CCIE实验备考之BGP（3）

汇总设置：
     1.bgp是无类路由协议，支持VLSM，但会要求最长匹配，一般它默认启动自动汇总的，但我们要求关闭自动汇总，不然就会像EIGRP那样出现问题，命令：
              no auto-summary
     2.手工汇总方法1：
            1）  network 汇总路由 mask 汇总后的子网掩码
            2）  ip route 汇总路由 汇总后的子网掩码 null0
        network命令本身不能汇总路由，它只是把经过igp汇总后的路由发布出去，然后还要手工指定一条静态汇总路由，指向null接口，不仅发布汇总路由，也会把具体的路由发布出去，如果不想把具体路由发布出去，需要路由过滤。
     3.手工汇总方法2：
            aggregate-address ip地址 子网掩码 参数
            参数：
 summary-only：只发送汇总的路由，具体的路由不会发布出去
r2#show ip route
Codes: 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, 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

Gateway of last resort is not set

B    199.1.3.0/24 [20/0] via 192.1.1.1, 00:00:09     //要汇总的条目
B    199.1.2.0/24 [20/0] via 192.1.1.1, 00:00:09
B    199.1.1.0/24 [20/0] via 192.1.1.1, 00:00:09
C    193.1.1.0/24 is directly connected, Ethernet0
C    192.1.1.0/24 is directly connected, Serial1
B    199.1.4.0/24 [20/0] via 192.1.1.1, 00:00:09
B    199.1.0.0/22 [20/0] via 192.1.1.1, 00:00:09   //这是汇总之后的路由
加入参数后
r2#show ip route
Codes: 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, 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

Gateway of last resort is not set

C    193.1.1.0/24 is directly connected, Ethernet0
C    192.1.1.0/24 is directly connected, Serial1
B    199.1.0.0/22 [20/0] via 192.1.1.1, 00:00:09

r1#show ip bgp
BGP table version is 18, local router ID is 192.168.194.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 192.1.1.0        0.0.0.0                  0         32768 ?
*> 193.1.1.0        0.0.0.0                  2         32768 ?
s> 199.1.2.0        0.0.0.0                  0         32768 ?    //抑制住的路由
*> 192.168.192.0/21 0.0.0.0                            32768 i
s> 199.1.1.0        0.0.0.0                  0         32768 ?
s> 199.1.3.0        0.0.0.0                  0         32768 ?
s> 199.1.4.0        0.0.0.0                  2         32768 ?
   
 as-set:用于汇总路由指明具体路由所经过的 AS（的集合），以避免产生环路
r4#show ip bgp 
BGP table version is 29, local router ID is 200.200.200.201
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*>i192.168.192.0/21 10.1.1.9                      100      0 i
*> 200.200.200.0    0.0.0.0                  0         32768 i
设置参数后：
r4#show ip bgp
BGP table version is 30, local router ID is 200.200.200.201
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*>i192.168.192.0/21 10.1.1.9                      100      0 {50,200} i
*> 200.200.200.0    0.0.0.0                  0         32768 i
   
 attribute-map:用于汇总路由的属性指定
router bgp 100
 aggregate-address 192.168.192.0 255.255.248.0 as-set summary-only attribute-map cisco1
!
route-map cisco1 permit 10
 set local-preference 200
 set origin incomplete
!
r4#show ip bgp
BGP table version is 46, local router ID is 200.200.200.201
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*>i192.168.192.0/21 10.1.1.9                      200      0 {50,200} ?
*> 200.200.200.0    0.0.0.0                  0         32768 i    

 advertise-map:在公布带有 as-set的聚合路由时，不希望该聚合路由继承所有被聚合路由的所有属性
r4#show ip bgp
BGP table version is 17, local router ID is 200.200.200.201
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*>i192.168.192.0/21 10.1.1.9                      100      0 {50,200} i
*> 200.200.200.0    0.0.0.0                  0         32768 i
修改加参数：
router bgp 100
 aggregate-address 192.168.192.0 255.255.248.0 as-set summary-only advertise-map cisco
 ......
!
ip as-path access-list 1 permit ^200$
!
route-map cisco permit 10
 match as-path 1
!

r4#show ip bgp
BGP table version is 17, local router ID is 200.200.200.201
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*>i192.168.192.0/21 10.1.1.9                      100      0 200 i
*> 200.200.200.0    0.0.0.0                  0         32768 i

 

 

   access-list 1 deny   192.168.196.0
  access-list 1 permit any

2.prefix-list前缀列表过滤
  命令：
      ip prefix-list 列表号 [seq 序号] {deny | permit} 网络号/len匹配长度 [ge 最小匹配值] [le 最大匹配值]
      其中：
          len < ge <= le
          如果存在ge和le，则len匹配长度将会被忽略
  应用：
      neighbor 邻居 prefix-list 名称 [in | out]
  注意：prefix-list和distribute-list不能同时应用在同一个邻居上，但distribute-list可以调用prefix-list定义的列表
  例如：
      router bgp 100
        aggregate-address 192.168.192.0 255.255.248.0 suppress-map supmap
        neighbor 10.1.1.1 remote-as 50
        neighbor 10.1.1.5 remote-as 200
        neighbor 10.1.1.10 remote-as 100
        neighbor 10.1.1.10 next-hop-self
        neighbor 10.1.1.10 send-community
        neighbor 10.1.1.10 prefix-list cisco out
        ......
      !
      ip prefix-list cisco seq 5 permit 192.168.192.0/21 ge 22 le 24

      r3#show ip bgp
      BGP table version is 17, local router ID is 3.3.3.3
      Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
      Origin codes: i - IGP, e - EGP, ? - incomplete

      Network          Next Hop            Metric LocPrf Weight Path
      s> 192.168.192.0    10.1.1.1                 0             0 50 i
      *> 192.168.192.0/21 0.0.0.0                            32768 i
      *> 192.168.193.0    10.1.1.1                 0             0 50 i
      *> 192.168.194.0    10.1.1.1                 0             0 50 i
      *> 192.168.196.0    10.1.1.5                 0             0 200 i
      s> 192.168.197.0    10.1.1.5                 0             0 200 i
      *> 192.168.198.0    10.1.1.5                 0             0 200 i
      *>i200.200.200.0    10.1.1.10                0    100      0 i

3.AS-PATH过滤
 命令：
     ip as-path access-list 编号 { permit | deny } 正则表达式
     其中表达式的原则：
        .                        任何单一字符，包括空格
       []                        在方括号中罗列的任何字符
       [^]                       除了在方括号中所罗列字符外的任何字符（^必须放在字符列表之前）
       -                        （连字符）在由连字符所分配的两个字符之间的任意字符
       ？                        字符或模式出现 0次或 1次
       *                         字符或模式出现 0次或多次
       +                         字符或模式出现 1次或多次
       ^                         一行的开始
       $                         一行的结束
       |                         由元字符特殊字符分隔的字之一
       _                        （下划线）一个逗号，行的开始，行的结束或空格
  例如：
     ip as-path access-list 1 permit ^(850|860)*$
     将在AS-PATH中匹配重复多次的AS号为850或860列表，如（850），（850，850，850），（850，850，888）或（860），（860，860，860）等
  应用：
     neighbor 邻居 filter-list as-path定义的编号 [ in | out ]
  案例：
     r4#show ip bgp
     BGP table version is 16, local router ID is 200.200.200.201
     Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
     Origin codes: i - IGP, e - EGP, ? - incomplete

        Network          Next Hop            Metric LocPrf Weight Path
     *>i192.168.193.0    10.1.1.9                 0    100      0 50 i
     *>i192.168.194.0    10.1.1.9                 0    100      0 50 i
     *>i192.168.196.0    10.1.1.9                 0    100      0 200 i
     *>i192.168.198.0    10.1.1.9                 0    100      0 200 i
     *> 200.200.200.0    0.0.0.0                  0         32768 i
    

      ip as-path access-list 1 permit ^50$
  access-list 1 permit 192.168.193.0
  access-list 1 permit 192.168.195.0
  route-map mapcisco permit 10
    match ip address 1

 r4#show ip bgp
BGP table version is 22, local router ID is 200.200.200.201
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*>i192.168.193.0    10.1.1.9                 0    100      0 50 i
*>i192.168.194.0    10.1.1.9                 0    100      0 50 i
*> 200.200.200.0    0.0.0.0                  0         32768 i
----------------------------------------------------------------------------------

本文出自 “无聊生活，积极面对” 博客，谢绝转载！