BGP基本实验
一.实验拓扑图
二 实验步骤
[R1]bgp 30
[R1-bgp]router-id 1.1.1.1
[R1-bgp]peer 10.0.1.6 as-nu
[R1-bgp]peer 10.0.1.6 as-number 10
[R1-bgp]net 10.0.1.4 ?
INTEGER<0-32> Mask length of the IP address
X.X.X.X Specify an ipv4 network mask
route-policy Specify a route policy
short-cut Specify a short-cut route
<cr>
[R1-bgp]net 10.0.1.4 255.255.255.252
[R1-bgp]net 1.1.1.1 255.255.255.255
[R1-bgp]net 10.30.1.1 32
[R1-bgp]peer 10.0.1.2 as-num 40
[R1-bgp]net 10.0.1.0 255.255.255.252
[R1-bgp]
[R4]bgp 40
[R4-bgp]router-id 4.4.4.4
[R4-bgp]peer 10.0.1.1 as-num 30
[R4-bgp]peer 10.0.1.
%Aug 28 20:57:25:344 2012 R4 RM/3/RMLOG:
BGP.: 10.0.1.1 State is changed from OPENCONFIRM to ESTABLISHED.
10 as-num 10
[R4-bgp]net 10.0.1.0 30
[R4-bgp]net 10.0.1.8 30
[R4-bgp]net 4.4.4.4 32
[R4-bgp]net 10.40.4.1 32
[R4-bgp]
[R2]bgp 10
[R2-bgp]router-id 2.2.2.2
[R2-bgp]peer 10.0.1.5 as-num 30
[R2-bgp]net 2.2.2.2 32
[R2-bgp]net 10.0.1.5
%Aug 28 21:00:23:218 2012 R2 RM/3/RMLOG:
BGP.: 10.0.1.5 State is changed from OPENCONFIRM to ESTABLISHED.
[R2-bgp]undo net 10.0.1.5
[R2-bgp]net 10.0.1.4 30
[R2-bgp]undo net 2.2.2.2 32
[R2-bgp]undo net 10.0.1.4 30
[R2-bgp]peer 3.3.3.3 as-num 10
[R2-bgp]peer 3.3.3.3 connect-int lo0
[R2-bgp]peer 3.3.3.3 next-hop-local
[R2-ospf-1] default-route-advertise
[R2-ospf-1]qui
[R2]ip route 0.0.0.0 0.0.0.0 10.0.1.5
[R3]bgp 10
[R3-bgp]router-id 3.3.3.3
[R3-bgp]
[R3-bgp]peer 10.0.1.9 as-num 40
[R3-bgp]peer 2.2.2.2 as-num
%Aug 28 21:12:13:828 2012 R3 RM/3/RMLOG:
BGP.: 10.0.1.9 State is changed from OPENCONFIRM to ESTABLISHED.
10
^
% Unrecognized command found at '^' position.
[R3-bgp]peer 2.2.2.2 as-num 10
[R3-bgp]peer 2.2.2.2 connect-int lo0
[R3-bgp]peer 2.2.2.2 next-hop-local
[R3-bgp]
%Aug 28 21:18:58:859 2012 R3 RM/3/RMLOG:
BGP.: 2.2.2.2 State is changed from OPENCONFIRM to ESTABLISHED.
[R3-ospf-1]default-route-advertise
[R3-ospf-1]qui
[R3]ip rout 0.0.0.0 0.0.0.0 10.0.1.9
[R3]
R2上要配上一条指向外部的缺省静态路由，再配下发缺省的LSA，这样做当指向外部的链路down了，R2就不会下发缺省的LSA下去了 R3同样
EBGP 之间：R1和R2之间建立BGP邻居时如果用loopback接口，就需要配两个方向的静态路由，还要改TTL值，因为EBGP之间的默认TTL是1，即1跳
IBGP之间：R2和R3之间就不用这样，因为有IGP路由（OSPF）TTL值最大是255
为什么IBGP之间用loopback接口建立邻居，更可靠，防止物理端口down，物理端口down了就建立不起邻居了。而EBGP之间也可以用loopback接口，只是太麻烦了。
<R2>dis bgp rou
Total Number of Routes: 7
BGP Local router ID is 2.2.2.2
Status codes: * - valid, > - best, d - damped,
h - history, i - internal, s - suppressed, S - Stale
Origin : i - IGP, e - EGP, ? - incomplete
Network NextHop MED LocPrf PrefVal Path/Ogn
*> 1.1.1.1/32 10.0.1.5 0 0 30i
*> 4.4.4.4/32 10.0.1.5 0 30 40i
*> 10.0.1.0/30 10.0.1.5 0 0 30i
* 10.0.1.4/30 10.0.1.5 0 0 30i
* 10.0.1.8/30 10.0.1.5 0 30 40i
*> 10.30.1.1/32 10.0.1.5 0 0 30i
*> 10.40.4.1/32 10.0.1.5 0 30 40i
<R2>dis ip rout
Routing Tables: Public
Destinations : 22 Routes : 22
Destination/Mask Proto Pre Cost NextHop Interface
0.0.0.0/0 Static 60 0 10.0.1.5 Eth0/1/0
1.1.1.1/32 BGP 255 0 10.0.1.5 Eth0/1/0
2.2.2.2/32 Direct 0 0 127.0.0.1 InLoop0
3.3.3.3/32 OSPF 10 30 10.0.1.18 Eth0/1/2
4.4.4.4/32 BGP 255 0 10.0.1.5 Eth0/1/0
5.5.5.5/32 OSPF 10 10 10.0.1.18 Eth0/1/2
6.6.6.6/32 OSPF 10 20 10.0.1.18 Eth0/1/2
10.0.1.0/30 BGP 255 0 10.0.1.5 Eth0/1/0
10.0.1.4/30 Direct 0 0 10.0.1.6 Eth0/1/0
10.0.1.6/32 Direct 0 0 127.0.0.1 InLoop0
10.0.1.8/30 OSPF 10 40 10.0.1.18 Eth0/1/2
10.0.1.12/30 Direct 0 0 10.0.1.13 S0/2/0
10.0.1.13/32 Direct 0 0 127.0.0.1 InLoop0
10.0.1.14/32 Direct 0 0 10.0.1.14 S0/2/0
10.0.1.16/30 Direct 0 0 10.0.1.17 Eth0/1/2
10.0.1.17/32 Direct 0 0 127.0.0.1 InLoop0
10.0.1.20/30 OSPF 10 30 10.0.1.18 Eth0/1/2
10.0.1.24/30 OSPF 10 20 10.0.1.18 Eth0/1/2
10.30.1.1/32 BGP 255 0 10.0.1.5 Eth0/1/0
10.40.4.1/32 BGP 255 0 10.0.1.5 Eth0/1/0
127.0.0.0/8 Direct 0 0 127.0.0.1 InLoop0
127.0.0.1/32 Direct 0 0 127.0.0.1 InLoop0
<R2>tra -a 2.2.2.2 3.3.3.3
traceroute to 3.3.3.3(3.3.3.3) 30 hops max,40 bytes packet, press CTRL_C to break
1 10.0.1.18 4 ms 20 ms 15 ms
2 10.0.1.26 15 ms 10 ms 20 ms
3 3.3.3.3 30 ms 20 ms 10 ms
学会通过路由表分析，看是否有目标网段的路由，逐段排查。
<R5>dis ip rout
Routing Tables: Public
Destinations : 16 Routes : 16
Destination/Mask Proto Pre Cost NextHop Interface
0.0.0.0/0 O_ASE 150 1 10.0.1.17 Eth0/1/0
2.2.2.2/32 OSPF 10 10 10.0.1.17 Eth0/1/0
3.3.3.3/32 OSPF 10 20 10.0.1.26 Eth0/1/2
5.5.5.5/32 Direct 0 0 127.0.0.1 InLoop0
6.6.6.6/32 OSPF 10 10 10.0.1.26 Eth0/1/2
10.0.1.4/30 OSPF 10 20 10.0.1.17 Eth0/1/0
10.0.1.8/30 OSPF 10 30 10.0.1.26 Eth0/1/2
10.0.1.12/30 OSPF 10 1572 10.0.1.17 Eth0/1/0
10.0.1.16/30 Direct 0 0 10.0.1.18 Eth0/1/0
10.0.1.18/32 Direct 0 0 127.0.0.1 InLoop0
10.0.1.20/30 OSPF 10 20 10.0.1.26 Eth0/1/2
10.0.1.24/30 Direct 0 0 10.0.1.25 Eth0/1/2
10.0.1.25/32 Direct 0 0 127.0.0.1 InLoop0
10.10.5.1/32 Direct 0 0 127.0.0.1 InLoop0
127.0.0.0/8 Direct 0 0 127.0.0.1 InLoop0
127.0.0.1/32 Direct 0 0 127.0.0.1 InLoop0
[R6]dis ip rout
Routing Tables: Public
Destinations : 16 Routes : 16
Destination/Mask Proto Pre Cost NextHop Interface
0.0.0.0/0 O_ASE 150 1 10.0.1.21 Eth0/1/1
2.2.2.2/32 OSPF 10 20 10.0.1.25 Eth0/1/0
3.3.3.3/32 OSPF 10 10 10.0.1.21 Eth0/1/1
5.5.5.5/32 OSPF 10 10 10.0.1.25 Eth0/1/0
6.6.6.6/32 Direct 0 0 127.0.0.1 InLoop0
10.0.1.4/30 OSPF 10 30 10.0.1.25 Eth0/1/0
10.0.1.8/30 OSPF 10 20 10.0.1.21 Eth0/1/1
10.0.1.12/30 OSPF 10 1572 10.0.1.21 Eth0/1/1
10.0.1.16/30 OSPF 10 20 10.0.1.25 Eth0/1/0
10.0.1.20/30 Direct 0 0 10.0.1.22 Eth0/1/1
10.0.1.22/32 Direct 0 0 127.0.0.1 InLoop0
10.0.1.24/30 Direct 0 0 10.0.1.26 Eth0/1/0
10.0.1.26/32 Direct 0 0 127.0.0.1 InLoop0
10.10.6.1/32 Direct 0 0 127.0.0.1 InLoop0
127.0.0.0/8 Direct 0 0 127.0.0.1 InLoop0
127.0.0.1/32 Direct 0 0 127.0.0.1 InLoop0
注意R5，R6没有外部的明细路由，只有到外部的缺省路由，因为他们不是IBGP
[R6] dis bgp rout
[R6]
<R5> dis bgp rout
<R5>
<R1>dis ip rout
Routing Tables: Public
Destinations : 11 Routes : 11
Destination/Mask Proto Pre Cost NextHop Interface
1.1.1.1/32 Direct 0 0 127.0.0.1 InLoop0
4.4.4.4/32 BGP 255 0 10.0.1.2 Eth0/1/2
10.0.1.0/30 Direct 0 0 10.0.1.1 Eth0/1/2
10.0.1.1/32 Direct 0 0 127.0.0.1 InLoop0
10.0.1.4/30 Direct 0 0 10.0.1.5 Eth0/1/0
10.0.1.5/32 Direct 0 0 127.0.0.1 InLoop0
10.0.1.8/30 BGP 255 0 10.0.1.2 Eth0/1/2
10.30.1.1/32 Direct 0 0 127.0.0.1 InLoop0
10.40.4.1/32 BGP 255 0 10.0.1.2 Eth0/1/2
127.0.0.0/8 Direct 0 0 127.0.0.1 InLoop0
127.0.0.1/32 Direct 0 0 127.0.0.1 InLoop0
<R1> dis bgp rout
Total Number of Routes: 10
BGP Local router ID is 1.1.1.1
Status codes: * - valid, > - best, d - damped,
h - history, i - internal, s - suppressed, S - Stale
Origin : i - IGP, e - EGP, ? - incomplete
Network NextHop MED LocPrf PrefVal Path/Ogn
*> 1.1.1.1/32 0.0.0.0 0 0 i
*> 4.4.4.4/32 10.0.1.2 0 0 40i
* 10.0.1.6 0 10 40i
*> 10.0.1.0/30 0.0.0.0 0 0 i
* 10.0.1.2 0 0 40i
*> 10.0.1.4/30 0.0.0.0 0 0 i
*> 10.0.1.8/30 10.0.1.2 0 0 40i
*> 10.30.1.1/32 0.0.0.0 0 0 i
*> 10.40.4.1/32 10.0.1.2 0 0 40i
* 10.0.1.6 0 10 40i
R1到4.4.4.4的路由选择下一跳是10.0.1.2是由于开销
<R2>dis ip rout
Routing Tables: Public
Destinations : 23 Routes : 23
Destination/Mask Proto Pre Cost NextHop Interface
0.0.0.0/0 Static 60 0 10.0.1.5 Eth0/1/0
1.1.1.1/32 BGP 255 0 10.0.1.5 Eth0/1/0
2.2.2.2/32 Direct 0 0 127.0.0.1 InLoop0
3.3.3.3/32 OSPF 10 30 10.0.1.18 Eth0/1/2
4.4.4.4/32 BGP 255 0 3.3.3.3 Eth0/1/2
5.5.5.5/32 OSPF 10 10 10.0.1.18 Eth0/1/2
6.6.6.6/32 OSPF 10 20 10.0.1.18 Eth0/1/2
10.0.1.0/30 BGP 255 0 10.0.1.5 Eth0/1/0
10.0.1.4/30 Direct 0 0 10.0.1.6 Eth0/1/0
10.0.1.6/32 Direct 0 0 127.0.0.1 InLoop0
10.0.1.8/30 OSPF 10 40 10.0.1.18 Eth0/1/2
10.0.1.12/30 Direct 0 0 10.0.1.13 S0/2/0
10.0.1.13/32 Direct 0 0 127.0.0.1 InLoop0
10.0.1.14/32 Direct 0 0 10.0.1.14 S0/2/0
10.0.1.16/30 Direct 0 0 10.0.1.17 Eth0/1/2
10.0.1.17/32 Direct 0 0 127.0.0.1 InLoop0
10.0.1.20/30 OSPF 10 30 10.0.1.18 Eth0/1/2
10.0.1.24/30 OSPF 10 20 10.0.1.18 Eth0/1/2
10.10.6.1/32 OSPF 10 20 10.0.1.18 Eth0/1/2
10.30.1.1/32 BGP 255 0 10.0.1.5 Eth0/1/0
10.40.4.1/32 BGP 255 0 3.3.3.3 Eth0/1/2
127.0.0.0/8 Direct 0 0 127.0.0.1 InLoop0
127.0.0.1/32 Direct 0 0 127.0.0.1 InLoop0
<R2>dis bgp rout
Total Number of Routes: 10
BGP Local router ID is 2.2.2.2
Status codes: * - valid, > - best, d - damped,
h - history, i - internal, s - suppressed, S - Stale
Origin : i - IGP, e - EGP, ? - incomplete
Network NextHop MED LocPrf PrefVal Path/Ogn
*> 1.1.1.1/32 10.0.1.5 0 0 30i
*>i 4.4.4.4/32 3.3.3.3 0 100 0 40i
* 10.0.1.5 0 30 40i
*> 10.0.1.0/30 10.0.1.5 0 0 30i
* i 3.3.3.3 0 100 0 40i
* 10.0.1.4/30 10.0.1.5 0 0 30i
* 10.0.1.8/30 10.0.1.5 0 30 40i
*> 10.30.1.1/32 10.0.1.5 0 0 30i
*>i 10.40.4.1/32 3.3.3.3 0 100 0 40i
* 10.0.1.5 0 30 40i
