© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-1

© 2002, Cisco Systems, Inc. All rights reserved. 2 帧中继 By 梁广民

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-3 教学目标（ Objectives ） 1. 帧中继（ Frame Relay ） 2. 帧中继术语（ Frame Relay Terminology ） *3. 帧中继地址映射 （ Frame Relay Address Mapping ） **4.LMI 操作（ LMI Operation ） 5. 帧中继反向 ARP （ Frame Relay Inverse ARP ） ** 6. 配置基本的帧中继 （ Configuring Basic Frame Relay ）

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-4 Why need Frame-relay? 路由器上需要多个串口，几条 DDN 线路，就需要 几个串口 DDN 线路

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-5 Why need Frame-relay? 路由器上只需要一个串口，可以有多条 PVC 。 当帧中继网络空闲时，可以实现突发量传输。 Frame Relay 网络

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-6 帧中继预览 Frame Relay Overview 帧中继用虚电路为面向连接的服务建立连接 Virtual circuits make connections for Connection- oriented service 帧中继工作在这里 Frame Relay works here. DCE or Frame Relay Switch CSU/DSU

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-7 帧中继协议族 Frame Relay Stack OSI Reference Model Frame Relay Physical Presentation Session Transport Network Data Link Application EIA/TIA-232, EIA/TIA-449, V.35, X.21, EIA/TIA-530 Frame Relay IP/IPX/AppleTalk, etc. 帧中继工作在 OSI 参考模型的物理层和数据链路层

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-8 帧中继术语 Frame Relay Terminology Local Access Loop=T1 Local Access Loop=64 kbps DLCI: 400 PVC DLCI: 500 LMI 100=Active 400=Active DLCI: 200 DLCI: 100 PVC

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-9 Frame-relay 的关键： DLCI 1. 通俗地讲： DLCI 可以看成用来表示哪一条 PVC 。 2. 实际上它是数据链路层地址。

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-10 What is DLCI? Frame Relay 网络 R1 R2 R3 R R1 要发送数据到 R2 ，只要往 DLCI 为 102 的 PVC 上发送数据，也就是帧中的 DLCI 为 102 即可。

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-11 帧中继的帧格式 帧中继的头部

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-12 帧中继交换网络：如何实现 PVC? S0 S1 R1 R S0 ： IN 102S1:OUT201 S1 ： IN 201S0:OUT102

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-13 帧中继术语 Frame Relay Terminology 1. 访问速率（ Access rate ）：连接本地环到帧 中继的端口速度。 2. 数据链路连接标识（ DLCI ）：在源和目的设备 之间标识逻辑电路的一个数值。 3. 本地管理接口（ LMI ）；是客户前端设备和帧 中继交换机之间的信令标准，负责管理设备之间 的连接、维护设备之间的连接状态。 4. 承诺信息速率（ CIR ）： ISP 提供的有保障的速 率。

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-14 帧中继术语 Frame Relay Terminology 5. 前向显示拥塞通知（ FECN ）：当网络发生拥 塞的时候，向目的设备发送一个 FECN 数据包， 来通知拥塞。 6. 后向显示拥塞通知（ BECN ）：当网络发生拥 塞的时候，向源路由器发送一个 BECN 数据包， 来通知拥塞。同时按 25% 的比例降低数据报发送 速率。 7. 允许丢弃指示器（ DE ）：当路由器检测到拥塞 时，帧中继交换机将会首先丢弃那些 DE 位设置 为 1 的数据包。

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-15 CSU/DSU 帧中继地址映射 Frame Relay Address Mapping 从 ISP 获得本地意义的 DLCI 号码 Get locally significant DLCIs from provider 把网络地址映射到 DLCI Map your network addresses to DLCIs DLCI: 500 PVC Inverse ARP or Frame Relay map IP ( ) Frame Relay DLCI (500)

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-16 LMI 类型 LMI TYPES Cisco supports three LMI standards: Cisco （默认） ANSI Q 以后的版本不用指定 LMI 类型，可以自动适应 DLCI: 400 PVC Keepalive CSU/DSU DLCI: 500 PVC x LMI 500=Active 400=Inactive

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-17 帧中继反向 ARP Frame Relay Inverse ARP Frame Relay Cloud 1 DLCI=100DLCI=

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-18 帧中继反向 ARP Frame Relay Inverse ARP 2 Status Inquiry 2 Frame Relay Cloud 1 DLCI=100DLCI=

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-19 帧中继反向 ARP Frame Relay Inverse ARP 3 Local DLCI 100=Active 4 Local DLCI 400=Active 2 Status Inquiry 2 Frame Relay Cloud 1 DLCI=100DLCI=

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-20 帧中继反向 ARP Frame Relay Inverse ARP 4 Hello, I am Local DLCI 100=Active 4 Local DLCI 400=Active 2 Status Inquiry 2 Frame Relay Cloud 1 DLCI=100DLCI=

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-21 帧中继反向 ARP Frame Relay Inverse ARP Hello, I am Frame Relay Map DLCI 400 Active Frame Relay Cloud DLCI=100 DLCI=400 Frame Relay Map DLCI 100 Active

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-22 帧中继反向 ARP Frame Relay Inverse ARP Hello, I am Frame Relay Map DLCI 400 Active Frame Relay Cloud DLCI=100 DLCI=400 Frame Relay Map DLCI 100 Active 5 Hello, I am

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-23 帧中继反向 ARP Frame Relay Inverse ARP Keepalives Hello, I am Frame Relay Map DLCI 400 Active Frame Relay Cloud DLCI=100 DLCI=400 Frame Relay Map DLCI 100 Active 5 Hello, I am

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-24 Rel RouterRel Router interface Serial10/1 ip address encapsulation frame-relay bandwidth 64 frame-relay lmi-type cisco interface Serial1 ip address encapsulation frame-relay bandwidth 64 frame-relay lmi-type cisco HQ Branch 配置基本的帧中继 Configuring Basic Frame Relay

© 2002, Cisco Systems, Inc. All rights reserved. 25 帧中继实验 1 动态映射

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0— R1 R2 R3 R S0/0 S0/1 S0/2

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-27 要求 1. 在 R2 （模拟帧中继交换机）配置 PVC ，配置 由教师拷贝给学生 2. 在 R1/R3/R4 上，配置帧中继封装，互相 ping 通对方的串口即可。

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-28 R1/R3/R4 上的配置 int s0/X no shut clock rate encap frame-relay ip address X show frame map ：查看 IP 到 DLCI 的映射

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-29 R2 上的配置 由教师拷贝给学生

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-30

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-31 DLCI=110 IP address= /24 p1r1 DLCI=100 IP address= /24 interface Serial1 ip address encapsulation frame-relay bandwidth 64 frame-relay map ip broadcast HQ Branch Configuring a Static Frame Relay Map

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-32 Verifying Frame Relay Operation Displays line, protocol, DLCI, and LMI information Router#show interface s0/0 Serial0 is up, line protocol is up Hardware is HD64570 Internet address is /24 MTU 1500 bytes, BW 1544 Kbit, DLY usec, rely 255/255, load 1/255 Encapsulation FRAME-RELAY, loopback not set, keepalive set (10 sec) LMI enq sent 19, LMI stat recvd 20, LMI upd recvd 0, DTE LMI up LMI enq recvd 0, LMI stat sent 0, LMI upd sent 0 LMI DLCI 1023 LMI type is CISCO frame relay DTE FR SVC disabled, LAPF state down Broadcast queue 0/64, broadcasts sent/dropped 8/0, interface broadcasts 5 Last input 00:00:02, output 00:00:02, output hang never Last clearing of "show interface" counters never Queueing strategy: fifo Output queue 0/40, 0 drops; input queue 0/75, 0 drops

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-33 Displays LMI information Router#show frame-relay lmi LMI Statistics for interface Serial0 (Frame Relay DTE) LMI TYPE = CISCO Invalid Unnumbered info 0 Invalid Prot Disc 0 Invalid dummy Call Ref 0 Invalid Msg Type 0 Invalid Status Message 0 Invalid Lock Shift 0 Invalid Information ID 0 Invalid Report IE Len 0 Invalid Report Request 0 Invalid Keep IE Len 0 Num Status Enq. Sent Num Status msgs Rcvd Num Update Status Rcvd 0 Num Status Timeouts 0 Verifying Frame Relay Operation (cont.)

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-34 Displays PVC traffic statistics Verifying Frame Relay Operation (cont.) Router#show frame-relay pvc 100 PVC Statistics for interface Serial0 (Frame Relay DTE) DLCI = 100, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial0 input pkts 28 output pkts 10 in bytes 8398 out bytes 1198 dropped pkts 0 in FECN pkts 0 in BECN pkts 0 out FECN pkts 0 out BECN pkts 0 in DE pkts 0 out DE pkts 0 out bcast pkts 10 out bcast bytes 1198 pvc create time 00:03:46, last time pvc status changed 00:03:47

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-35 Displays the route maps, either static or dynamic Router#show frame-relay map Serial0 (up): ip dlci 100(0x64,0x1840), dynamic, broadcast,, status defined, active Verifying Frame Relay Operation (cont.)

© 2002, Cisco Systems, Inc. All rights reserved. 36 帧中继实验 2 静态映射及在 FR 上运行路由协议

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0— R1 R2 R3 R S0/0 S0/1 S0/2

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-38 要求 1. 在 R2 （模拟帧中继交换机）配置 PVC ，配置 由教师拷贝给学生； 2. 在 R1/R3/R4 上，配置帧中继封装，从环回口 ping 通环回口； 3. 注意： R3 和 R4 之间没有 PVC 的存在。

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-39 R1 上的配置 int s0/0 no shut clock rate encap frame-relay ip address no frame inverse-arp frame map ip broadcast frame map ip broadcast show frame map ：查看 IP 到 DLCI 的映射

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-40 R3 上的配置 int s0/1 no shut clock rate encap frame-relay ip address no frame inverse-arp frame map ip broadcast show frame map ：查看 IP 到 DLCI 的映射

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-41 R4 上的配置 int s0/1 no shut clock rate encap frame-relay ip address no frame inverse-arp frame map ip broadcast show frame map ：查看 IP 到 DLCI 的映射

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-42 R1 的 RIP 配置 int loo0 ip add router rip network network show ip route

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-43 R3 的 RIP 配置 int loo0 ip add router rip network network show ip route

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-44 R4 的 RIP 配置 int loo0 ip add router rip network network show ip route ，注意查看下一跳的 IP 地址

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-45 在 R1 上： ip split-horizon R1/R3/R4:show ip route 再注意路由的变化

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-46

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-47 问题：广播流量必须被发送到每一条 PVC Problem: Broadcast traffic must be replicated for each pvc Routing Update A C B 路由更新的可达性问题 （ Reachability Issues with Routing Updates ） B C D A

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-48 解决可达性问题 （ Resolving Reachability Issues ） 方案（ Solution ） : 在 NBMA 环境下，存在水平分割的问题 Split horizon can cause problems in NBMA environments 子接口可以解决水平分割的问题 Subinterfaces can resolve split horizon issues 一个单一的物理接口模拟多个逻辑接口 A single physical interface simulates multiple logical interfaces Subnet A Subnet B Subnet C S0 Physical Interface S0.1 S0.2 S0.3 Logical Interface

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-49 配置子接口（ Configuring Subinterfaces ） 点到点（ Point-to-Point ） – 子接口充当专线 –Subinterfaces act as leased line – 每一个子接口有自己的子网 –Each point-to-point subinterface requires its own subnet – 应用在 hub and spoke 拓扑中 –Applicable to hub and spoke topologies

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-50 配置子接口（ Configuring Subinterfaces ） 多点（ Multipoint ） – 向 NBMA 网络一样，不能解决水平分割的问题 –Subinterfaces act as NBMA network so they do not resolve the split horizon issue – 使用同一子网，可以节省地址空间 –Can save address space because uses single subnet – 应用在 partial-mesh 和 full-mesh 拓扑中 –Applicable to partial-mesh and full-mesh topology

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-51 A s0.2 B 配置点到点子接口实例 （ Configuring Point-to-Point Subinterfaces Example ） interface Serial0 no ip address encapsulation frame-relay ! interface Serial0.2 point-to-point ip address bandwidth 64 frame-relay interface-dlci 110 ! interface Serial0.3 point-to-point ip address bandwidth 64 frame-relay interface-dlci 120 ! s C DLCI=110 DLCI=12 0

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-52 interface Serial2 no ip address encapsulation frame-relay ! multipoint interface Serial2.2 multipoint ip address bandwidth 64 frame-relay map ip broadcast frame-relay map ip broadcast frame-relay map ip broadcast s2.1= /24 s2.2= /24 s2.1= /24 s2.1= /24 RTR1 B RTR3 RTR4 配置多点子接口实例 （ Multipoint Subinterfaces Configuration Example ） DLCI=120 DLCI=130 DLCI=140

© 2002, Cisco Systems, Inc. All rights reserved. 53 帧中继实验 3 点到点子接口

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0— R1 R2 R3 R S0/0 S0/1 S0/ / / / /8

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-55 要求 1. 在 R2 （模拟帧中继交换机）配置 PVC ，配置 有教师拷贝给学生； 2. 在 R1/R3/R4 上，配置帧中继封装，从环回口 ping 通环回口。

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-56 R1 上的配置 int s0/0 no shut clock rate encap frame-relay no ip address no frame inverse-arp int s0/0.3 point-to-point ip address frame interface-dlci 103 int s0/0.4 point-to-point ip address frame interface-dlci 104

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-57 R3 上的配置 int s0/1 no shut clock rate encap frame-relay no ip address no frame inverse-arp int s0/1.1 point-to-point ip address frame interface-dlci 301

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-58 R4 上的配置 int s0/1 no shut clock rate encap frame-relay no ip address no frame inverse-arp int s0/1.1 point-to-point ip address frame interface-dlci 401

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-59 R1 的 RIP 配置 int loo0 ip add router rip network network network show ip route

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-60 R3 的 RIP 配置 int loo0 ip add router rip network network show ip route

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-61 R4 的 RIP 配置 int loo0 ip add router rip network network show ip route

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-62

© 2002, Cisco Systems, Inc. All rights reserved. ICND 2.0—0-63 思考题 什么是帧中继？ 什么是 DLCI ？它是局部意义还是全局意义？ LMI 有几种类型？ FECN 和 BECN 的区别是什么？ 如何查看帧中继 PVC 的状态？ 如何建立一条帧中继的交换记录？