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示例:使用 AS 路径正则表达式

date_range 18-Jan-25

自治系统 (AS) 路径是 BGP 使用的路由属性。AS 路径既用于路由选择,也用于防止潜在的路由环路。此示例说明如何使用带有 AS 路径号的正则表达式来定位一组路由。

要求

配置此示例之前,不需要除设备初始化之外的特殊配置。

概述

图 1 显示了通过外部 BGP (EBGP) 对等会话连接的多个 AS。每个设备都在其分配的地址空间内生成客户路由。

拓扑学

图 1 显示了示例网络。

图 1: BGP 拓扑 AS 正则表达式BGP 拓扑 AS 正则表达式

AS 64516 的管理员希望拒绝源自 AS 64513 和 AS 64514 的所有路由。在名为 reject-some-routes的策略中创建并引用了两个 AS 路径正则表达式。orig-in-64513orig-in-64514 然后,路由策略将作为导入策略应用到设备 R6 上。

CLI 快速配置 显示了 中 图 1所有设备的配置。

#configuration488__policy-as-path-regex-st本节介绍设备 R2 和设备 R6 上的步骤。验证展示了如何将选项与设备 R2 上的命令一起使用aspath-regexshow route,以使用正则表达式查找路由。

配置

CLI 快速配置

要快速配置此示例,请复制以下命令,将其粘贴到文本文件中,删除所有换行符,更改与您的网络配置匹配所需的任何详细信息,然后将命令复制并粘贴到层次结构级别的 CLI [edit] 中。

设备 R1

content_copy zoom_out_map
set interfaces fe-1/2/2 unit 0 description to-R2
set interfaces fe-1/2/2 unit 0 family inet address 10.2.0.2/30
set interfaces fe-1/2/3 unit 0 description to-R3
set interfaces fe-1/2/3 unit 0 family inet address 10.2.0.6/30
set interfaces fe-1/2/0 unit 0 description to-R5
set interfaces fe-1/2/0 unit 0 family inet address 10.0.0.2/30
set interfaces lo0 unit 0 family inet address 192.168.0.1/32
set protocols bgp export send-static
set protocols bgp group 64512 type external
set protocols bgp group 64512 peer-as 64512
set protocols bgp group 64512 neighbor 10.2.0.1
set protocols bgp group 64513 type external
set protocols bgp group 64513 peer-as 64513
set protocols bgp group 64513 neighbor 10.2.0.5
set protocols bgp group 64515 type external
set protocols bgp group 64515 peer-as 64515
set protocols bgp group 64515 neighbor 10.0.0.1
set policy-options policy-statement send-static term 1 from protocol static
set policy-options policy-statement send-static term 1 then accept
set routing-options static route 10.10.1.0/24 reject
set routing-options static route 10.10.2.0/24 reject
set routing-options static route 10.10.3.0/24 reject
set routing-options autonomous-system 64511

设备 R2

content_copy zoom_out_map
set interfaces fe-1/2/2 unit 0 description to-R1
set interfaces fe-1/2/2 unit 0 family inet address 10.2.0.1/30
set interfaces lo0 unit 0 family inet address 192.168.0.2/32
set protocols bgp export send-static
set protocols bgp group 64511 type external
set protocols bgp group 64511 peer-as 64511
set protocols bgp group 64511 neighbor 10.2.0.2
set policy-options policy-statement send-static term 1 from protocol static
set policy-options policy-statement send-static term 1 then accept
set routing-options static route 10.20.1.0/24 reject
set routing-options static route 10.20.2.0/24 reject
set routing-options static route 10.20.3.0/24 reject
set routing-options autonomous-system 64512

设备 R3

content_copy zoom_out_map
set interfaces fe-1/2/3 unit 0 description to-R1
set interfaces fe-1/2/3 unit 0 family inet address 10.2.0.5/30
set interfaces fe-1/2/2 unit 0 description to-R4
set interfaces fe-1/2/2 unit 0 family inet address 10.3.0.42/30
set interfaces lo0 unit 0 family inet address 192.168.0.3/32
set protocols bgp export send-static
set protocols bgp group 64511 type external
set protocols bgp group 64511 peer-as 64511
set protocols bgp group 64511 neighbor 10.2.0.6
set protocols bgp group 64514 type external
set protocols bgp group 64514 peer-as 64514
set protocols bgp group 64514 neighbor 10.3.0.41
set policy-options policy-statement send-static term 1 from protocol static
set policy-options policy-statement send-static term 1 then accept
set routing-options static route 10.30.1.0/24 reject
set routing-options static route 10.30.2.0/24 reject
set routing-options static route 10.30.3.0/24 reject
set routing-options autonomous-system 64513

设备 R4

content_copy zoom_out_map
set interfaces fe-1/2/2 unit 0 description to-R3
set interfaces fe-1/2/2 unit 0 family inet address 10.3.0.41/30
set interfaces lo0 unit 0 family inet address 192.168.0.4/32
set protocols bgp export send-static
set protocols bgp group 64513 type external
set protocols bgp group 64513 peer-as 64513
set protocols bgp group 64513 neighbor 10.3.0.42
set policy-options policy-statement send-static term 1 from protocol static
set policy-options policy-statement send-static term 1 then accept
set routing-options static route 10.40.1.0/24 reject
set routing-options static route 10.40.2.0/24 reject
set routing-options static route 10.40.3.0/24 reject
set routing-options autonomous-system 64514

设备 R5

content_copy zoom_out_map
set interfaces fe-1/2/0 unit 0 description to-R1
set interfaces fe-1/2/0 unit 0 family inet address 10.0.0.1/30
set interfaces fe-1/2/1 unit 0 description to-R6
set interfaces fe-1/2/1 unit 0 family inet address 10.0.0.9/30
set interfaces lo0 unit 0 family inet address 192.168.0.5/32
set protocols bgp export send-static
set protocols bgp group 64511 type external
set protocols bgp group 64511 peer-as 64511
set protocols bgp group 64511 neighbor 10.0.0.2
set protocols bgp group 64516 type external
set protocols bgp group 64516 peer-as 64516
set protocols bgp group 64516 neighbor 10.0.0.10
set policy-options policy-statement send-static term 1 from protocol static
set policy-options policy-statement send-static term 1 then accept
set routing-options static route 10.50.1.0/24 reject
set routing-options static route 10.50.2.0/24 reject
set routing-options static route 10.50.3.0/24 reject
set routing-options autonomous-system 64515

设备 R6

content_copy zoom_out_map
set interfaces fe-1/2/1 unit 0 description to-R5
set interfaces fe-1/2/1 unit 0 family inet address 10.0.0.10/30
set interfaces lo0 unit 0 family inet address 192.168.0.6/32
set protocols bgp export send-static
set protocols bgp group 64515 type external
set protocols bgp group 64515 import reject-some-routes
set protocols bgp group 64515 peer-as 64515
set protocols bgp group 64515 neighbor 10.0.0.9
set policy-options policy-statement send-static term 1 from protocol static
set policy-options policy-statement send-static term 1 then accept
set policy-options policy-statement reject-some-routes term find-routes from as-path orig-in-64513
set policy-options policy-statement reject-some-routes term find-routes from as-path orig-in-64514
set policy-options policy-statement reject-some-routes term find-routes then reject
set policy-options as-path orig-in-64513 ".* 64513"
set policy-options as-path orig-in-64514 ".* 64514"
set routing-options static route 10.60.1.0/24 reject
set routing-options static route 10.60.2.0/24 reject
set routing-options static route 10.60.3.0/24 reject
set routing-options autonomous-system 64516

程序

分步过程

以下示例要求您在配置层次结构中导航各个级别。有关导航 CLI 的信息,请参阅 在配置模式下使用 CLI 编辑器Junos OS CLI 用户指南

要配置设备 R2:

  1. 配置设备接口。

    content_copy zoom_out_map
    [edit interfaces]
    user@R2# set fe-1/2/2 unit 0 description to-R1
    user@R2# set fe-1/2/2 unit 0 family inet address 10.2.0.1/30
    user@R2# set lo0 unit 0 family inet address 192.168.0.2/32
    
  2. 配置与设备 R1 的 EBGP 连接。

    content_copy zoom_out_map
    [edit protocols bgp]
    user@R2# set export send-static
    user@R2# set group 64511 type external
    user@R2# set group 64511 peer-as 64511
    user@R2# set group 64511 neighbor 10.2.0.2
    
  3. 配置路由策略。

    content_copy zoom_out_map
    [edit policy-options policy-statement send-static term 1]
    user@R2# set from protocol static
    user@R2# set then accept
    
  4. 配置静态路由。

    content_copy zoom_out_map
    [edit routing-options static]
    user@R2# set route 10.20.1.0/24 reject
    user@R2# set route 10.20.2.0/24 reject
    user@R2# set route 10.20.3.0/24 reject
    
  5. 配置 AS 编号。

    content_copy zoom_out_map
    [edit routing-options]
    user@R2# set autonomous-system 64512
    

分步过程

以下示例要求您在配置层次结构中导航各个级别。有关导航 CLI 的信息,请参阅 在配置模式下使用 CLI 编辑器Junos OS CLI 用户指南

要配置设备 R6:

  1. 配置设备接口。

    content_copy zoom_out_map
    [edit interfaces]
    user@R6# set fe-1/2/1 unit 0 description to-R5
    user@R6# set fe-1/2/1 unit 0 family inet address 10.0.0.10/30
    user@R6# set lo0 unit 0 family inet address 192.168.0.6/32
    
  2. 配置与设备 R5 的 EBGP 连接。

    content_copy zoom_out_map
    [edit protocols bgp]
    user@R6# set export send-static
    user@R6# set group 64515 type external
    user@R6# set group 64515 import reject-some-routes
    user@R6# set group 64515 peer-as 64515
    user@R6# set group 64515 neighbor 10.0.0.9
    
  3. 配置发送静态路由的路由策略。

    content_copy zoom_out_map
    [edit policy-options policy-statement send-static term 1]
    user@R6# set  from protocol static
    user@R6# set then accept
    
  4. 配置拒绝某些路由的路由策略。

    content_copy zoom_out_map
    [edit policy-options policy-statement reject-some-routes term find-routes]
    user@R6# set from as-path orig-in-64513
    user@R6# set from as-path orig-in-64514
    user@R6# set then reject
    [edit policy-options]
    user@R6# set as-path orig-in-64513 ".* 64513"
    user@R6# set as-path orig-in-64514 ".* 64514"
    
  5. 配置静态路由。

    content_copy zoom_out_map
    [edit routing-options static]
    user@R6# set route 10.60.1.0/24 reject
    user@R6# set route 10.60.2.0/24 reject
    user@R6# set route 10.60.3.0/24 reject
    
  6. 配置 AS 编号。

    content_copy zoom_out_map
    [edit routing-options]
    user@R6# set autonomous-system 64516
    

结果

在配置模式下,输入 show interfacesshow protocolsshow policy-optionsshow routing-options 命令,以确认您的配置。如果输出未显示预期的配置,请重复此示例中的说明,以便进行更正。

设备 R2

content_copy zoom_out_map
user@R2# show interfaces
fe-1/2/0 {
    unit 0 {
        description to-R1;
        family inet {
            address 10.2.0.1/30;
        }
    }
}
lo0 {
    unit 0 {
        family inet {
            address 192.168.0.2/32;
        }
    }
}
content_copy zoom_out_map
user@R2# show protocols
bgp {
    export send-static;
    group 64511 {
        type external;
        peer-as 64511;
        neighbor 10.2.0.2;
    }
}
content_copy zoom_out_map
user@R2# show policy-options
policy-statement send-static {
    term 1 {
        from protocol static;
        then accept;
    }
}
content_copy zoom_out_map
user@R2# show routing-options
static {
    route 10.20.1.0/24 reject;
    route 10.20.2.0/24 reject;
    route 10.20.3.0/24 reject;
}
autonomous-system 64512;

设备 R6

content_copy zoom_out_map
user@R6# show interfaces
fe-1/2/0 {
    unit 0 {
        description to-R5;
        family inet {
            address 10.0.0.10/30;
        }
    }
}
lo0 {
    unit 0 {
        family inet {
            address 192.168.0.6/32;
        }
    }
}
content_copy zoom_out_map
user@R6# show protocols
bgp {
    export send-static;
    group 64515 {
        type external;
        import reject-some-routes;
        peer-as 64515;
        neighbor 10.0.0.9;
    }
}
content_copy zoom_out_map
user@R6# show policy-options
policy-statement reject-some-routes {
    term find-routes {
        from as-path [ orig-in-64513 orig-in-64514 ];
        then reject;
    }
}
policy-statement send-static {
    term 1 {
        from protocol static;
        then accept;
    }
}
as-path orig-in-64513 ".* 64513";
as-path orig-in-64514 ".* 64514";
content_copy zoom_out_map
user@R6# show routing-options
static {
    route 10.60.1.0/24 reject;
    route 10.60.2.0/24 reject;
    route 10.60.3.0/24 reject;
}
autonomous-system 64516;

如果完成设备配置,请从配置模式输入 commit

验证

确认配置工作正常。

在设备 R2 上查找路由

目的

在设备 R2 上,使用命令通过 show route aspath-regex 正则表达式定位路由。

操作

在 AS 64516 中查找由设备 R6 发起的路由。

content_copy zoom_out_map
user@R2> show route terse aspath-regex ".* 64516"

inet.0: 21 destinations, 21 routes (21 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

A V Destination        P Prf   Metric 1   Metric 2  Next hop        AS path
* ? 10.60.1.0/24       B 170        100                             64511 64515 64516 I
  unverified                                       >10.2.0.2
* ? 10.60.2.0/24       B 170        100                             64511 64515 64516 I
  unverified                                       >10.2.0.2
* ? 10.60.3.0/24       B 170        100                             64511 64515 64516 I
  unverified                                       >10.2.0.2

查找源自 AS 64514 或 AS 64516 的路由。

content_copy zoom_out_map
user@R2> show route terse aspath-regex ".* (64514|64516)"

inet.0: 21 destinations, 21 routes (21 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

A V Destination        P Prf   Metric 1   Metric 2  Next hop        AS path
* ? 10.40.1.0/24       B 170        100                             64511 64513 64514 I
  unverified                                       >10.2.0.2
* ? 10.40.2.0/24       B 170        100                             64511 64513 64514 I
  unverified                                       >10.2.0.2
* ? 10.40.3.0/24       B 170        100                             64511 64513 64514 I
  unverified                                       >10.2.0.2
* ? 10.60.1.0/24       B 170        100                             64511 64515 64516 I
  unverified                                       >10.2.0.2
* ? 10.60.2.0/24       B 170        100                             64511 64515 64516 I
  unverified                                       >10.2.0.2
* ? 10.60.3.0/24       B 170        100                             64511 64515 64516 I
  unverified                                       >10.2.0.2

查找使用 AS 64513 作为中转网络的路由。

content_copy zoom_out_map
user@R2> show route terse aspath-regex ".* 64513 .+"

inet.0: 21 destinations, 21 routes (21 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

A V Destination        P Prf   Metric 1   Metric 2  Next hop        AS path
* ? 10.40.1.0/24       B 170        100                             64511 64513 64514 I
  unverified                                       >10.2.0.2
* ? 10.40.2.0/24       B 170        100                             64511 64513 64514 I
  unverified                                       >10.2.0.2
* ? 10.40.3.0/24       B 170        100                             64511 64513 64514 I
  unverified                          

意义

输出显示与指定的 AS 路径正则表达式匹配的路由表条目。

确保在设备 R6 上排除路由

目的

在设备 R6 上,使用命令确保 show route and show route hidden 从设备 R6 的路由表中排除源自 AS 64513 和 AS 64514 的路由。

操作

content_copy zoom_out_map
user@R6> show route 10.30.0/22
inet.0: 21 destinations, 21 routes (15 active, 0 holddown, 6 hidden)
content_copy zoom_out_map
user@R6> show route 10.40.0/22
inet.0: 21 destinations, 21 routes (15 active, 0 holddown, 6 hidden)
content_copy zoom_out_map
user@R6> show route hidden

inet.0: 21 destinations, 21 routes (15 active, 0 holddown, 6 hidden)
+ = Active Route, - = Last Active, * = Both

10.30.1.0/24        [BGP ] 02:24:47, localpref 100
                      AS path: 64515 64511 64513 I, validation-state: unverified
                    > to 10.0.0.9 via fe-1/2/1.0
10.30.2.0/24        [BGP ] 02:24:47, localpref 100
                      AS path: 64515 64511 64513 I, validation-state: unverified
                    > to 10.0.0.9 via fe-1/2/1.0
10.30.3.0/24        [BGP ] 02:24:47, localpref 100
                      AS path: 64515 64511 64513 I, validation-state: unverified
                    > to 10.0.0.9 via fe-1/2/1.0
10.40.1.0/24        [BGP ] 02:24:47, localpref 100
                      AS path: 64515 64511 64513 64514 I, validation-state: unverified
                    > to 10.0.0.9 via fe-1/2/1.0
10.40.2.0/24        [BGP ] 02:24:47, localpref 100
                      AS path: 64515 64511 64513 64514 I, validation-state: unverified
                    > to 10.0.0.9 via fe-1/2/1.0
10.40.3.0/24        [BGP ] 02:24:47, localpref 100
                      AS path: 64515 64511 64513 64514 I, validation-state: unverified
                    > to 10.0.0.9 via fe-1/2/1.0

意义

输出显示设备 R6 上的 10.30.0/22 和 10.40.0/22 路由被拒绝。

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