一 拓扑说明
R1、R2、R3通过ospf建立邻居，R1和R3通过非直连物理接口建立EBGP邻居
注意：默认情况下,BGP认为EBGP邻居是直连可达的。如果EBGP邻居间不是直连可达，则必须在BGP视图下配置允许同非直接相连网络上的邻居建立EBGP连接。
二 R1和R3设备配置
1.R1配置
router bgp 100
bgp log-neighbor-changes
bgp graceful-restart restart-time 120
bgp graceful-restart stalepath-time 360
bgp graceful-restart
neighbor 2.2.2.2 remote-as 200
neighbor 2.2.2.2 ebgp-multihop 255
address-family ipv4
neighbor 2.2.2.2 activate
exit-address-family
!
2.R3配置
router bgp 200
bgp log-neighbor-changes
bgp graceful-restart restart-time 120
bgp graceful-restart stalepath-time 360
bgp graceful-restart
neighbor 1.1.1.1 remote-as 100
neighbor 1.1.1.1 ebgp-multihop 255
address-family ipv4
neighbor 1.1.1.1 activate
exit-address-family
!
三 前后对比
3.1 R1、R3配置非直连ebgp邻居多条功能前-邻居无法建立-路由无法学习
R1#sh bgp all su//邻居状态不对
For address family: IPv4 Unicast
BGP router identifier 192.168.1.1, local AS number 100
BGP table version is 1
0 BGP AS-PATH entries
0 BGP Community entries
0 BGP Prefix entries (Maximum-prefix:4294967295)
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
2.2.2.2 4 200 0 0 0 0 0 never Idle
Total number of neighbors 1, established neighbors 0
R1#
R1#
R1#sh ip ro//没有路由
Codes: C - Connected, L - Local, S - Static
R - RIP, O - OSPF, B - BGP, I - IS-IS, V - Overflow route
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
SU - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
IA - Inter area, EV - BGP EVPN, A - Arp to host
LA - Local aggregate route
* - candidate default
Gateway of last resort is no set
C 1.1.1.0/30 is directly connected, GigabitEthernet 0/0
C 1.1.1.1/32 is local host.
O 2.2.2.0/30 [110/2] via 1.1.1.2, 00:04:44, GigabitEthernet 0/0
C 192.168.1.1/32 is local host.
R1#
R1#sh bgp ipv4 unicast
R1#
3.2 R1、R3配置非直连ebgp邻居多条功能后-邻居正常建立-路由可以学习
R1#sh bgp all su//邻居正常
For address family: IPv4 Unicast
BGP router identifier 192.168.1.1, local AS number 100
BGP table version is 3
2 BGP AS-PATH entries
0 BGP Community entries
2 BGP Prefix entries (Maximum-prefix:4294967295)
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
2.2.2.2 4 200 7 5 3 0 0 00:03:191
Total number of neighbors 1, established neighbors 1
R1#
R1#sh ip ro//路由学习正常
Codes: C - Connected, L - Local, S - Static
R - RIP, O - OSPF, B - BGP, I - IS-IS, V - Overflow route
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
SU - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
IA - Inter area, EV - BGP EVPN, A - Arp to host
LA - Local aggregate route
* - candidate default
Gateway of last resort is no set
C 1.1.1.0/30 is directly connected, GigabitEthernet 0/0
C 1.1.1.1/32 is local host.
O 2.2.2.0/30 [110/2] via 1.1.1.2, 00:11:56, GigabitEthernet 0/0
C 192.168.1.1/32 is local host.
B 192.168.11.1/32 [20/0] via 2.2.2.2, 00:00:15
R1#
R1#sh bgp ipv4 unicast//路由学习正常
BGP table version is 3, local router ID is 192.168.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
S Stale, b - backup entry, m - multipath, f Filter, a additional-path
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 192.168.1.1/32 0.0.0.0 0 32768 i
*> 192.168.11.1/32 2.2.2.2 0 0 200 i
Total number of prefixes 2
R1#
