【正文】 cd 4 2 5 5 1 0 0 00:02:07 0鄰居關系正常建立3. Bgp fastexternalfalloveru 現(xiàn)在關閉R1的fastethernet 0/0R1(configrouter)interface fastethernet 0/0R1(configif)shutdownu 查看R1鄰居關系建立情況R1(configif)do show ip bgp summary BGP router identifier , local AS number 1BGP table version is 1, main routing table version 1Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 4 2 6 6 0 0 0 00:00:27 Idle發(fā)現(xiàn)鄰居關系馬上就down了u 現(xiàn)在開啟fastethernet 0/0R1(configrouter)interface fastethernet 0/0R1(configif)no shutdownu 使用no bgp fastexternalfallover，這樣在保持時間內鄰居關系不會關閉，不管鄰居是不是關閉狀態(tài)R2(configrouter)no bgp fastexternalfalloveru 關掉R1 的fastethernet 0/0口R1(configrouter)interface fastethernet 0/0R1(configif)shutdownu 查看R2，BGP鄰居關系R2(configrouter)do show ip bgp summary BGP router identifier , local AS number 2BGP table version is 1, main routing table version 1Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 4 1 12 14 1 0 0 00:02:39 0鄰居關系仍保持u 查看R1R1(configif)do show ip bgp summaryBGP router identifier , local AS number 1BGP table version is 1, main routing table version 1Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 4 2 12 12 0 0 0 00:01:38 Idle鄰居關系down掉總結：bgp fastexternalfallover 默認是打開的，意思是如果鄰居關閉，就會切斷鄰居關系。如果no 掉，那么在保持時間內會一直保持鄰居關系，而不管對方是不是down了六、 手工設置路由器的ID1. 要點解釋l Bgp routerid ipaddress路由器的ID順序：手工設置，環(huán)回接口最高，最后是物理接口最高的ip地址。注意：設置路由器ID最大的好處就是可以人為的控制路由器ID號，建議手工設置2. 實驗拓撲3. 配置216。 R1：R1enable R1configure terminal R1(config)interface serial 0/0R1(configif)no shutdown R1(configif)ip address R1(configif)router bgp 1R1(configrouter)neighbor remoteas 2216。 R2：R2enable R2configure terminal R2(config)interface serial 0/0R2(configif)no shutdown R2(configif)ip address R2(configif)router bgp 2R2(configrouter)neighbor remoteas 14. 物理地址作為路由器IDu 查看R1路由器IDR1(configrouter)do show ip bgp neighborBGP neighbor is , remote AS 2, external link BGP version 4, remote router ID BGP state = Established, up for 00:01:24 Last read 00:00:24, last write 00:00:24, hold time is 180, keepalive interval is 60 seconds Neighbor capabilities: Route refresh: advertised and received(old amp。 new)Address family IPv4 Unicast: advertised and receivedu 查看R2路由器IDR2(configrouter)do show ip bgp neighborBGP neighbor is , remote AS 1, external link BGP version 4, remote router ID BGP state = Established, up for 00:02:16 Last read 00:00:16, last write 00:00:16, hold time is 180, keepalive interval is 60 seconds Neighbor capabilities: Route refresh: advertised and received(old amp。 new) Address family IPv4 Unicast: advertised and received可以看到時物理接口作為路由器ID5. 設置環(huán)回接口使其作為路由器IDu 配置R1(configrouter)interface loopback 0R1(configif)ip address R1(configif)do clear ip bgp *u 查看路由器IDR2(configrouter)do show ip bgp neighborBGP neighbor is , remote AS 1, external link BGP version 4, remote router ID BGP state = Established, up for 00:00:37 Last read 00:00:37, last write 00:00:37, hold time is 180, keepalive interval is 60 seconds Neighbor capabilities: Route refresh: advertised and received(old amp。 new) Address family IPv4 Unicast: advertised and received6. 手工改變路由器IDu 配置R1(configif)router bgp 1R1(configrouter)bgp rouR1(configrouter)bgp routerid u 查看路由器IDR1(configrouter)do show ip bgp summaryBGP router identifier , local AS number 1BGP table version is 1, main routing table version 1Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 4 2 19 19 1 0 0 00:00:43 0路由器ID改變后，鄰居關系重新建立，并且路由器ID馬上就改變了，該方法可人為控制路由器ID號七、 修改BGP的觸發(fā)時間1. 要點解釋l Neighbor ip address/peergroupname advertisementinterval seconds 如果鄰居是ibgp則修改ibgp時間，如果鄰居時ebgp則會修改ebgp時間。默認情況下，ibgp為5秒，ebgp為30秒。這是路由更新的最少時間。 原因：當路由條目在一定時間閃動多次時，也只有到了最少觸發(fā)時間才會觸發(fā)更新。2. 實驗拓撲3. 配置216。 R1：R1enable R1configure terminal R1(config)interface serial 0/0R1(configif)no shutdown R1(configif)ip address R1(configif)router bgp 1R1(configrouter)neighbor remoteas 1216。 R2：R2enable R2configure terminal R2(config)interface serial 0/0R2(configif)no shutdown R2(configif)ip address R2(configif)interface serial 0/1R2(configif)no shutdown R2(configif)ip address R2(configif)router bgp 1R2(configrouter)neighbor remoteas 1R2(configrouter)neighbor remoteas 2216。 R3：R3enable R3configure terminal R3(config)interface serial 0/0R3(configif)no shutdown R3(configif)ip address R3(configif)router bgp 2R3(configrouter)neighbor remoteas 14. 驗證u 查看BGP鄰居是否建立R2(configrouter)do show ip bgp summaryBGP router identifier , local AS number 1BGP table version is 1, main routing table version 1Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 4 1 5 5 1 0 0 00:02:16 0 4 2 4 4 1 0 0 00:00:44 0u 查看一下觸發(fā)時間R2(configrouter)do show ip bgp neighborBGP neighbor is , remote AS 1, internal link BGP version 4, remote router ID BGP state = Established, up for 00:06:02 Last read 00:00:02, last write 00:00:02, hold time is 180, keepalive interval is 60 seconds Neighbor capabilities: Route refresh: advertised and received(old amp。 new) Address family IPv4 Unicast: advertised and received Message statistics: InQ depth is 0 OutQ depth is 0 Sent Rcvd O