操縱BGP多出口區分屬性皿￡。)案例MED屬性與本地優先級屬性(localpref)不同，MED在AS間交換，但進入AS的MED不能離開該AS。AS使用Localpref來影響它自已的出站選擇處理。MED是用來影響另一個AS的出站選擇。MED越小，路由優先級越高。R1將1.0.0.0的MED屬性在通告給R3之前設置為50，在通告給R2前設置為100。////r1////intf2/0ipad192.1.1.1255.255.255.0intf3/0ipad193.1.1.1255.255.255.0intlo0ipad1.1.1.1255.255.255.0intlo1ipad2.2.2.2255.255.255.0routerbgp100nosynneighbor192.1.1.2remote-as200

200setmed100outsetmed50outneighbor193.1.1.3remote-as200setmed100outsetmed50outnetwork1.0.0.0network1.0.0.0neighbor192.1.1.2route-mapneighbor193.1.1.3route-mapaccess-list1permit1.0.0.00.255.255.255route-mapsetmed5010matchipad1setmetric50route-mapsetmed5020setmetricroute-mapsetmed10010matchipad1setmetric100route-mapsetmed10020setmetric////r2////intf2/0ipad192.1.1.2255.255.255.0intf4/0ipad194.1.1.2255.255.255.0routeros1netw0.0.0.0255.255.255.255a0passive-interfacef2/0routerbgp200nosynneighbor192.1.1.1remote-as100neighbor194.1.1.4remote-as200neighbor195.1.1.3remote-as200neighbor194.1.1.4next-hop-self////r3////intf3/0ipad193.1.1.3255.255.255.0intf5/0ipad195.1.1.3255.255.255.0routeros1netw0.0.0.0255.255.255.255a0passive-interfacef3/0routerbgp200nosynneighbor193.1.1.1remote-as100neighbor195.1.1.4remote-as200neighbor195.1.1.4next-hop-selfneighbor194.1.1.2remote-as200////r4////intf4/0ipad194.1.1.4255.255.255.0intf5/0ipad195.1.1.4255.255.255.0intlo0ipad4.4.4.4255.255.255.0routeros1netw0.0.0.0255.255.255.255a0routerbgp200nosynneighbor194.1.1.2remote-as200neighbor195.1.1.3remote-as200netw4.0.0.0驗證：r2#shipbgpNetworkNextHopMetricLocPrfWeightPath*>i1.0.0.0193.1.1.1501000100i*192.1.1.11000100i*i2.0.0.0193.1.1.101000100i*>192.1.1.100100i*>i4.0.0.0r2#194.1.1.40 100 0i注意MED值比較低的被選為最佳路徑。r2#shiproB1.0.0.0/8[200/50]via193.1.1.1,00:02:00B2.0.0.0/8[20/0]via192.1.1.1,00:02:004.0.0.0/8isvariablysubnetted,2subnets,2masksO4.4.4.4/32[110/65]via194.1.1.4,00:41:09,Serial4/0B4.0.0.0/8[200/0]via194.1.1.4,00:17:42O193.1.1.0/24[110/192]via194.1.1.4,00:41:09,Serial4/0C192.1.1.0/24isdirectlyconnected,S