【正文】 paths, scan interval 60 secsNeighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 4 2 5 6 2 0 0 00:01:01 0 網(wǎng)絡(luò)通告要通過(guò)BGP協(xié)議通告目標(biāo)網(wǎng)絡(luò)，必須首先把路由條目注入進(jìn)BGP中。總共有三種方法：（1） 通過(guò)把從IGP學(xué)習(xí)到的路由條目重分發(fā)進(jìn)BGP中； ？（2） 通過(guò)network命令把網(wǎng)絡(luò)宣告進(jìn)BGP中； i（3） 通過(guò)添加靜態(tài)路由條目，然后再使用network命令把網(wǎng)絡(luò)宣告進(jìn)BGP中； iR2show ip bgp查看當(dāng)前路由器的BGP 轉(zhuǎn)發(fā)表BGP table version is 2, local router ID is Status codes: s suppressed, d damped, h history, * valid, best, i internal, r RIBfailure, S StaleOrigin codes: i IGP, e EGP, ? inplete Network Next Hop Metric LocPrf Weight Path* 要給BGP對(duì)端通告一條默認(rèn)路由，總共有三種方法可以實(shí)現(xiàn)。ip route null 0redistribute staticdefaultinformation originate*Jul 7 12:53:: BGP: Applying map to find origin for R1sh ip bgp BGP table version is 3, local router ID is Status codes: s suppressed, d damped, h history, * valid, best, i internal, r RIBfailure, S StaleOrigin codes: i IGP, e EGP, ? inplete Network Next Hop Metric LocPrf Weight Path* 0 32768 ?* R3sh ip bgp BGP table version is 4, local router ID is Status codes: s suppressed, d damped, h history, * valid, best, i internal, r RIBfailure, S StaleOrigin codes: i IGP, e EGP, ? inplete Network Next Hop Metric LocPrf Weight Path* 0 0 1 ?（3） 在IGP表中首先建立指向NULL 0的路由條目，然后使用network命令通告出去。此時(shí)觀察R2 BGP轉(zhuǎn)發(fā)表R2sh ip bgp BGP table version is 6, local router ID is Status codes: s suppressed, d damped, h history, * valid, best, i internal, r RIBfailure, S StaleOrigin codes: i IGP, e EGP, ? inplete Network Next Hop Metric LocPrf Weight Path* 0 2 1 i這里由于R1 和R2 是EBGP對(duì)等體關(guān)系，所以R1 從R3 R4 網(wǎng)絡(luò)在通告給R2 時(shí)將自己的ROUTERID作為下一條IP 給R2這里我們發(fā)現(xiàn)R2 R2sh ip routeCodes: 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 ISIS, su ISIS summary, L1 ISIS level1, L2 ISIS level2 ia ISIS inter area, * candidate default, U peruser static route o ODR, P periodic downloaded static routeGateway of last resort is not set , 1 subnetsO [110/65] via , 00:01:54, Serial1/0 , 1 subnetsC is directly connected, Loopback0 , 1 subnetsO [110/65] via , 00:01:54, Serial1/1 , 1 subnetsO [110/129] via , 00:01:54, Serial1/1 , 3 subnetsO [110/128] via , 00:01:54, Serial1/1C is directly connected, Serial1/1C is directly connected, Serial1/0B [20/0] via , 00:01:45這里我們使用traceroute ip命令發(fā)現(xiàn)R2 。9:理解BGP 自動(dòng)匯總BGP的自動(dòng)匯總是關(guān)閉的當(dāng)自動(dòng)匯總開(kāi)啟時(shí),如果你使用NETWORK 語(yǔ)句進(jìn)行網(wǎng)絡(luò)通告時(shí),如果你宣告的是主網(wǎng)地址,那么BGP會(huì)查看本地的路由表查看是否有該主網(wǎng)的子網(wǎng),如果有說(shuō)明是有明細(xì)子網(wǎng)的主網(wǎng)信息,就可以直接將主網(wǎng)宣告出去,. BGP基本的匯總概念R1!interface Loopback0 ip address !interface Loopback1 ip address !interface Loopback2 ip address !router bgp 1 no synchronization bgp logneighborchanges neighbor remoteas 1 no autosummary!!interface Serial1/1 ip address no sh!EndR2!router bgp 1 no synchronization bgp logneighborchanges neighbor remoteas 1 no autosummary!interface Serial1/0 ip address no sh!R1sh ip protocols Routing Protocol is bgp 1 Outgoing update filter list for all interfaces is not set Ining update filter list for all interfaces is not set IGP synchronization is disabled Automatic route summarization is disabled Neighbor(s): Address FiltIn FiltOut DistIn DistOut Weight RouteMap Maximum path: 1 Routing Information Sources: Gateway Distance Last Update Distance: external 20 internal 200 local 200默認(rèn)時(shí)只要你使用了NET命令都必須匹配網(wǎng)絡(luò)掩碼,可以進(jìn)行匯總的宣告及不一定非要匹配路由表?xiàng)l目.NETWORK 我們發(fā)現(xiàn)R1 R2 轉(zhuǎn)發(fā)表都為空R1SHOW IP BGP因?yàn)樵摼W(wǎng)絡(luò)不在路由表內(nèi)如果想宣告你可以做一個(gè)NULL0路由R1(config)ip route null 0R1(config)endR1sh ip routeCodes: 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 ISIS, su ISIS summary, L1 ISIS level1, L2 ISIS level2 ia ISIS inter area, * candidate default, U peruser static route o ODR, P periodic downloaded static routeGateway of last resort is not set , 4 subnets, 2 masksS , Null0C , Loopback0C , Loopback1C , Loopback2 , 1 subnetsC is directly connected, Serial1/1R1R1R1sh *May 9 16:54:: %SYS5CONFIG_I: Configured from console by consoleR1sh ip bgp BGP table version is 2, local router ID is Status codes: s suppressed, d damped, h history, * valid, best, i internal, r RIBfailure, S StaleOrigin codes: i IGP, e EGP, ? inplete Network Next Hop Metric LocPrf Weight Path* 0 32768 i但如果不加該默認(rèn)路由可以打開(kāi)自動(dòng)匯總，那么只要不匹配路由表他會(huì)以匯總路由方式發(fā)送 重分發(fā)時(shí)的自動(dòng)匯總R3 EnableConf tHost R1No ip do lo Line cons 0Logg syncNo exect!!!interface Loopback0 ip address !interface FastEthernet0/0 ip address duplex half!router rip version 2 network network no autosummary!R1!interface FastEthernet0/0 ip address !interface Serial1/1 ip address !router rip version 2 network no autosummary!router bgp 1 no synchroniza