2. DDR（dial-on-demand routing）实例此例通过Cisco 2500系列路由器的aux端口实现异步拨号DDR连接。Router1拨号连接到Router2。其中采用PPP/CHAP做安全认证，在 Router1中应建立一个用户，以对端路由器主机名作为用户名，即用户名应为Router2。同时在Router2中应建立一个用户，以对端路由器主机名作为用户名，即用户名应为Router1。所建的这两用户的password必须相同。相关命令如下：任务 命令设置路由器与modem的接口指令 chat-s cript s cript-name EXPECT SEND EXPECT SEND (etc.)设置端口在挂断前的等待时间 dialer idle-timeout seconds设置协议地址与电话号码的映射 dialer map protocol next-hop-address [name hostname] [broadcast] [modem-s cript modem-regexp] [system-s cript system-regexp] [dial-string]设置电话号码 dialer string dial-string指定在特定线路下路由器默认 使用的chat-s cript s cript {dialer|reset} s cript-nameRouter1:hostname Router1!enable secret 5 $1$QKI7$wXjpFqC74vDAyKBUMallw/!username Router2 password ciscochat-s cript cisco-default "" "AT" TIMEOUT 30 OK "ATDT \T" TIMEOUT 30 CONNECT \c!interface Ethernet0ip address 10.0.0.1 255.255.255.0!interface Async1ip address 192.200.10.1 255.255.255.0encapsulation pppasync default routingasync mode dedicateddialer in-banddialer idle-timeout 60dialer map ip 192.200.10.2 name Router2 modem-s cript cisco-default 573dialer-group 1ppp authentication chap!ip route 10.0.1.0 255.255.255.0 192.200.10.2dialer-list 1 protocol ip permit!line con 0line aux 0modem InOutmodem autoconfigure discoveryflowcontrol hardware Router2:hostname Router2!enable secret 5 $1$F6EV$5U8puzNt2/o9g.t56PXHo.!username Router1 password cisco!interface Ethernet0ip address 10.0.1.1 255.255.255.0!interface Async1ip address 192.200.10.2 255.255.255.0encapsulation pppasync default routingasync mode dedicateddialer in-banddialer idle-timeout 60dialer map ip 192.200.10.1 name Router1dialer-group 1ppp authentication chap!ip route 10.0.0.0 255.255.255.0 192.200.10.1dialer-list 1 protocol ip permit!line con 0line aux 0modem InOutmodem autoconfigure discoveryflowcontrol hardware!相关调试命令：debug dialerdebug ppp authenticationdebug ppp errordebug ppp negotiationdebug ppp packetshow dialer3. 异步拨号备份DDN专线：此例主连接采用DDN专线，备份线路为电话拨号。当DDN专线连接正常时，主端口S0状态为up，line protocol亦为up,则备份线路状态为standby，line protocol为down，此时所有通信均通过主接口进行。当主接口连接发生故障时，端口状态为down，则xx备份接口，完成数据通信。此方法不适合为X.25做备份。因为，配置封装为X.25的接口只要和X.25交换机之间的连接正常其接口及line protocol的状态亦为 up,它并不考虑其它地方需与之通信的路由器的状态如何，所以若本地路由器状态正常，而对方路由器连接即使发生故障，本地也不会xx备份线路。例4将会描述如何为X.25做拨号备份。以下是相关命令：任务 命令指定主线路改变后，次线路状态发生改变的延迟时间 backup delay {enable-delay | never} {disable-delay | never}指定一个接口作为备份接口 backup interface type numberhostname c2522rb!enable secret 5 $1$J5vn$ceYDe2FwPhrZi6qsIIz6g0enable password cisco!username c4700 password 0 ciscoip subnet-zerochat-s cript cisco-default "" "AT" TIMEOUT 30 OK "ATDT \T" TIMEOUT 30 CONNECT \cchat-s cript reset atz!interface Ethernet0ip address 16.122.51.254 255.255.255.0no ip mroute-cache!interface Serial0backup delay 10 10backup interface Serial2ip address 16.250.123.18 255.255.255.252no ip mroute-cacheno fair-queue!interface Serial1no ip addressno ip mroute-cacheshutdown!interface Serial2physical-layer asyncip address 16.249.123.18 255.255.255.252encapsulation pppasync mode dedicateddialer in-banddialer idle-timeout 60dialer map ip 16.249.123.17 name c4700 6825179dialer-group 1ppp authentication chap!interface Serial3no ip addressshutdownno cdp enable!interface Serial4no ip addressshutdownno cdp enable!interface Serial5no ip addressno ip mroute-cacheshutdown!interface Serial6no ip addressno ip mroute-cacheshutdown!interface Serial7no ip addressno ip mroute-cacheshutdown!interface Serial8no ip addressno ip mroute-cacheshutdown!interface Serial9no ip addressno ip mroute-cacheshutdown!interface BRI0no ip addressno ip mroute-cacheshutdown!router eigrp 200network 16.0.0.0!ip classless!dialer-list 1 protocol ip permit!line con 0line 2s cript dialer cisco-defaults cript reset resetmodem InOutmodem autoconfigure discoveryrxspeed 38400txspeed 38400flowcontrol hardwareline aux 0line vty 0 4password ciscologin!endc2522rb#4. 异步拨号备份X.25:设置X.25的拨号备份,首先X.25连接的端口必须运行动态路由协议,异步拨号口必须使用静态路由.本例选择EIGRP作为路由选择协议,将静态路由的 Metric的值设置为200,由于EIGRP的默认Metric为90,所以当同时有两条路径通往同一网段时,其中Metric值小的路径生效,而当 X.25连接出现问题时,路由器无法通过路由协议学习到路由表，则此时静态路由生效，访问通过拨号端口实现。当X.25连接恢复正常时，路由器又可以学习到路由表，则由于 Metric值的不同，静态路由自动被动态路由所代替，这样就实现了备份的功能。路由器Router1配置如下:hostname router1!enable secret 5 $1$UTvD$99YiY2XsRMxHudcYeHn.Y.enable password cisco!username router2 password ciscoip subnet-zerochat-s cript cisco-default "" "AT" TIMEOUT 30 OK "ATDT \T" TIMEOUT 30 CONNECT \cchat-s cript reset atzinterface Ethernet0ip address 202.96.38.100 255.255.255.0!interface Serial0ip address 202.96.0.1 255.255.255.0encapsulation x25x25 address 10112227x25 htc 16x25 map ip 202.96.0.2 10112225 broadcast!interface Serial1no ip addressshutdown!!interface Async 1ip address 202.96.1.1 255.255.255.252encapsulation pppdialer in-banddialer idle-timeout 60dialer map ip 202.96.1.2 name router2 modem-s cript cisco-default 2113470dialer-group 1ppp authentication chap!router eigrp 200redistribute connectednetwork 202.96.0.0!ip route 202.96.37.0 255.255.255.0 202.96.1.2 200dialer-list 1 protocol ip permitline con 0line aux 0s cript dialer cisco-defaults cript reset resetmodem InOutmodem autoconfigure discoverytransport input allrxspeed 38400txspeed 38400flowcontrol hardwareline vty 0 4password ciscologin!end路由器Router2配置如下:hostname router2!enable secret 5 $1$T4IU$2cIqak8f/E4Ug6dLT0k.J0enable password cisco!username router1 password ciscoip subnet-zerochat-s cript cisco-default "" "AT" TIMEOUT 30 OK "ATDT \T" TIMEOUT 30 CONNECT \cchat-s cript reset atz!interface Ethernet0ip address 202.96.37.100 255.255.255.0!interface Serial0ip address 202.96.0.2 255.255.255.0no ip mroute-cacheencapsulation x25x25 address 10112225x25 htc 16x25 map ip 202.96.0.1 10112227 broadcast!interface Serial1no ip addressshutdown!interface Async1ip address 202.96.1.2 255.255.255.252encapsulation pppkeepalive 30async default routingasync mode dedicateddialer in-banddialer idle-timeout 60dialer wait-for-carrier-time 120dialer map ip 202.96.1.1 name router1 modem-s cript cisco-default 2113469dialer-group 1ppp authentication chap!router eigrp 200redistribute staticnetwork 202.96.0.0!no ip classlessip route 202.96.38.0 255.255.255.0 202.96.1.1 200dialer-list 1 protocol ip permit!line con 0exec-timeout 0 0line aux 0s cript reset resetmodem InOutmodem autoconfigure discoverytransport input allrxspeed 38400txspeed 38400flowcontrol hardwareline vty 0 4password ciscologin!end第三章 路由协议设置一、RIP协议　RIP(Routing information Protocol)是应用较早、使用较普遍的内部网关协议(Interior Gateway Protocol,简称IGP)，适用于小型同类网络，是典型的距离向量(distance-vector)协议。文档见RFC1058、 RFC1723。RIP通过广播UDP报文来交换路由信息，每30秒发送一次路由信息更新。RIP提供跳跃计数(hop count)作为尺度来衡量路由距离，跳跃计数是一个包到达目标所必须经过的路由器的数目。如果到相同目标有二个不等速或不同带宽的路由器，但跳跃计数相同，则RIP认为两个路由是等距离的。RIP最多支持的跳数为15，即在源和目的网间所要经过的最多路由器的数目为15，跳数16表示不可达。1. 有关命令任务 命令指定使用RIP协议 router rip指定RIP版本 version {1|2}1指定与该路由器相连的网络 network network注：1.Cisco的RIP版本2支持验证、密钥管理、路由汇总、无类域间路由(CIDR)和变长子网掩码(VLSMs)2. 举例Router1:router ripversion 2network 192.200.10.0network 192.20.10.0！相关调试命令：show ip protocolshow ip route