一、幀中繼（Frame-Relay)是一種WAN連接技術；工作在OSI模型的第二層（數據鏈接層），是一種二層封裝技術，並且是一種面向連接的服務；通過VC實現兩個分支站點的遠程互連。
FR於1990年首次被標準化。現已經取代X.25技術，它簡化了第2層的功能，只提供基本的錯誤檢測功能，提高了網絡對信息的處理效率（由於廣域網鏈路可靠性大大提高，不需要再像X.25那種結構效率太低）。
在利用幀中繼做遠程互連時，用戶首先需要將自已的設備與ISP的設備連起來，在這個連接過程中，要用到以下三種設備。
1、用戶前端設備(CPE)也叫CSU/DSU。用戶本地路由器所用的信令與電信的局端設備所用的信令是不一樣，CSU/DSU充當翻譯作用。
2、數據終端設備(DTE)也就是用戶自已的路由器。
3、數據通信設備(DCE)也就是電信的局端設備。
二、FR連接運行在虛電路（VC）上，每條VC都由一個數據鏈路連接標識符（DLCI）標識。並將此DLCI映射到一個IP地址。DLCI號在幀中繼中相當於二層地址。
VC分爲：永久虛電路（PVC）、交換虛電路（SVC）。
PVC：需要不斷通過FR在DTE之間傳輸數據時使用。
SVC：用於間歇性的通過FR在DTE之間傳輸數據。要考慮ISP是否支持。
FR交換機將2臺路由器的DLCI關聯起來，從而創建1條PVC。
DLCI只具有本地意義。
DLCI的範圍（16－1007）
0－15和1008－1023被保留
1019和1020保留用於廣播
1023保留用於Cisco LMI
0保留用於LMI類型的ANSI和Q.933A
DLCI地址映射：
要通過FR傳輸數據，必須將本地DLCI和目的IP地址關聯。
地址映射可手工配置，也可動態生成。
動態生成時使用幀中繼反向地址解析協議（IARP）。
本地管理接口（LMI）
LMI是指路由器與電信的局端FR交換機之間通信的協議，負責管理設備之間的連接以及維護連接狀態。
LMI是可以配置的，但路由器嘗試自動檢測FR交換機使用的LMI類型。
LMI的三種類型：Cisco/ANSI/Q933A
FR網絡是非廣播多路訪問（NBMA）網絡。
三、幀中繼(Frame-relay)之全網互連的配置
1、拓樸圖如下：
2、R5模擬成幀中繼交換機，按如下步驟配置
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FR5(config)#no ip routing #關閉路由功能
FR5(config)#frame-relay switching #將R5配置成幀中繼交換機
FR5(config)#int s1/1
FR5(config-if)#encapsulation frame-relay ?
MFR Multilink Frame Relay bundle interface
ietf Use RFC1490/RFC2427 encapsulation
<cr>
FR5(config-if)#encapsulation frame-relay #默認是Cisco封裝類型，如果連接的是Cisco路由器，建議使用這種封裝，如果連接是非Cisco路由器，則選擇ietf。
FR5(config-if)#clock rate 64000 #在接口上配置時鐘頻率
FR5(config-if)#frame-relay lmi-type cisco #指定接口LMI的類型[cisco|ansi|q933a]
FR5(config-if)#frame-relay intf-type dce #將接口指定爲DCE接口
FR5(config-if)#frame-relay route 102 int s1/2 201 #寫幀中繼到R2的路由，實際上就是建立PVC；frame-relay route + 入接口DLCI號 + 出接口 + 出接口的DLCI號
FR5(config-if)#frame-relay route 103 int s1/3 301 #寫幀中繼到R3的路由
FR5(config-if)#frame-relay route 104 int s1/4 401 #寫幀中繼到R4的路由
FR5(config-if)#no shut #激活接口
FR5(config-if)#exit
FR5(config)#int s1/2
FR5(config-if)#encapsulation frame-relay
FR5(config-if)#clock rate 64000
FR5(config-if)#frame-relay lmi-type cisco
FR5(config-if)#frame-relay intf-type dce
FR5(config-if)#frame-relay route 201 int s1/1 102
FR5(config-if)#frame-relay route 203 int s1/3 302
FR5(config-if)#frame-relay route 204 int s1/4 402
FR5(config-if)#no shut
FR5(config-if)#exit
FR5(config)#int s1/3
FR5(config-if)#encapsulation frame
FR5(config-if)#clock rate 64000
FR5(config-if)#frame-relay intf-type dce
FR5(config-if)#frame-relay lmi-type cisco
FR5(config-if)#frame-relay route 301 int s1/1 103
FR5(config-if)#frame-relay route 304 int s1/4 403
FR5(config-if)#frame-relay route 302 int s1/2 203
FR5(config-if)#no shutdown
FR5(config-if)#exit
FR5(config)#int s1/4
FR5(config-if)#encapsulation frame-relay
FR5(config-if)#clock rate 64000
FR5(config-if)#frame-relay lmi-type cisco
FR5(config-if)#frame-relay intf-type dce
FR5(config-if)#frame-relay route 402 int s1/2 204
FR5(config-if)#frame-relay route 403 int s1/3 304
FR5(config-if)#frame-relay route 401 int s1/1 104
FR5(config-if)#no shut
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到此，FR5幀中繼交換機就模擬好了！
3、北京總部R1路由器的配置
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R1(config)#int s1/1
R1(config-if)#ip add 12.0.0.1 255.255.255.0 #配置IP
R1(config-if)#encapsulation frame-relay #封裝幀中繼
R1(config-if)#no shut #激活接口
R1(config-if)#exit
R1(config)#int loopback 0 #迴環接口用於模擬內網測試
R1(config-if)#ip add 1.1.1.1 255.255.255.255
用ping去測試網絡的連通性
R1(config-if)#do ping 12.0.0.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 12.0.0.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 60/88/144 ms
R1(config-if)#do ping 12.0.0.3
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 12.0.0.3, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 64/96/140 ms
R1(config-if)#do ping 12.0.0.4
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 12.0.0.4, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 64/104/180 ms
R1(config-if)#do ping 12.0.0.1 #R1不能夠ping通自己，通過show frame-relay map 可看到沒有指向自己的Map
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 12.0.0.1, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
R1(config-if)#do show frame-relay map #查看frame-relay map
Serial1/1 (up): ip 12.0.0.2 dlci 102(0x66,0x1860), dynamic,
broadcast,, status defined, active
Serial1/1 (up): ip 12.0.0.3 dlci 103(0x67,0x1870), dynamic,
broadcast,, status defined, active
Serial1/1 (up): ip 12.0.0.4 dlci 104(0x68,0x1880), dynamic,
broadcast,, status defined, active
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4、上海分部R2路由器的配置
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R2(config)#int s1/2
R2(config-if)#encapsulation frame-relay #封裝幀中繼
R2(config-if)#ip add 12.0.0.2 255.255.255.0 #配置IP
R2(config-if)#no shut #激活接口
R2(config-if)#exit
R2(config)#int lo 0 #迴環接口用於模擬內網測試
R2(config-if)#ip add 2.2.2.2 2
R2(config-if)#ip add 2.2.2.2 255.255.255.255
R2(config-if)#do ping 12.0.0.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 12.0.0.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 64/79/108 ms
R2(config-if)#do ping 12.0.0.3
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 12.0.0.3, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 60/88/112 ms
R2(config-if)#do ping 12.0.0.4
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 12.0.0.4, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 44/76/120 ms
R2(config-if)#do ping 12.0.0.2 #R2不能夠ping通自己，沒有指向自己的Map
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 12.0.0.2, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
R2(config-if)#do show frame-relay map #查看frame-relay map
Serial1/2 (up): ip 12.0.0.1 dlci 201(0xC9,0x3090), dynamic,
broadcast,, status defined, active
Serial1/2 (up): ip 12.0.0.3 dlci 203(0xCB,0x30B0), dynamic,
broadcast,, status defined, active
Serial1/2 (up): ip 12.0.0.4 dlci 204(0xCC,0x30C0), dynamic,
broadcast,, status defined, active
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5、深圳分部R3路由器的配置
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R3(config)#int s1/3
R3(config-if)#encapsulation frame-relay
R3(config-if)#ip add 12.0.0.3 255.255.255.0
R3(config-if)#no shut
R3(config-if)#exit
R3(config)#int lo 0
R3(config-if)#ip add 3.3.3.3 255.255.255.255
R3(config-if)#do ping 12.0.0.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 12.0.0.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 24/68/104 ms
R3(config-if)#do ping 12.0.0.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 12.0.0.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 56/88/148 ms
R3(config-if)#do ping 12.0.0.4
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 12.0.0.4, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 48/73/108 ms
R3(config-if)#do ping 12.0.0.3 #R3不能夠ping通自己，沒有指向自己的Map
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 12.0.0.3, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
R3(config-if)#do show frame-relay map #查看frame-relay map
Serial1/3 (up): ip 12.0.0.1 dlci 301(0x12D,0x48D0), dynamic,
broadcast,, status defined, active
Serial1/3 (up): ip 12.0.0.2 dlci 302(0x12E,0x48E0), dynamic,
broadcast,, status defined, active
Serial1/3 (up): ip 12.0.0.4 dlci 304(0x130,0x4C00), dynamic,
broadcast,, status defined, active
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6、廣州分部R4路由器的配置
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R4(config)#int s1/4
R4(config-if)#encapsulation frame-relay
R4(config-if)#ip add 12.0.0.4 255.255.255.0
R4(config-if)#no shutdown
R4(config-if)#exit
R4(config)#int lo 0
R4(config-if)#ip add 4.4.4.4 255.255.255.255
R4(config-if)#do ping 12.0.0.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 12.0.0.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 64/76/100 ms
R4(config-if)#do ping 12.0.0.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 12.0.0.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 44/89/140 ms
R4(config-if)#do ping 12.0.0.3
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 12.0.0.3, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 60/96/172 ms
R4(config-if)#do ping 12.0.0.4 #R4不能夠ping通自己，沒有指向自己的Map
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 12.0.0.4, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
R4#show frame-relay map #查看frame-relay map
Serial1/4 (up): ip 12.0.0.1 dlci 401(0x191,0x6410), dynamic,
broadcast,, status defined, active
Serial1/4 (up): ip 12.0.0.2 dlci 402(0x192,0x6420), dynamic,
broadcast,, status defined, active
Serial1/4 (up): ip 12.0.0.3 dlci 403(0x193,0x6430), dynamic,
broadcast,, status defined, active
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通過show frame-relay map 可看到在R1、R2、R3、R4上所見到的幀中繼MAP都是Inverse-ARP動態(dynamic)映射過來的，並且都支持廣播；還有就是他們上面都沒有自己的map，所以不能ping通自己。
四、實際應用中通常都是手動映射的（配置靜態幀中繼）
1、R1上手動映射幀中繼MAP
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R1(config)#int s1/1
R1(config-if)#no frame-relay inverse-arp #關閉幀中繼的逆向ARP，不允許動態映射
R1(config-if)#do clear frame-relay inarp #清除逆向ARP留下的cache
R2(config-if)#do show frame-relay map #已清空ARP留下的緩存
R1(config-if)#frame-relay map ip 12.0.0.2 102 broadcast #將IP地址靜態映射到DLCI，加broadcast參數實現僞廣播；frame-relay map ip +目的IP + 本地DLCI號 +模擬廣播
R1(config-if)#frame-relay map ip 12.0.0.3 103 broadcast #同上
R1(config-if)#frame-relay map ip 12.0.0.4 104 broadcast #同上
R1(config-if)#frame-relay map ip 12.0.0.1 102 broadcast #指向自己的Map,此處的DLCI號也可以是103，104
用ping 測試網絡的連通性
R1(config-if)#do ping 12.0.0.1 #可以ping 通自己了！
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 12.0.0.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 160/214/276 ms
R1(config-if)#do ping 12.0.0.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 12.0.0.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 20/52/124 ms
R1(config-if)#do ping 12.0.0.3
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 12.0.0.3, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 16/48/140 ms
R1(config-if)#do ping 12.0.0.4
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 12.0.0.4, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 20/65/140 ms
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2、R2上手動映射幀中繼MAP
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R2(config)#int s1/2
R2(config-if)#no frame-relay inverse-arp
R2(config-if)#do clear frame-relay inarp
R2(config-if)#do show frame-relay map #已清空ARP留下的緩存
R2(config-if)#frame-relay map ip 12.0.0.1 201 broadcast
R2(config-if)#frame-relay map ip 12.0.0.3 203 broadcast
R2(config-if)#frame-relay map ip 12.0.0.4 204 broadcast
R2(config-if)#frame-relay map ip 12.0.0.2 201 broadcast #此處的DLCI號也可以是203，204
R2(config-if)#do ping 12.0.0.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 12.0.0.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 20/69/140 ms
R2(config-if)#do ping 12.0.0.2 #可以ping 通自己了！
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 12.0.0.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 28/70/156 ms
R2(config-if)#do ping 12.0.0.3
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 12.0.0.3, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 12/49/136 ms
R2(config-if)#do ping 12.0.0.4
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 12.0.0.4, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 20/49/140 ms
3、R3上手動映射幀中繼MAP
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R3(config)#int s1/3
R3(config-if)#no frame-relay inverse-arp
R3(config-if)#do clear frame-relay inarp
R3(config-if)#do show frame-relay map #已清空ARP留下的緩存
R3(config-if)#frame-relay map ip 12.0.0.1 301 broadcast
R3(config-if)#frame-relay map ip 12.0.0.2 302 broadcast
R3(config-if)#frame-relay map ip 12.0.0.4 304 broadcast
R3(config-if)#frame-relay map ip 12.0.0.3 301 broadcast #此處的DLCI號也可以是303，302
R3(config-if)#do ping 12.0.0.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 12.0.0.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 20/45/112 ms
R3(config-if)#do ping 12.0.0.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 12.0.0.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 20/52/124 ms
R3(config-if)#do ping 12.0.0.3
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 12.0.0.3, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 32/77/172 ms
R3(config-if)#do ping 12.0.0.4
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 12.0.0.4, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 20/44/112 ms
4、R4上手動映射幀中繼MAP
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R4(config)#int s1/4
R4(config-if)#no frame-relay inverse-arp
R4(config-if)#do clear frame-relay inarp
R4(config-if)#do show frame-relay map #已清空ARP留下的緩存
R4(config-if)#frame-relay map ip 12.0.0.1 401 broadcast
R4(config-if)#frame-relay map ip 12.0.0.2 402 broadcast
R4(config-if)#frame-relay map ip 12.0.0.3 403 broadcast
R4(config-if)#frame-relay map ip 12.0.0.4 401 broadcast #此處的DLCI號也可以是403,402
R4(config-if)#do ping 12.0.0.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 12.0.0.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 24/58/100 ms
R4(config-if)#do ping 12.0.0.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 12.0.0.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 20/52/112 ms
R4(config-if)#do ping 12.0.0.3
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 12.0.0.3, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 20/51/144 ms
R4(config-if)#do ping 12.0.0.4
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 12.0.0.4, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 36/70/160 ms
五、在R、R2、R3和R4上運行一種路由協議，宣告接口,此處用RIPv2
1、在R1上運行RIPv2路由協議
----------------------------------------------------------------------------
R1(config)#router rip
R1(config-router)#version 2
R1(config-router)#no auto-summary
R1(config-router)#network 1.0.0.0
R1(config-router)#network 12.0.0.0
R1(config-router)#do show ip route #在R2、R3、R4都啓用了路由協議纔可查看到所有路由條目
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 not set
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
R 2.2.2.2 [120/1] via 12.0.0.2, 00:01:01, Serial1/1
3.0.0.0/32 is subnetted, 1 subnets
R 3.3.3.3 [120/1] via 12.0.0.3, 00:01:01, Serial1/1
4.0.0.0/32 is subnetted, 1 subnets
R 4.4.4.4 [120/1] via 12.0.0.4, 00:01:01, Serial1/1
12.0.0.0/24 is subnetted, 1 subnets
C 12.0.0.0 is directly connected, Serial1/1
2、在R2上運行RIPv2路由協議
----------------------------------------------------------------------------
R2(config)#router rip
R2(config-router)#version 2
R2(config-router)#no auto-summary
R2(config-router)#netowrk 2.0.0.0
R2(config-router)#network 12.0.0.0
R2(config-router)#do show ip route #在R1、R3、R4都啓用了路由協議纔可查看到所有路由條目
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 not set
1.0.0.0/32 is subnetted, 1 subnets
R 1.1.1.1 [120/1] via 12.0.0.1, 00:00:17, Serial1/2
2.0.0.0/32 is subnetted, 1 subnets
C 2.2.2.2 is directly connected, Loopback0
3.0.0.0/32 is subnetted, 1 subnets
R 3.3.3.3 [120/2] via 12.0.0.3, 00:00:17, Serial1/2
4.0.0.0/32 is subnetted, 1 subnets
R 4.4.4.4 [120/2] via 12.0.0.4, 00:00:17, Serial1/2
12.0.0.0/24 is subnetted, 1 subnets
C 12.0.0.0 is directly connected, Serial1/2
3、在R3上運行RIPv2路由協議
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R3(config)#router rip
R3(config-router)#version 2
R3(config-router)#no auto-summary
R3(config-router)#network 3.0.0.0
R3(config-router)#network 12.0.0.0
R3(config-router)#do show ip route #在R1、R2、R4都啓用了路由協議纔可查看到所有路由條目
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 not set
1.0.0.0/32 is subnetted, 1 subnets
R 1.1.1.1 [120/1] via 12.0.0.1, 00:00:20, Serial1/3
2.0.0.0/32 is subnetted, 1 subnets
R 2.2.2.2 [120/2] via 12.0.0.2, 00:00:20, Serial1/3
3.0.0.0/32 is subnetted, 1 subnets
C 3.3.3.3 is directly connected, Loopback0
4.0.0.0/32 is subnetted, 1 subnets
R 4.4.4.4 [120/2] via 12.0.0.4, 00:00:21, Serial1/3
12.0.0.0/24 is subnetted, 1 subnets
C 12.0.0.0 is directly connected, Serial1/3
4、在R4上運行RIPv2路由協議
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R4(config)#router rip
R4(config-router)#version 2
R4(config-router)#no auto-summary
R4(config-router)#network 4.0.0.0
R4(config-router)#network 12.0.0.0
R4(config-router)#do show ip route #在R1、R2、R3都啓用了路由協議纔可查看到所有路由條目
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 not set
1.0.0.0/32 is subnetted, 1 subnets
R 1.1.1.1 [120/1] via 12.0.0.1, 00:00:24, Serial1/4
2.0.0.0/32 is subnetted, 1 subnets
R 2.2.2.2 [120/2] via 12.0.0.2, 00:00:24, Serial1/4
3.0.0.0/32 is subnetted, 1 subnets
R 3.3.3.3 [120/2] via 12.0.0.3, 00:00:24, Serial1/4
4.0.0.0/32 is subnetted, 1 subnets
C 4.4.4.4 is directly connected, Loopback0
12.0.0.0/24 is subnetted, 1 subnets
C 12.0.0.0 is directly connected, Serial1/4
六、以上R1、R2、R3、R4之間實現了全網互連(full-mesh)，可提供最大容錯能力，不過此連接成本最爲昂貴。
可以通過實現部分連接，只對重要結點採取多鏈路互連即可，並且從安全角度考慮，如允許總部訪問各分支機構，各分支機構只能訪問總部，不能相互訪問。又或者分支機構只能通過總部再訪問其他分支機構。
1、在幀中繼交換機FR5上No掉各分支機構互連的幀中繼路由，只保留去往總部的。
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FR5(config)#int s1/2
FR5(config-if)#no frame-relay route 203 int s1/3 302
FR5(config-if)#no frame-relay route 204 int s1/4 402
FR5(config-if)#exit
FR5(config)#int s1/3
FR5(config-if)#no frame-relay route 304 int s1/4 403
FR5(config-if)#no frame-relay route 302 int s1/2 203
FR5(config-if)#exit
FR5(config)#int s1/4
FR5(config-if)#no frame-relay route 402 int s1/2 204
FR5(config-if)#no frame-relay route 403 int s1/3 304
FR5(config-if)#exit
此時，總部能與各分支機構通信，各分支機構之間已不能再通信。
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2、幀中繼交換機FR5上已沒有各分支機構間的的幀中繼路由，所以可清除各分支機構R2、R3、R4上無用的靜態映射幀中繼MAP，見如下：
清除R2上無用的靜態映射幀中繼MAP
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R2(config)#int s1/2
R2(config-if)#do clear frame-relay inarp
R2(config-if)#no frame-relay map ip 12.0.0.3 203 broadcast
R2(config-if)#no frame-relay map ip 12.0.0.4 204 broadcast
清除R3上無用的靜態映射幀中繼MAP
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R3(config)#int s1/3
R3(config-if)#no frame-relay map ip 12.0.0.2 302 broadcast
R3(config-if)#no frame-relay map ip 12.0.0.4 304 broadcast
清除R4上無用的靜態映射幀中繼MAP
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R4(config)#int s1/4
R4(config-if)#do clear frame-relay inarp
R4(config-if)#no frame-relay map ip 12.0.0.2 402 broadcast
R4(config-if)#no frame-relay map ip 12.0.0.3 403 broadcast
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3、按以下方式可讓各分支構通過總部互訪。
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R2(config)#int s1/2
R2(config-if)#frame-relay map ip 12.0.0.4 201 broadcast
R2(config-if)#frame-relay map ip 12.0.0.3 201 broadcast
R2(config-if)#do clear ip route *
R2(config)#int s1/3
R3(config-if)#frame-relay map ip 12.0.0.2 301 broadcast
R3(config-if)#frame-relay map ip 12.0.0.4 301 broadcast
R2(config-if)#frame-relay map ip 12.0.0.3 201 broadcast
R3(config-if)#do clear ip route *
R2(config)#int s1/4
R4(config-if)#frame-relay map ip 12.0.0.2 401 broadcast
R4(config-if)#frame-relay map ip 12.0.0.3 401 broadcast
R4(config-if)#do clear ip route *
測試信息就不貼上了，大家有興趣可以做做，一塊討論哈！