【转】BGP基本配置与总结 (二)

【转】BGP基本配置与总结 (二)

使用BGP路由协议的意义是将自治系统中的路由通告到外部，而自治系统内使用的是IGP路由，这就是为什么内部BGP管理距离这么高，而外部BGP管理距离这么低的原因了。

1、建立BGP邻居的前提：在BGP的neighbor中指定的IP必须是可达对方的，不是使用直连接口的，可以通过静态路由、动态路由来到达指定的IP。

2、通告BGP网络即network：邻居建立完成后，就可以使用bgp通告本地网络了。在ibgp中使用其他的动态路由协议（如eigrp、ospf等)，是为了第1步中做neighbor的IP可达而已。

3、必须修改BGP下一跳。

4、BGP同步规则，当启动同步情况下BGP路由器不应使用通过IBGP获悉的路由或将其通告给外部邻居，除非该路由是本地的或通过IBGP获悉的(注意“通过IBGP获悉”指的是当BGP与IGP同步情况下，即在该自治系统中BGP与IGP同时都通告了该路由，那么BGP路由器就可以将该路由通告到外部邻居。）。当禁用同步的情况下全互联IBGP拓扑就可以将从IBGP路由器获悉的路由通告给外部BGP。

实验：

实验拓扑：



1）验证neighbor中对方的IP不可达时，无法建立邻居关系（R2与R3)。

R2(config-router)#do sh run

router bgp 65001

no synchronization

bgp log-neighbor-changes

network 2.2.2.2 mask 255.255.255.255

network 10.1.1.0 mask 255.255.255.0

neighbor 3.3.3.3 remote-as 65001

neighbor 3.3.3.3 update-source Loopback0 //指本身的源地址接口

no auto-summary

R3(config-router)#do sh run

router bgp 65001

no synchronization

bgp log-neighbor-changes

network 3.3.3.3 mask 255.255.255.255

network 10.1.1.0 mask 255.255.255.0

neighbor 2.2.2.2 remote-as 65001

neighbor 2.2.2.2 update-source Loopback0

no auto-summary

在检查建立邻居结果（R2）：

R2(config-router)#do sh ip bgp nei

BGP neighbor is 3.3.3.3, remote AS 65001, internal link

BGP version 4, remote router ID 0.0.0.0

BGP state = Active

Last read 00:02:37, last write 00:02:37, hold time is 180, keepalive interval is 60 seconds

Message statistics:

InQ depth is 0

OutQ depth is 0

Sent Rcvd

Opens: 0 0

Notifications: 0 0

Updates: 0 0

Keepalives: 0 0

Route Refresh: 0 0

Total: 0 0

Default minimum time between advertisement runs is 0 seconds

For address family: IPv4 Unicast

BGP table version 1, neighbor version 0/0

Output queue size : 0

Index 1, Offset 0, Mask 0x2

1 update-group member

Sent Rcvd

Prefix activity: —- —-

Prefixes Current: 0 0

Prefixes Total: 0 0

Implicit Withdraw: 0 0

Explicit Withdraw: 0 0

Used as bestpath: n/a 0

Used as multipath: n/a 0

Outbound Inbound

Local Policy Denied Prefixes: ——– ——-

Total: 0 0

Number of NLRIs in the update sent: max 0, min 0

Connections established 0; dropped 0 \\established为0表明没有建立邻居关系。

Last reset never

No active TCP connection

R2(config-router)#do sh ip bgp \\同时没有显示邻居拓扑表

BGP table version is 3, local router ID is 22.22.22.22

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

*> 2.2.2.2/32 0.0.0.0 0 32768 i

*> 10.1.1.0/24 0.0.0.0 0 32768 i

R2(config-router)#

建立邻居失败是由于R2与R3的环回接口IP相对是未知（不可达的）。

如果使用的是10.1.1.0/24作为建立邻居的网段，则R2 与R3邻居建立成功。

R2(config-router)#do sh run

router bgp 65001

no synchronization

bgp log-neighbor-changes

network 2.2.2.2 mask 255.255.255.255

network 10.1.1.0 mask 255.255.255.0

neighbor 10.1.1.2 remote-as 65001

R3(config-router)# do sh run

router bgp 65001

no synchronization

bgp log-neighbor-changes

network 3.3.3.3 mask 255.255.255.255

network 10.1.1.0 mask 255.255.255.0

neighbor 10.1.1.1 remote-as 65001

no auto-summary

R2(config-router)#do sh

*Mar 1 00:29:20.323: %BGP-5-ADJCHANGE: neighbor 10.1.1.2 Up

R2(config-router)#do sh bgp nei

BGP neighbor is 10.1.1.2, remote AS 65001, internal link

BGP version 4, remote router ID 33.33.33.33

BGP state = Established, up for 00:00:04

Last read 00:00:04, last write 00:00:04, hold time is 180, keepalive interval is 60 seconds

Neighbor capabilities:

Route refresh: advertised and received(old & new)

Address family IPv4 Unicast: advertised and received

Message statistics:

InQ depth is 0

OutQ depth is 0

Sent Rcvd

Opens: 1 1

Notifications: 0 0

Updates: 1 1

Keepalives: 3 3

Route Refresh: 0 0

Total: 5 5

Default minimum time between advertisement runs is 0 seconds

For address family: IPv4 Unicast

BGP table version 6, neighbor version 6/0

Output queue size : 0

Index 1, Offset 0, Mask 0x2

1 update-group member

Sent Rcvd

Prefix activity: —- —-

Prefixes Current: 2 2 (Consumes 104 bytes)

Prefixes Total: 2 2

Implicit Withdraw: 0 0

Explicit Withdraw: 0 0

Used as bestpath: n/a 1

Used as multipath: n/a 0

Outbound Inbound

Local Policy Denied Prefixes: ——– ——-

Bestpath from this peer: 1 n/a

Total: 1 0

Number of NLRIs in the update sent: max 2, min 2

Connections established 1; dropped 0 \\表明邻居关系建立成功。

Last reset never

Connection state is ESTAB, I/O status: 1, unread input bytes: 0

Connection is ECN Disabled, Mininum incoming TTL 0, Outgoing TTL 255

Local host: 10.1.1.1, Local port: 14656

Foreign host: 10.1.1.2, Foreign port: 179

Enqueued packets for retransmit: 0, input: 0 mis-ordered: 0 (0 bytes)

Event Timers (current time is 0x1AF6DC):

Timer Starts Wakeups Next

Retrans 5 0 0x0

TimeWait 0 0 0x0

AckHold 3 1 0x0

SendWnd 0 0 0x0

KeepAlive 0 0 0x0

GiveUp 0 0 0x0

PmtuAger 0 0 0x0

DeadWait 0 0 0x0

iss: 1178971408 snduna: 1178971571 sndnxt: 1178971571 sndwnd: 16222

irs: 3142416282 rcvnxt: 3142416445 rcvwnd: 16222 delrcvwnd: 162

SRTT: 148 ms, RTTO: 1301 ms, RTV: 1153 ms, KRTT: 0 ms

minRTT: 60 ms, maxRTT: 316 ms, ACK hold: 200 ms

Flags: active open, nagle

IP Precedence value : 6

Datagrams (max data segment is 1460 bytes):

Rcvd: 5 (out of order: 0), with data: 3, total data bytes: 162

Sent: 7 (retransmit: 0, fastretransmit: 0, partialack: 0, Second Congestion: 0), with data: 4, total data bytes: 162

R2(config-router)# do sh ip bgp

BGP table version is 6, local router ID is 22.22.22.22

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

*> 2.2.2.2/32 0.0.0.0 0 32768 i

*>i3.3.3.3/32 10.1.1.2 0 100 0 i

* i10.1.1.0/24 10.1.1.2 0 100 0 i

*> 0.0.0.0 0 32768 i

R2(config-router)#do sh ip rou

Gateway of last resort is not set

2.0.0.0/32 is subnetted, 1 subnets

C 2.2.2.2 is directly connected, Loopback0

100.0.0.0/24 is subnetted, 1 subnets

C 100.1.1.0 is directly connected, Serial0/0

3.0.0.0/32 is subnetted, 1 subnets

B 3.3.3.3 [200/0] via 10.1.1.2, 00:00:55

22.0.0.0/32 is subnetted, 1 subnets

C 22.22.22.22 is directly connected, Loopback1

10.0.0.0/24 is subnetted, 1 subnets

C 10.1.1.0 is directly connected, Serial0/1

R2(config-router)#

在实际操作中经常使用环回接口作为建立邻居的源地址，所以IBGP中通常使用静态路由或动态路由协议将环回接口及不直连的路由器网段先配置可达，之后再建立IBGP邻居关系。以IBGP与OSPF为例：

R2(config-router)#do sh run

!

router ospf 1

log-adjacency-changes

network 2.2.2.2 0.0.0.0 area 0

network 10.1.1.0 0.0.0.255 area 0

network 22.22.22.22 0.0.0.0 area 0

!

router bgp 65001

no synchronization

bgp log-neighbor-changes

network 2.2.2.2 mask 255.255.255.255

network 10.1.1.0 mask 255.255.255.0

neighbor 3.3.3.3 remote-as 65001

neighbor 3.3.3.3 update-source Loopback0

no auto-summary

R3(config-router)#do sh run

!

router ospf 1

log-adjacency-changes

network 3.3.3.3 0.0.0.0 area 0

network 10.1.1.0 0.0.0.255 area 0

network 33.33.33.33 0.0.0.0 area 0

!

router bgp 65001

no synchronization

bgp log-neighbor-changes

network 3.3.3.3 mask 255.255.255.255

network 10.1.1.0 mask 255.255.255.0

neighbor 2.2.2.2 remote-as 65001

neighbor 2.2.2.2 update-source Loopback0

no auto-summary

IBGP邻居成功建立后结果：

R2(config-router)#do sh ip bgp

Connections established 1; dropped 0 \\建立邻居成功。

Last reset never

R2(config-router)#do sh ip rou

2.0.0.0/32 is subnetted, 1 subnets

C 2.2.2.2 is directly connected, Loopback0

100.0.0.0/24 is subnetted, 1 subnets

C 100.1.1.0 is directly connected, Serial0/0

33.0.0.0/32 is subnetted, 1 subnets

O 33.33.33.33 [110/65] via 10.1.1.2, 00:00:44, Serial0/1

3.0.0.0/32 is subnetted, 1 subnets

O 3.3.3.3 [110/65] via 10.1.1.2, 00:00:44, Serial0/1

22.0.0.0/32 is subnetted, 1 subnets

C 22.22.22.22 is directly connected, Loopback1

10.0.0.0/24 is subnetted, 1 subnets

C 10.1.1.0 is directly connected, Serial0/1

R2(config-router)#

在IBGP中使用OSPF后，路由表中没有显示相关BGP路由，由于IBGP管理距离200，而OSPF管理距离为110，所以同一路由下使用OSPF。那为什么在router bgp 65001协议中还要通告本地路由器的网段呢？这主要为了通告给外部EBGP自治系统而用，如果只在OSPF协议中通告，外部EBGP是无法可达65001这个自治系统的。

与外部EBGP建立关系：

R1(config-router)#do sh run

router bgp 65002

no synchronization

bgp log-neighbor-changes

network 1.1.1.1 mask 255.255.255.255

network 11.11.11.11 mask 255.255.255.255

network 100.1.1.0 mask 255.255.255.0

neighbor 100.1.1.2 remote-as 65001

no auto-summary

R2(config-router)#do sh run

router ospf 1

log-adjacency-changes

network 2.2.2.2 0.0.0.0 area 0

network 10.1.1.0 0.0.0.255 area 0

network 22.22.22.22 0.0.0.0 area 0

!

router bgp 65001

no synchronization

bgp log-neighbor-changes

network 2.2.2.2 mask 255.255.255.255

network 10.1.1.0 mask 255.255.255.0

neighbor 3.3.3.3 remote-as 65001

neighbor 3.3.3.3 update-source Loopback0

neighbor 100.1.1.1 remote-as 65002

no auto-summary

!

检查结果：

R1(config-router)#do sh ip rou

1.0.0.0/32 is subnetted, 1 subnets

C 1.1.1.1 is directly connected, Loopback0

2.0.0.0/32 is subnetted, 1 subnets

B 2.2.2.2 [20/0] via 100.1.1.2, 00:01:08

100.0.0.0/24 is subnetted, 1 subnets

C 100.1.1.0 is directly connected, Serial0/0

3.0.0.0/32 is subnetted, 1 subnets

B 3.3.3.3 [20/0] via 100.1.1.2, 00:01:08

10.0.0.0/24 is subnetted, 1 subnets

B 10.1.1.0 [20/0] via 100.1.1.2, 00:01:08

11.0.0.0/32 is subnetted, 1 subnets

C 11.11.11.11 is directly connected, Loopback1

\\外部自治系统R1中没有看到R2中22.22.22.22及R3的33.33.33.33路由

R1(config-router)# do sh ip bgp

Network Next Hop Metric LocPrf Weight Path

*> 1.1.1.1/32 0.0.0.0 0 32768 i

*> 2.2.2.2/32 100.1.1.2 0 0 65001 i

*> 3.3.3.3/32 100.1.1.2 0 65001 i

*> 10.1.1.0/24 100.1.1.2 0 0 65001 i

*> 11.11.11.11/32 0.0.0.0 0 32768 i

*> 100.1.1.0/24 0.0.0.0 0 32768 i

R1(config-router)#

可以看出因没有在IBGP协议中通告22.22.22.22及33.33.33.33，从而外部EBGP路由表中没有相关路由。将这两条路由在各自本地路由器上的IBGP协议通告后，外部EBGP路由表显示。

R1(config)#do sh ip rou

1.0.0.0/32 is subnetted, 1 subnets

C 1.1.1.1 is directly connected, Loopback0

2.0.0.0/32 is subnetted, 1 subnets

B 2.2.2.2 [20/0] via 100.1.1.2, 00:11:46

100.0.0.0/24 is subnetted, 1 subnets

C 100.1.1.0 is directly connected, Serial0/0

33.0.0.0/32 is subnetted, 1 subnets

B 33.33.33.33 [20/0] via 100.1.1.2, 00:02:36

3.0.0.0/32 is subnetted, 1 subnets

B 3.3.3.3 [20/0] via 100.1.1.2, 00:11:46

22.0.0.0/32 is subnetted, 1 subnets

B 22.22.22.22 [20/0] via 100.1.1.2, 00:03:11

10.0.0.0/24 is subnetted, 1 subnets

B 10.1.1.0 [20/0] via 100.1.1.2, 00:11:47

11.0.0.0/32 is subnetted, 1 subnets

C 11.11.11.11 is directly connected, Loopback1

R1(config)#

3)BGP下一跳属性

就EBGP而言，下一跳地址就是发送更新的邻居路由器的IP地址。

然而，IBGP规定，应在IBGP中通告EBGP通告的下一跳。从拓扑图中我们 知道R3要到达R1网络，必须经过R2，但我们查看R3的BGP表发现

R3(config-router)#do sh ip bgp

BGP table version is 29, local router ID is 33.33.33.33

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

* i1.1.1.1/32 100.1.1.1 0 100 0 65002 i \\显然R3下一跳直接是R1的接口，说明下一跳错误的。

r>i2.2.2.2/32 2.2.2.2 0 100 0 i

*> 3.3.3.3/32 0.0.0.0 0 32768 i

* i10.1.1.0/24 2.2.2.2 0 100 0 i

*> 0.0.0.0 0 32768 i

* i11.11.11.11/32 100.1.1.1 0 100 0 65002 i

r>i22.22.22.22/32 2.2.2.2 0 100 0 i

*> 33.33.33.33/32 0.0.0.0 0 32768 i

* i100.1.1.0/24 100.1.1.1 0 100 0 65002 i

所以要修改这下一跳，由于此路由是在R2上通告的，所以在R2上BGP协议上添加如下命令neighbor 3.3.3.3 next-hop-self，结果R3通往R1的下一跳正常

R3(config-router)#do sh ip bgp

BGP table version is 32, local router ID is 33.33.33.33

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

* i1.1.1.1/32 2.2.2.2 0 100 0 65002 i \\表明正常。

r>i2.2.2.2/32 2.2.2.2 0 100 0 i

*> 3.3.3.3/32 0.0.0.0 0 32768 i

* i10.1.1.0/24 2.2.2.2 0 100 0 i

*> 0.0.0.0 0 32768 i

* i11.11.11.11/32 2.2.2.2 0 100 0 65002 i

r>i22.22.22.22/32 2.2.2.2 0 100 0 i

*> 33.33.33.33/32 0.0.0.0 0 32768 i

* i100.1.1.0/24 2.2.2.2 0 100 0 65002 i

R3(config-router)#

4）BGP同步实验

从R1的路由表可以看到到达R3的所有路由3.3.3.3等，但从R1却ping不能3.3.3.3，为什么呢？

R1#tracerou 3.3.3.3

Type escape sequence to abort.

Tracing the route to 3.3.3.3

1 100.1.1.2 24 msec 48 msec 16 msec

2 * * *

3 * * *

4 * * *

5 * *

再看R3上路由表及BGP表

R3#sh ip rou

2.0.0.0/32 is subnetted, 1 subnets

O 2.2.2.2 [110/65] via 10.1.1.1, 00:55:57, Serial0/1

33.0.0.0/32 is subnetted, 1 subnets

C 33.33.33.33 is directly connected, Loopback1

3.0.0.0/32 is subnetted, 1 subnets

C 3.3.3.3 is directly connected, Loopback0

22.0.0.0/32 is subnetted, 1 subnets

O 22.22.22.22 [110/65] via 10.1.1.1, 00:55:57, Serial0/1

10.0.0.0/24 is subnetted, 1 subnets

C 10.1.1.0 is directly connected, Serial0/1

R3#

R3#sh ip bgp

BGP table version is 8, local router ID is 33.33.33.33

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

* i1.1.1.1/32 2.2.2.2 0 100 0 65002 i

r>i2.2.2.2/32 2.2.2.2 0 100 0 i

*> 3.3.3.3/32 0.0.0.0 0 32768 i

* i10.1.1.0/24 2.2.2.2 0 100 0 i

*> 0.0.0.0 0 32768 i

* i11.11.11.11/32 2.2.2.2 0 100 0 65002 i

r>i22.22.22.22/32 2.2.2.2 0 100 0 i

*> 33.33.33.33/32 0.0.0.0 0 32768 i

* i100.1.1.0/24 2.2.2.2 0 100 0 65002 i

从R3的BGP表可以看出它已经获悉到达R1的路由了，但却没有将路由加入到路由表中，原因是R3是通过R2即IBGP获悉的路由，按BGP规则R3不能使用通过IBGP路由器获悉的路由（不管是启动或禁用同步，自治系统中只要运行BGP协议的路由器的BGP表都是一样的。所以当BGP路由器ASBR从外部获悉的路由后都会在自治系统中通告，而自治系统内的IBGP路由器都会收到BGP路由器ASBR通告的外部路由，但只保存在BGP表中，而不会将其加入到路由表中，即无效路由，因此哪个路由器把同步关闭，那么那个IBGP路由器就可以将外部路由加入到路由表中）。

3.1、启动同步（不推荐）后，只有当BGP与IGP同步了路由（这里的同步是指将BGP重分发必到IGP中,比如在中转路径自治系统中BGP表获悉了多个自治系统的外来路由，然而这些外来路由没有同步到IGP中即没有重分发到IGP中，那么这些外来路由不会被中转路径自治系统中的IBGP路由器所通告，就像来例中ospf没有通告33.33.33.33时一样。这种方法如果有大量外来路由情况下，就不好操作，汇聚慢等，不推荐使用）），其他IBGP路由器才会将从IBGP获悉的路由通告到外部邻居。

从ospf中删除33.33.33.33的通告后，R1的BGP表及路由表如下

R1#sh ip bgp

Network Next Hop Metric LocPrf Weight Path

*> 1.1.1.1/32 0.0.0.0 0 32768 i

*> 2.2.2.2/32 100.1.1.2 0 0 65001 i

*> 3.3.3.3/32 100.1.1.2 0 65001 i

*> 10.1.1.0/24 100.1.1.2 0 0 65001 i

*> 11.11.11.11/32 0.0.0.0 0 32768 i

*> 22.22.22.22/32 100.1.1.2 0 0 65001 i

*> 100.1.1.0/24 0.0.0.0 0 32768 i

R1#sh ip rou

1.0.0.0/32 is subnetted, 1 subnets

C 1.1.1.1 is directly connected, Loopback0

2.0.0.0/32 is subnetted, 1 subnets

B 2.2.2.2 [20/0] via 100.1.1.2, 01:35:26

100.0.0.0/24 is subnetted, 1 subnets

C 100.1.1.0 is directly connected, Serial0/0

3.0.0.0/32 is subnetted, 1 subnets

B 3.3.3.3 [20/0] via 100.1.1.2, 01:35:26

22.0.0.0/32 is subnetted, 1 subnets

B 22.22.22.22 [20/0] via 100.1.1.2, 01:35:26

10.0.0.0/24 is subnetted, 1 subnets

B 10.1.1.0 [20/0] via 100.1.1.2, 01:35:27

11.0.0.0/32 is subnetted, 1 subnets

C 11.11.11.11 is directly connected, Loopback1

R2的BGP表

R2#sh ip bgp

Network Next Hop Metric LocPrf Weight Path

*> 1.1.1.1/32 100.1.1.1 0 0 65002 i

*> 2.2.2.2/32 0.0.0.0 0 32768 i

r>i3.3.3.3/32 3.3.3.3 0 100 0 i

* i10.1.1.0/24 3.3.3.3 0 100 0 i

*> 0.0.0.0 0 32768 i

*> 11.11.11.11/32 100.1.1.1 0 0 65002 i

*> 22.22.22.22/32 0.0.0.0 0 32768 i

* i33.33.33.33/32 3.3.3.3 0 100 0 i

r> 100.1.1.0/24 100.1.1.1 0 0 65002 i

R2#

可以看到由于bgp与ospf中33.33.33.33这条路由没有同步，所以R2即便BGP表中有33.33.33.33也不会通告到外部邻居，而其他同步的路由则通告。

3.2、禁用同步（推荐）后，BGP路由器可使用从IBGP获悉的路由或将其通告给外部邻居，即便BGP与IGP没有同步的情况下。在R2上的BGP中关闭同步no synchronization,则R1可收到33.33.33.33的通告。

R1#sh ip bgp

BGP table version is 35, local router ID is 11.11.11.11

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

*> 1.1.1.1/32 0.0.0.0 0 32768 i

*> 2.2.2.2/32 100.1.1.2 0 0 65001 i

*> 3.3.3.3/32 100.1.1.2 0 65001 i

*> 10.1.1.0/24 100.1.1.2 0 0 65001 i

*> 11.11.11.11/32 0.0.0.0 0 32768 i

*> 22.22.22.22/32 100.1.1.2 0 0 65001 i

*> 33.33.33.33/32 100.1.1.2 0 65001 i \\在R3的BGP通告而OSPF上没有通告。

*> 100.1.1.0/24 0.0.0.0 0 32768 i

这样之后我们在R3上关闭BGP同步no synchronization，使R3能够将R2通告的路由加入到路由表中。

R3(config-router)#do sh ip bgp

Network Next Hop Metric LocPrf Weight Path

*>i1.1.1.1/32 2.2.2.2 0 100 0 65002 i \\表明已成功加入路由表中

r>i2.2.2.2/32 2.2.2.2 0 100 0 i

*> 3.3.3.3/32 0.0.0.0 0 32768 i

* i10.1.1.0/24 2.2.2.2 0 100 0 i

*> 0.0.0.0 0 32768 i

*>i11.11.11.11/32 2.2.2.2 0 100 0 65002 i

r>i22.22.22.22/32 2.2.2.2 0 100 0 i

*> 33.33.33.33/32 0.0.0.0 0 32768 i

*>i100.1.1.0/24 2.2.2.2 0 100 0 65002 i

R3(config-router)#

R3(config-router)#do sh ip rou

1.0.0.0/32 is subnetted, 1 subnets

B 1.1.1.1 [200/0] via 2.2.2.2, 00:01:37

2.0.0.0/32 is subnetted, 1 subnets

O 2.2.2.2 [110/65] via 10.1.1.1, 00:31:24, Serial0/1

100.0.0.0/24 is subnetted, 1 subnets

B 100.1.1.0 [200/0] via 2.2.2.2, 00:01:37

33.0.0.0/32 is subnetted, 1 subnets

C 33.33.33.33 is directly connected, Loopback1

3.0.0.0/32 is subnetted, 1 subnets

C 3.3.3.3 is directly connected, Loopback0

22.0.0.0/32 is subnetted, 1 subnets

O 22.22.22.22 [110/65] via 10.1.1.1, 00:31:25, Serial0/1

10.0.0.0/24 is subnetted, 1 subnets

C 10.1.1.0 is directly connected, Serial0/1

11.0.0.0/32 is subnetted, 1 subnets

B 11.11.11.11 [200/0] via 2.2.2.2, 00:01:40

R3(config-router)#

验证在R1上ping 3.3.3.3结果

R1#ping 3.3.3.3

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 3.3.3.3, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 40/44/60 ms

R1#