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华为BGP ORF(Outbound Route Filtering)

作者:互联网

RFC5291、RFC5292规定了BGP基于前缀的ORF能力,能将本端设备配置的基于前缀的入口策略通过路由刷新报文发送给BGP邻居。BGP邻居根据这些策略构造出口策略,在路由发送时对路由条目进行过滤。这样不仅避免了本端设备接收大量无用的路由,降低了本端设备的CPU使用率,还有效减少了BGP邻居的配置工作,降低了链路带宽的占用率。

 image.png

 

配置基于前缀的BGP ORF示例

组网需求:

如图所示,AR1属于AS100,AR3属于AS200。需求AR3不必维护出口策略即可实现AR3设备只发送符合AR1设备入口策略的路由。

image.png

一、完成接口及EBGP配置。(略)

二、在AR3上应用基于前缀的入口过滤

R3:

ip ip-prefix 10 index 10 permit 100.1.1.0 24

 

bgp 200

   peer 123.1.1.1 ip-prefix 10 import

 

在AR3上查看路由表:

[AR3]dis bgp routing-table

 

 BGP Local router ID is 33.1.1.1

 Status codes: * - valid, > - best, d - damped,

               h - history,  i - internal, s - suppressed, S - Stale

               Origin : i - IGP, e - EGP, ? - incomplete

 

 

 Total Number of Routes: 4

      Network            NextHop        MED        LocPrf    PrefVal Path/Ogn

*>   100.1.1.0/24          123.1.1.1       0                     0      100i

 

在AR3上查看路由接收情况:

[AR3]dis bgp routing-table peer 123.1.1.1 received-routes

 

 BGP Local router ID is 33.1.1.1

 Status codes: * - valid, > - best, d - damped,

               h - history,  i - internal, s - suppressed, S - Stale

               Origin : i - IGP, e - EGP, ? - incomplete

 

 

 Total Number of Routes: 1

      Network            NextHop        MED        LocPrf    PrefVal Path/Ogn

 

 *>   100.1.1.0/24       123.1.1.1       0                     0      100i

 在AR1上查看路由发送情况:

[AR1]dis bgp routing-table peer 123.1.1.3 advertised-routes

 

 BGP Local router ID is 123.1.1.1

 Status codes: * - valid, > - best, d - damped,

               h - history,  i - internal, s - suppressed, S - Stale

               Origin : i - IGP, e - EGP, ? - incomplete

 

 

 Total Number of Routes: 4

      Network            NextHop        MED        LocPrf    PrefVal Path/Ogn

 

*>   11.1.1.0/24         123.1.1.1       0                     0       100i

 *>   100.1.1.0/24       123.1.1.1       0                     0      100i

 *>   111.1.1.0/24       123.1.1.1       0                      0      100 i

未使能基于前缀的BGP ORF功能时,AR1发送了11.1.1.0、100.1.1.0、111.1.0三条直连环回口路由,AR3的基于前缀列表的入口策略只接收了100.1.1.0的路由。

 

三、使能基于前缀的BGP ORF功能

# 在AR1上使能基于前缀的BGP ORF功能。

[AR1] bgp 100

[AR1-bgp] peer 123.1.1.3 capability-advertise orf ip-prefix both

[AR1-bgp] quit

# 在AR3上使能基于前缀的BGP ORF功能。

[AR3] bgp 200

[AR3-bgp] peer 123.1.1.1 capability-advertise orf ip-prefix both

[AR3-bgp] quit

注意:配置完成以后,会导致邻居shutdown掉,重新建立BGP邻居关系。

此时查看AR1通告的路由,AR1只通告100.1.1.0/24的路由,不会通告其他的路由条目,可以减少路由条目的发送。

[AR1]dis bgp routing-table peer 123.1.1.3 advertised-routes //查看BGP通告的路由条目

 

 BGP Local router ID is 123.1.1.1

 Status codes: * - valid, > - best, d - damped,

               h - history,  i - internal, s - suppressed, S - Stale

               Origin : i - IGP, e - EGP, ? - incomplete

 

 

 Total Number of Routes: 4

      Network            NextHop        MED        LocPrf    PrefVal Path/Ogn

*>   100.1.1.0/24          123.1.1.1       0                     0      100i

 

<AR1>dis bgp peer 123.1.1.3 verbose   //查看基于前缀的BGP ORF协商信息。

 

        BGP Peer is 123.1.1.3,  remote AS 200 

        Type: EBGP link

        BGP version 4, Remote router ID 33.1.1.1

        Update-group ID: 0 

        BGP current state: Established, Up for 00h13m07s

        BGP current event: RecvKeepalive

        BGP last state: OpenConfirm

        BGP Peer Up count: 2

        Received total routes: 1

        Received active routes total: 1

        Advertised total routes: 4

        Port:  Local - 179      Remote - 51051

        Configured: Connect-retry Time: 32 sec

        Configured: Active Hold Time: 180 sec   Keepalive Time:60 sec

        Received  : Active Hold Time: 180 sec

        Negotiated: Active Hold Time: 180 sec   Keepalive Time:60 sec

        Peer optional capabilities:

        Peer supports bgp multi-protocol extension

        Peer supports bgp route refresh capability

        Peer supports bgp outbound route filter capability

        Support Address-Prefix: IPv4-UNC address-family, rfc-compatible, both

        Peer supports bgp 4-byte-as capability

        Address family IPv4 Unicast: advertised and received

 

wireshark抓包显示如下:

image.png

 


标签:bgp,Filtering,Outbound,1.1,Route,123.1,BGP,AR3,路由
来源: https://blog.51cto.com/3965485/2444174