1、BGP實驗之操縱BGP路徑選擇 local preference屬性案例(配圖+詳細驗證過程) 作者：JACKSON參考：CISCO中文社區 感謝JACKSON支持原創本地優先級(local pref)屬性是分配給路由的一種優先級度量，用于和到同一目的地的其 他路由相比較。這是BGP路由處理中的第二優先屬性(WEIGHT是第一優先屬性)。Local Pref 屬性只在本AS內部有效，不會被傳送到EBGP鄰居上。本地優先級越高，路由優先級越高。以上案例中，我們通過對R3的配置，設置從R1學到的1.0.0.0的本地優先級(Localpref) 設置為200，由于缺省的值為100，AS200中所有的

2、路由器都會選擇R3到達1.0.0.0。/ r1 /int f2/0ip ad 192.1.1.1 255.255.255.0int f3/0ip ad 193.1.1.1 255.255.255.0 int lo0int lo1ip ad 2.2.2.2 255.255.255.0router bgp 100no synneighbor 192.1.1.2 remote-as 200neighbor 193.1.1.3 remote-as 200network 1.0.0.0network 1.0.0.0/ r2 /int f2/0ip ad 192.1.1.2 255.255.255.0in

3、t f4/0ip ad 194.1.1.2 255.255.255.0router os 1netw 0.0.0.0 255.255.255.255 a 0passive-interface f2/0router bgp 200no synneighbor 192.1.1.1 remote-as 100neighbor 194.1.1.4 remote-as 200neighbor 195.1.1.3 remote-as 200neighbor 194.1.1.4 next-hop-self/ r3 /int f3/0ip ad 193.1.1.3 255.255.255.0int f5/0i

4、p ad 195.1.1.3 255.255.255.0router os 1netw 0.0.0.0 255.255.255.255 a 0passive-interface f3/0router bgp 200no synneighbor 193.1.1.1 remote-as 100neighbor 195.1.1.4 remote-as 200neighbor 195.1.1.4 next-hop-selfneighbor 194.1.1.2 remote-as 200neighbor 193.1.1.1 route-map localpref inaccess-list 1 perm

5、it 1.0.0.0 0.255.255.255route-map localpref permit 10match ip ad 1set local-pref 200route-map localpref permit 20set local-pref 100/ r4 /int f4/0ip ad 194.1.1.4 255.255.255.0int f5/0ip ad 195.1.1.4 255.255.255.0int lo0ip ad 4.4.4.4 255.255.255.0 router os 1router bgp 200no synneighbor 194.1.1.2 remo

6、te-as 200neighbor 195.1.1.3 remote-as 200netw 4.0.0.0驗證：/ r4 /r4#sh ip bgpNetwork Next Hop Metric LocPrf Weight Path*i1.0.0.0 195.1.1.3 0 200 0 100 i* i2.0.0.0 195.1.1.3 0 100 0 100 i*i 194.1.1.2 0 100 0 100 i* 4.0.0.0 0.0.0.0 0 32768 ir4#sh ip roB 1.0.0.0/8 200/0 via 195.1.1.3, 00:02:20B 2.0.0.0/8

7、200/0 via 194.1.1.2, 00:02:244.0.0.0/24 is subnetted, 1 subnetsC 4.4.4.0 is directly connected, Loopback0O 193.1.1.0/24 110/128 via 195.1.1.3, 00:04:35, Serial5/0O 192.1.1.0/24 110/128 via 194.1.1.2, 00:04:35, Serial4/0C 195.1.1.0/24 is directly connected, Serial5/0C 194.1.1.0/24 is directly connect

8、ed, Serial4/0 r2#sh ip bgpNetwork Next Hop Metric LocPrf Weight Path *i1.0.0.0 193.1.1.1 0 200 0 100 i192.1.1.1 0 0 100 ii2.0.0.0 193.1.1.1 0 100 0 100 i* 192.1.1.1 0 0 100 i*i4.0.0.0 194.1.1.4 0 100 0 i r2#sh ip roB 1.0.0.0/8 200/0 via 193.1.1.1, 00:06:00B 2.0.0.0/8 20/0 via 192.1.1.1, 00:06:044.0.0.0/8 is variably subnetted, 2 subnets, 2 masksO 4.4.4.4/32 110/65 via 194.1.1.4, 00:08:20, Serial4/0B 4.0.0.0/8 200/0 via 194.1.1.4, 00:06:55O 193.1.1.0/24 110/192 via 194.1.1.4, 00:08:20, Serial4/0C 192.1.1.0/24