-injected
Origin codes: i - IGP, e - EGP, ? - incomplete, | - multipath, & - backup, 2 - best2

   Network            Next Hop            Metric     LocPrf     Weight Path
*>r10.1.1.4/30        0.0.0.0                  0        100      32768 ?
*>r10.1.1.8/30        0.0.0.0                  0        100      32768 ?
*>r172.16.1.0/30      0.0.0.0                  0        100      32768 ?
*>e192.168.1.0/30     172.16.1.1               0                     0 64512 ?
*>e192.168.2.0/30     172.16.1.1               0                     0 64512 ?
*>e192.168.3.0/30     172.16.1.1               0                     0 64512 ?
*>e192.168.4.0/30     172.16.1.1               0                     0 64512 ?
*>e192.168.5.0/30     172.16.1.1               0                     0 64512 ?

R5#

Nexus R5向其iBGP对等体Nexus R2和R6通告前缀。

R2# show ip bgp 
BGP routing table information for VRF default, address family IPv4 Unicast
BGP table version is 33, Local Router ID is 10.1.1.6
Status: s-suppressed, x-deleted, S-stale, d-dampened, h-history, *-valid, >-best
Path type: i-internal, e-external, c-confed, l-local, a-aggregate, r-redist, I-i
njected
Origin codes: i - IGP, e - EGP, ? - incomplete, | - multipath, & - backup, 2 - b
est2

   Network            Next Hop            Metric     LocPrf     Weight Path
*>i10.1.1.4/30        10.1.1.5                 0        100          0 ?
*>i10.1.1.8/30        10.1.1.5                 0        100          0 ?
*>i172.16.1.0/30      10.1.1.5                 0        100          0 ?
*>i192.168.1.0/30     172.16.1.1               0        100          0 64512 ?
*>i192.168.2.0/30     172.16.1.1               0        100          0 64512 ?
*>i192.168.3.0/30     172.16.1.1               0        100          0 64512 ?
*>i192.168.4.0/30     172.16.1.1               0        100          0 64512 ?
*>i192.168.5.0/30     172.16.1.1               0        100          0 64512 ?

R2#

R6# show ip bgp 
BGP routing table information for VRF default, address family IPv4 Unicast
BGP table version is 33, Local Router ID is 10.1.1.10
Status: s-suppressed, x-deleted, S-stale, d-dampened, h-history, *-valid, >-best
Path type: i-internal, e-external, c-confed, l-local, a-aggregate, r-redist, I-injected
Origin codes: i - IGP, e - EGP, ? - incomplete, | - multipath, & - backup, 2 - best2

   Network            Next Hop            Metric     LocPrf     Weight Path
*>i10.1.1.4/30        10.1.1.9                 0        100          0 ?
*>i10.1.1.8/30        10.1.1.9                 0        100          0 ?
*>i172.16.1.0/30      10.1.1.9                 0        100          0 ?
*>i192.168.1.0/30     172.16.1.1               0        100          0 64512 ?
*>i192.168.2.0/30     172.16.1.1               0        100          0 64512 ?
*>i192.168.3.0/30     172.16.1.1               0        100          0 64512 ?
*>i192.168.4.0/30     172.16.1.1               0        100          0 64512 ?
*>i192.168.5.0/30     172.16.1.1               0        100          0 64512 ?

R6#

根据环路避免规则，BGP不会向其他iBGP对等体通告iBGP对等体获取的任何前缀。

R2# show ip bgp neighbors 10.1.2.2 advertised-routes 

Peer 10.1.2.2 routes for address family IPv4 Unicast:
BGP table version is 88, Local Router ID is 10.150.0.1
Status: s-suppressed, x-deleted, S-stale, d-dampened, h-history, *-valid, >-best
Path type: i-internal, e-external, c-confed, l-local, a-aggregate, r-redist, I-i
njected
Origin codes: i - IGP, e - EGP, ? - incomplete, | - multipath, & - backup, 2 - b
est2

   Network            Next Hop            Metric     LocPrf     Weight Path
*>r10.1.1.4/30        0.0.0.0                  0        100      32768 ?
*>r10.1.2.0/30        0.0.0.0                  0        100      32768 ?
*>r10.1.2.4/30        0.0.0.0                  0        100      32768 ?
*>r10.1.2.8/30        0.0.0.0                  0        100      32768 ?
*>r10.150.0.0/30      0.0.0.0                  0        100      32768 ?

R2#

Nexus R3和Nexus R4不会接收Nexus R1生成的前缀。

R3# show ip bgp 
BGP routing table information for VRF default, address family IPv4 Unicast
BGP table version is 28, Local Router ID is 10.100.100.1
Status: s-suppressed, x-deleted, S-stale, d-dampened, h-history, *-valid, >-best
Path type: i-internal, e-external, c-confed, l-local, a-aggregate, r-redist, I-injected
Origin codes: i - IGP, e - EGP, ? - incomplete, | - multipath, & - backup, 2 - best2

   Network            Next Hop            Metric     LocPrf     Weight Path
*>l10.100.100.0/24    0.0.0.0                           100      32768 i

R4# show ip bgp 
BGP routing table information for VRF default, address family IPv4 Unicast
BGP table version is 6, Local Router ID is 10.200.200.1
Status: s-suppressed, x-deleted, S-stale, d-dampened, h-history, *-valid, >-best
Path type: i-internal, e-external, c-confed, l-local, a-aggregate, r-redist, I-injected
Origin codes: i - IGP, e - EGP, ? - incomplete, | - multipath, & - backup, 2 - best2

   Network            Next Hop            Metric     LocPrf     Weight Path
*>l10.200.200.0/24    0.0.0.0                           100      32768 i

R4#

配置

对于上述拓扑，要转换为路由反射器的选定设备是Nexus R2和Nexus R6，因为这些设备连接到同一ASN中的所有iBGP对等体。

注意：路由反射器配置导致重置每个修改的bgp对等体。此配置必须在维护窗口下完成。

注：通过拓扑设计，Nexus R2和R6成为ASN网络的路由反射65000。

Nexus R1

R1# show run bgp 

!Command: show running-config bgp
!Running configuration last done at: Wed Jan 31 02:43:31 2024
!Time: Wed Jan 31 23:24:28 2024

version 10.2(5) Bios:version 05.47
feature bgp

router bgp 64512
  address-family ipv4 unicast
    redistribute direct route-map REDISTRIBUTE_LOCAL
  neighbor 172.16.1.2
    remote-as 65000
    address-family ipv4 unicast


R1#

Nexus R2

R2# show run bgp 

!Command: show running-config bgp
!Running configuration last done at: Wed Jan 31 03:10:49 2024
!Time: Wed Jan 31 23:24:15 2024

version 10.2(5) Bios:version 05.47 
feature bgp

router bgp 65000
  cluster-id 10.150.0.1
  address-family ipv4 unicast
    redistribute direct route-map ALLOW
  neighbor 10.1.1.5
    remote-as 65000
    address-family ipv4 unicast
      route-reflector-client
  neighbor 10.1.2.2
    remote-as 65000
    address-family ipv4 unicast
      route-reflector-client
  neighbor 10.1.2.6
    remote-as 65000
    address-family ipv4 unicast
      route-reflector-client
  neighbor 10.1.2.10
    remote-as 65000
    address-family ipv4 unicast
      route-reflector-client


R2#

Nexus R3

R3# show run bgp 

!Command: show running-config bgp
!Running configuration last done at: Wed Jan 31 02:49:05 2024
!Time: Wed Jan 31 23:10:07 2024

version 10.2(5) Bios:version 05.47 
feature bgp

router bgp 65000
  address-family ipv4 unicast
    network 10.100.100.0/24
  neighbor 10.1.2.5
    remote-as 65000
    address-family ipv4 unicast
  neighbor 10.1.3.5
    remote-as 65000
    address-family ipv4 unicast


R3#

Nexus R4

R4# show run bgp 

!Command: show running-config bgp
!Running configuration last done at: Wed Jan 31 02:56:11 2024
!Time: Wed Jan 31 23:00:44 2024

version 10.2(5) Bios:version 05.47 
feature bgp

router bgp 65000
  address-family ipv4 unicast
    network 10.200.200.0/24
  neighbor 10.1.2.1
    remote-as 65000
    address-family ipv4 unicast
  neighbor 10.1.3.1
    remote-as 65000
    address-family ipv4 unicast


R4#

Nexus R5

R5# show run bgp 

!Command: show running-config bgp
!Running configuration last done at: Wed Jan 31 02:48:38 2024
!Time: Wed Jan 31 23:24:15 2024

version 10.2(5) Bios:version 05.47 
feature bgp

router bgp 65000
  address-family ipv4 unicast
    redistribute direct route-map ALLOW
  neighbor 10.1.1.6
    remote-as 65000
    address-family ipv4 unicast
  neighbor 10.1.1.10
    remote-as 65000
    address-family ipv4 unicast
  neighbor 172.16.1.1
    remote-as 64512
    address-family ipv4 unicast


R5#

Nexus R6

R6# show run bgp 

!Command: show running-config bgp
!Running configuration last done at: Wed Jan 31 03:12:40 2024
!Time: Wed Jan 31 23:24:18 2024

version 10.2(5) Bios:version 05.47
feature bgp

router bgp 65000
  cluster-id 10.160.0.1
  address-family ipv4 unicast
    redistribute direct route-map ALLOW
  neighbor 10.1.1.9
    remote-as 65000
    address-family ipv4 unicast
      route-reflector-client
  neighbor 10.1.2.9
    remote-as 65000
    address-family ipv4 unicast
      route-reflector-client
  neighbor 10.1.3.2
    remote-as 65000
    address-family ipv4 unicast
      route-reflector-client
  neighbor 10.1.3.6
    remote-as 65000
    address-family ipv4 unicast
      route-reflector-client


R6#

验证

将Nexus R2和Nexus R6配置为路由反射器后，前缀将通告给iBGP对等体。 .

R2# show ip bgp neighbors 10.1.2.2 advertised-routes 

Peer 10.1.2.2 routes for address family IPv4 Unicast:
BGP table version is 22, Local Router ID is 10.150.0.1
Status: s-suppressed, x-deleted, S-stale, d-dampened, h-history, *-valid, >-best
Path type: i-internal, e-external, c-confed, l-local, a-aggregate, r-redist, I-i
njected
Origin codes: i - IGP, e - EGP, ? - incomplete, | - multipath, & - backup, 2 - b
est2

   Network            Next Hop            Metric     LocPrf     Weight Path
*>r10.1.1.4/30        0.0.0.0                  0        100      32768 ?
*>i10.1.1.8/30        10.1.1.5                 0        100          0 ?
*>r10.1.2.0/30        0.0.0.0                  0        100      32768 ?
*>r10.1.2.4/30        0.0.0.0                  0        100      32768 ?
*>r10.1.2.8/30        0.0.0.0                  0        100      32768 ?
*>i10.100.100.0/24    10.1.2.6                          100          0 i
*>r10.150.0.0/30      0.0.0.0                  0        100      32768 ?
*>i172.16.1.0/30      10.1.1.5                 0        100          0 ?
*>i192.168.1.0/30     172.16.1.1               0        100          0 64512 ?
*>i192.168.2.0/30     172.16.1.1               0        100          0 64512 ?
*>i192.168.3.0/30     172.16.1.1               0        100          0 64512 ?
*>i192.168.4.0/30     172.16.1.1               0        100          0 64512 ?
*>i192.168.5.0/30     172.16.1.1               0        100          0 64512 ?

R2#

Nexus R3和Nexus R4接收Nexus R1生成的前缀。

R3# show ip bgp 
BGP routing table information for VRF default, address family IPv4 Unicast
BGP table version is 108, Local Router ID is 10.100.100.1
Status: s-suppressed, x-deleted, S-stale, d-dampened, h-history, *-valid, >-best
Path type: i-internal, e-external, c-confed, l-local, a-aggregate, r-redist, I-injected
Origin codes: i - IGP, e - EGP, ? - incomplete, | - multipath, & - backup, 2 - best2

   Network            Next Hop            Metric     LocPrf     Weight Path
* i10.1.1.4/30        10.1.2.9                 0        100          0 ?
*>i                   10.1.2.5                 0        100          0 ?
*>i10.1.1.8/30        10.1.3.5                 0        100          0 ?
* i                   10.1.2.10                0        100          0 ?
* i10.1.2.0/30        10.1.2.9                 0        100          0 ?
*>i                   10.1.2.5                 0        100          0 ?
* i10.1.2.4/30        10.1.2.9                 0        100          0 ?
*>i                   10.1.2.5                 0        100          0 ?
* i10.1.2.8/30        10.1.3.5                 0        100          0 ?
*>i                   10.1.2.5                 0        100          0 ?
* i10.1.3.0/30        10.1.2.10                0        100          0 ?
*>i                   10.1.3.5                 0        100          0 ?
* i10.1.3.4/30        10.1.2.10                0        100          0 ?
*>i                   10.1.3.5                 0        100          0 ?
*>l10.100.100.0/24    0.0.0.0                           100      32768 i
* i10.150.0.0/30      10.1.2.9                 0        100          0 ?
*>i                   10.1.2.5                 0        100          0 ?
* i10.160.0.0/30      10.1.2.10                0        100          0 ?
*>i                   10.1.3.5                 0        100          0 ?
* i10.200.200.0/24    10.1.3.2                          100          0 i
*>i                   10.1.2.2                          100          0 i
* i172.16.1.0/30      10.1.1.9                 0        100          0 ?
*>i                   10.1.1.5                 0        100          0 ?
* i192.168.1.0/30     172.16.1.1               0        100          0 64512 ?
*>i                   172.16.1.1               0        100          0 64512 ?
* i192.168.2.0/30     172.16.1.1               0        100          0 64512 ?
*>i                   172.16.1.1               0        100          0 64512 ?
* i192.168.3.0/30     172.16.1.1               0        100          0 64512 ?
*>i                   172.16.1.1               0        100          0 64512 ?
* i192.168.4.0/30     172.16.1.1               0        100          0 64512 ?
*>i                   172.16.1.1               0        100          0 64512 ?
* i192.168.5.0/30     172.16.1.1               0        100          0 64512 ?
*>i                   172.16.1.1               0        100          0 64512 ?

R3#

R4# show ip bgp 
BGP routing table information for VRF default, address family IPv4 Unicast
BGP table version is 78, Local Router ID is 10.200.200.1
Status: s-suppressed, x-deleted, S-stale, d-dampened, h-history, *-valid, >-best
Path type: i-internal, e-external, c-confed, l-local, a-aggregate, r-redist, I-injected
Origin codes: i - IGP, e - EGP, ? - incomplete, | - multipath, & - backup, 2 - best2

   Network            Next Hop            Metric     LocPrf     Weight Path
* i10.1.1.4/30        10.1.2.9                 0        100          0 ?
*>i                   10.1.2.1                 0        100          0 ?
*>i10.1.1.8/30        10.1.3.1                 0        100          0 ?
* i                   10.1.2.10                0        100          0 ?
* i10.1.2.0/30        10.1.2.9                 0        100          0 ?
*>i                   10.1.2.1                 0        100          0 ?
* i10.1.2.4/30        10.1.2.9                 0        100          0 ?
*>i                   10.1.2.1                 0        100          0 ?
* i10.1.2.8/30        10.1.3.1                 0        100          0 ?
*>i                   10.1.2.1                 0        100          0 ?
* i10.1.3.0/30        10.1.2.10                0        100          0 ?
*>i                   10.1.3.1                 0        100          0 ?
* i10.1.3.4/30        10.1.2.10                0        100          0 ?
*>i                   10.1.3.1                 0        100          0 ?
* i10.100.100.0/24    10.1.3.6                          100          0 i
*>i                   10.1.2.6                          100          0 i
* i10.150.0.0/30      10.1.2.9                 0        100          0 ?
*>i                   10.1.2.1                 0        100          0 ?
* i10.160.0.0/30      10.1.2.10                0        100          0 ?
*>i                   10.1.3.1                 0        100          0 ?
*>l10.200.200.0/24    0.0.0.0                           100      32768 i
* i172.16.1.0/30      10.1.1.9                 0        100          0 ?
*>i                   10.1.1.5                 0        100          0 ?
* i192.168.1.0/30     172.16.1.1               0        100          0 64512 ?
*>i                   172.16.1.1               0        100          0 64512 ?
* i192.168.2.0/30     172.16.1.1               0        100          0 64512 ?
*>i                   172.16.1.1               0        100          0 64512 ?
* i192.168.3.0/30     172.16.1.1               0        100          0 64512 ?
*>i                   172.16.1.1               0        100          0 64512 ?
* i192.168.4.0/30     172.16.1.1               0        100          0 64512 ?
*>i                   172.16.1.1               0        100          0 64512 ?
* i192.168.5.0/30     172.16.1.1               0        100          0 64512 ?
*>i                   172.16.1.1               0        100          0 64512 ?

R4#

路由反射器获取的前缀显示BGP对等体IP和集群ID。

R4# show ip bgp 192.168.2.0
BGP routing table information for VRF default, address family IPv4 Unicast
BGP routing table entry for 192.168.2.0/30, version 63
Paths: (2 available, best #2)
Flags: (0x8000001a) (high32 00000000) on xmit-list, is in urib, is best urib route, is in HW

  Path type: internal, path is valid, not best reason: Neighbor Address, no labeled nexthop
  AS-Path: 64512 , path sourced external to AS
    172.16.1.1 (metric 0) from 10.1.3.1 (10.160.0.1)      >>>>>>> Peer IP (Cluster ID)
      Origin incomplete, MED 0, localpref 100, weight 0
      Originator: 172.16.1.2 Cluster list: 10.160.0.1 

  Advertised path-id 1
  Path type: internal, path is valid, is best path, no labeled nexthop, in rib
  AS-Path: 64512 , path sourced external to AS
    172.16.1.1 (metric 0) from 10.1.2.1 (10.150.0.1)
      Origin incomplete, MED 0, localpref 100, weight 0
      Originator: 172.16.1.2 Cluster list: 10.150.0.1 

  Path-id 1 not advertised to any peer

R4#

注意：路由反射器接收的Nexus R3和Nexus R4路由不会作为环路避免规则的一部分通告给其他iBGP对等体。

摘要

路由反射器配置不需要复杂的配置来将路由反射到其iBGP客户端，只需在地址系列下添加关键字“route-reflector-client”，即可通知系统充当该邻居的路由反射器。

注意：要查看Nexus中的BGP联盟，请参阅在Nexus 9000上配置BGP联盟

在Nexus 9000上配置BGP路由反射器

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