ccnp认证考试知识：IBGP和EBGP邻居关系的建立和验证

 

r1:
in e1/0
ip add 192.168.1.1 255.255.255.0
no sh
ip route 0.0.0.0 0.0.0.0 192.168.1.2
router bgp 1
nei 192.168.2.2 remote-as 1
net 192.168.1.0
r2:
in e1/0
ip add 192.168.1.2 255.255.255.0
no sh
ip ospf 1 a 0
in e1/1
ip add 192.168.2.1 255.255.255.0
no sh
ip ospf 1 a 0
r3:
in e1/0
ip add 192.168.2.2 255.255.255.0
no sh
ip ospf 1 a 0
in e1/1
ip add 192.168.3.1 255.255.255.0
no sh
router bgp 1
nei 192.168.1.1 remote-as 1
nei 192.168.3.2 remote-as 2
net 192.168.3.0
r4:
in e1/0
ip add 192.168.3.2 255.255.255.0
http://www.luyouqiwang.com/14477/

no sh
router bgp 2
nei 192.168.3.1 remote-as 1
net 192.168.3.0

BGP是运行在运营商与运营商之间的路由协议，BGP维护着全INTERNET的路由，所以其路由条目是很多的。其复杂性也很强。废话不多说，解释一下配置的重点。
配置的重点在于R3，R3定义了IBGP邻居R1和EBGP邻居R4,是通过nei 192.168.1.1 remote-as 1定义了IBGP邻居，通过nei 192.168.3.2 remote-as 2定义了EBGP邻居。注意无论是要形成IBGP邻居还是EBGP都要有前往邻居的路由才能够形成邻居，所以我在R1和R4上各定义了一条默认路由。BGP是通过TCP端口179传输BGP消息。
验证命令：
show ip bgp 验证BGP路由，只有通过network命令定义了才会有show ip bgp sum 验证BGP邻居状态，状态不能为IDLE和ACTIVE，是数字就正常的show ip rou

 

下面是一个输出示例：
R1#show ip bgp sum
BGP router identifier 1.1.1.1, local AS number 1
BGP table version is 3, main routing table version 3
2 network entries using 234 bytes of memory
2 path entries using 104 bytes of memory
3/2 BGP path/bestpath attribute entries using 372 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP using 710 total bytes of memory
BGP activity 2/0 prefixes, 2/0 paths, scan interval 60 secs

Neighbor        V    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
192.168.2.2     4     1      42      42        3    0    0 00:38:09        1
R1形成了一个邻居关系，再看看R3的
R3#show ip bgp sum
BGP router identifier 192.168.3.1, local AS number 1
BGP table version is 4, main routing table version 4
2 network entries using 234 bytes of memory
3 path entries using 156 bytes of memory
4/2 BGP path/bestpath attribute entries using 496 bytes of memory
1 BGP AS-PATH entries using 24 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP using 910 total bytes of memory
BGP activity 2/0 prefixes, 3/0 paths, scan interval 60 secs

Neighbor        V    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
192.168.1.1     4     1      45      45        4    0    0 00:41:20        1
192.168.3.2     4     2      45      46        4    0    0 00:40:41        1

R1#show ip bgp sum
BGP router identifier 1.1.1.1, local AS number 1
BGP table version is 3, main routing table version 3
2 network entries using 234 bytes of memory
2 path entries using 104 bytes of memory
3/2 BGP path/bestpath attribute entries using 372 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP using 710 total bytes of memory
BGP activity 2/0 prefixes, 2/0 paths, scan interval 60 secs

Neighbor        V    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
192.168.2.2     4     1      42      42        3    0    0 00:38:09        1
R1#
R1#show ip bgp
BGP table version is 3, local router ID is 1.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 192.168.1.0      0.0.0.0                  0         32768 i
*>i192.168.3.0      192.168.2.2              0    100      0 i
R1#show ip ro
Codes: 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 - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route

Gateway of last resort is 192.168.1.2 to network 0.0.0.0

C    1.0.0.0/8 is directly connected, Loopback1
C    192.168.1.0/24 is directly connected, Ethernet1/0
B    192.168.3.0/24 [200/0] via 192.168.2.2, 00:39:36
S*   0.0.0.0/0 [1/0] via 192.168.1.2