作者: memtec 五、ISDN 1. 综合数字业务网（ISDN） 综合数字业务网（ISDN）由数字电话和数据传输服务两部分组成，一般由电话局提供这种服务。ISDN的基本速率接口（BRI）服务提供2个B信道和1个D信道（2B+D）。BRI的B信道速率为64Kbps,用于传输用户数据。D信道的速率为16Kbps，主要传输控制信号。在北美和日本，ISDN的主速率接口（PRI）提供23个B信道和1个D信道，总速率可达1.544Mbps，其中D信道速率为64Kbps。而在欧洲、澳大利亚等国家，ISDN的PRI提供30个B信道和1个64Kbps D信道，总速率可达2.048Mbps。我国电话局所提供ISDN PRI为30B+D。 2. 基本命令 任务 命令 设置ISDN交换类型 isdn switch-type switch-type1 接口设置 interface bri 0 设置PPP封装 encapsulation ppp 设置协议地址与电话号码的映射 dialer map protocol next-hop-address [name hostname] [broadcast] [dial-string] 启动PPP多连接 ppp multilink 设置启动另一个B通道的阈值 dialer load-threshold load 显示ISDN有关信息 show isdn {active history memory services status [dsl interface-type number] timers} 注：1.交换机类型如下表,国内交换机一般为basic-net3。 按区域分要害字 交换机类型 Australia basic-ts013 Australian TS013 switches Europe basic-1tr6 German 1TR6 ISDN switches basic-nwnet3 Norway NET3 switches (phase 1) basic-net3 NET3 ISDN switches (UK, Denmark, and other nations); covers the Euro-ISDN E-DSS1 signalling system primary-net5 NET5 switches (UK and Europe) vn2 French VN2 ISDN switches vn3 French VN3 ISDN switches Japan ntt Japanese NTT ISDN switches primary-ntt Japanese ISDN PRI switches North America basic-5ess AT&T basic rate switches basic-dms100 NT DMS-100 basic rate switches basic-ni1 National ISDN-1 switches primary-4ess AT&T 4ESS switch type for the U.S. (ISDN PRI only) primary-5ess AT&T 5ESS switch type for the U.S. (ISDN PRI only) primary-dms100 NT DMS-100 switch type for the U.S. (ISDN PRI only) New Zealand basic-nznet3 New Zealand Net3 switches 3. ISDN实现DDR（dial-on-demand routing）实例: 设置如下： Router1: hostname router1 user router2 passWord cisco ! isdn switch-type basic-net3 ! interface bri 0 ip address 192.200.10.1 255.255.255.0 encapsulation ppp dialer map ip 192.200.10.2 name router2 572 dialer load-threshold 80 ppp multilink dialer-group 1 ppp authentication chap ！ dialer-list 1 protocol ip permit !
Router2: hostname router2 user router1 password cisco ! isdn switch-type basic-net3 ! interface bri 0 ip address 192.200.10.2 255.255.255.0 encapsulation ppp dialer map ip 192.200.10.1 name router1 571 dialer load-threshold 80 ppp multilink dialer-group 1 ppp authentication chap ！ dialer-list 1 protocol ip permit ! Cisco路由器同时支持回拨功能，我们将路由器Router1作为Callback Server,Router2作为Callback Client。
与回拨相关命令: 任务 命令 映射协议地址和电话号码，并在接口上使用在全局模式下定义的PPP回拨的映射类别。 dialer map protocol address name hostname class classname dial-string 设置接口支持PPP回拨 ppp callback accept 在全局模式下为PPP回拨设置映射类别 map-class dialer classname 通过查找注册在dialer map里的主机名来决定回拨. dialer callback-server [username] 设置接口要求PPP回拨 ppp callback request 设置如下： Router1: hostname router1 user router2 password cisco ! isdn switch-type basic-net3 ! interface bri 0 ip address 192.200.10.1 255.255.255.0 encapsulation ppp dialer map ip 192.200.10.2 name router2 class s3 572 dialer load-threshold 80 ppp callback accept ppp multilink dialer-group 1 ppp authentication chap ！ map-class dialer s3 dialer callback-server username dialer-list 1 protocol ip permit !
Router2: hostname router2 user router1 password cisco ! isdn switch-type basic-net3 ! interface bri 0 ip address 192.200.10.2 255.255.255.0 encapsulation ppp dialer map ip 192.200.10.1 name router1 571 dialer load-threshold 80 ppp callback request ppp multilink dialer-group 1 ppp authentication chap ！ dialer-list 1 protocol ip permit ! 相关调试命令： debug dialer debug isdn event debug isdn q921 debug isdn q931 debug ppp authentication debug ppp error debug ppp negotiation debug ppp packet show dialer show isdn status 举例:执行debug dialer命令观察router2呼叫router1,router1回拨router2的过程. router1#debug dialer router2#ping 192.200.10.1
router1# 00:03:50: %LINK-3-UPDOWN: Interface BRI0:1, changed state to up 00:03:50: BRI0:1PP callback Callback server starting to router2 572 00:03:50: BRI0:1: disconnecting call 00:03:50: %LINK-3-UPDOWN: Interface BRI0:1, changed state to down 00:03:50: BRI0:1: disconnecting call 00:03:50: BRI0:1: disconnecting call 00:03:51: %LINK-3-UPDOWN: Interface BRI0:2, changed state to up 00:03:52: callback to router2 already started 00:03:52: BRI0:2: disconnecting call 00:03:52: %LINK-3-UPDOWN: Interface BRI0:2, changed state to down 00:03:52: BRI0:2: disconnecting call 00:03:52: BRI0:2: disconnecting call 00:04:05: : Callback timer eXPired 00:04:05: BRI0:beginning callback to router2 572 00:04:05: BRI0: Attempting to dial 572 00:04:05: Freeing callback to router2 572 00:04:05: %LINK-3-UPDOWN: Interface BRI0:1, changed state to up 00:04:05: BRI0:1: No callback negotiated 00:04:05: %LINK-3-UPDOWN: Interface Virtual-access1, changed state to up 00:04:05: dialer Protocol up for Vi1 00:04:06: %LINEPROTO-5-UPDOWN: Line protocol on Interface BRI0:1, changed state to up 00:04:06: %LINEPROTO-5-UPDOWN: Line protocol on Interface Virtual-Access1, chang ed state to up 00:04:11: %ISDN-6-CONNECT: Interface BRI0:1 is now connected to 572 #router1 4. ISDN访问首都在线263网实例: 本地局部网地址为10.0.0.0/24,属于保留地址，通过NAT地址翻译功能，局域网用户可以通过ISDN上263网访问Internet。 263的ISDN电话号码为2633，用户为263，口令为263，所涉及的命令如下表： 任务 命令 指定接口通过PPP/IPCP地址协商获得IP地址 ip address negotiated 指定内部和外部端口 ip nat {inside outside} 使用ppp/pap作认证 ppp authentication pap callin 指定接口属于拨号组1 dialer-group 1 定义拨号组1答应所有IP协议 dialer-list 1 protocol ip permit 设定拨号，号码为2633 dialer string 2633 设定登录263的用户名和口令 ppp pap sent-username 263 password 263 设定默认路由 ip route 0.0.0.0 0.0.0.0 bri 0 设定符合访问列表2的所有源地址被翻译为bri 0所拥有的地址 ip nat inside source list 2 interface bri 0 overload 设定访问列表2，答应所有协议 access-list 2 permit any 具体配置如下： hostname Cisco2503 ! isdn switch-type basic-net3 ! ip subnet-zero no ip domain-lookup ip routing ! interface Ethernet 0 ip address 10.0.0.1 255.255.255.0 ip nat inside no shutdown ! interface Serial 0 shutdown no description no ip address ! interface Serial 1 shutdown no description no ip address ! interface bri 0 ip address negotiated ip nat outside encapsulation ppp ppp authentication pap callin ppp multilink dialer-group 1 dialer hold-queue 10 dialer string 2633 dialer idle-timeout 120 ppp pap sent-username 263 password 263 no cdp enable no ip split-horizon no shutdown ! ip classless ! ! Static Routes ! ip route 0.0.0.0 0.0.0.0 bri 0 ! ! Access Control List 2 ! access-list 2 permit any ! dialer-list 1 protocol ip permit ! ! Dynamic NAT ! ip nat inside source list 2 interface bri 0 overload snmp-server community public ro ! line console 0 exec-timeout 0 0 ! line vty 0 4 ! end
>set system c765 c765> set multidestination on c765> set switch net3 c765> set ppp multilink on c765> cd lan c765:LAN> set ip routing on c765:LAN> set ip address 10.0.0.1 c765:LAN> set ip netmask 255.0.0.0 c765:LAN> set briding off c765:LAN>cd c765> set user remotenet New user remotenet being created c765:remotenet> set ip routing on c765:remotenet> set bridging off c765:remotenet> set ip framing none c765:remotenet> set ppp clientname 263 c765:remotenet> set ppp password client Enter new Password: 263 Re-Type new Password: 263 c765:remotenet> set ppp authentication out none c765:remotenet> set ip address 0.0.0.0 c765:remotenet> set ip netmask 0.0.0.0 c765:remotenet> set ppp address negotiation local on c765:remotenet> set ip pat on c765:remotenet> set ip route destination 0.0.0.0/0 gateway 0.0.0.0 c765:remotenet> set number 2633 c765:remotenet> set active 命令描述如下： 任务 命令 设置路由器系统名称 set system c765 答应路由器呼叫多个目的地 set multidestination on 设置ISDN交换机类型为NET3 set switch net3 答应点到点间多条通道连接实现负载均衡 set ppp multilink on 关掉桥接 set briding off 建立用户预制文件用于设置拨号连接参数- 可以设置多个用户预制文件用于相同的物理端口对应于不同的连接。 set user remotenet 使用PPP/IPCP set ip framing none 设置上网用户帐号 set ppp clientname 263 设置上网口令 set ppp password client Enter new Password: 263 Re-Type new Password: 263 不用PPP/CHAP或PAP做认证 set ppp authentication out none 答应地址磋商 set ppp address negotiation local on 设置地址翻译 set ip pat on 设置默认路由 set ip route destination 0.0.0.0/0 gateway 0.0.0.0 设置ISP的电话号码 set number 2633 激活用户预制文件 set active 六、PSTN 电话网络(PSTN)是目前普及程度最高、成本最低的公用通讯网络，它在网络互连中也有广泛的应用。电话网络的应用一般可分为两种类型，一种是同等级别机构之间以按需拨号(DDR)的方式实现互连，一种是ISP为拨号上网为用户提供的远程访问服务的功能。 1. 远程访问 1.1.Access Server基本设置： 选用Cisco2511作为访问服务器,采用IP地址池动态分配地址.远程工作站使用WIN95拨号网络实现连接。 全局设置： 任务 命令 设置用户名和密码 username username password password 设置用户的IP地址池 ip local pool {default pool-name low-ip-address [high-ip-address]} 指定地址池的工作方式 ip address-pool [dhcp-proxy-client local] 基本接口设置命令： 任务 命令 设置封装形式为PPP encapsulation ppp 启动异步口的路由功能 async default routing 设置异步口的PPP工作方式 async mode {dedicated interactive} 设置用户的IP地址 peer default ip address {ip-address dhcp pool [pool-name]} 设置IP地址与Ethernet0相同 ip unnumbered ethernet0 line拨号线设置： 任务 命令 设置modem的工作方式 modem {inoutdialin} 自动配置modem类型 modem autoconfig discovery 设置拨号线的通讯速率 speed speed 设置通讯线路的流控方式 flowcontrol {none software [lock] [in out] hardware [in out]} 连通后自动执行命令 autocommand command 访问服务器设置如下： Router: hostname Router enable secret 5 $1$EFqU$tYLJLrynNUKzE4bx6fmH// ! interface Ethernet0 ip address 10.111.4.20 255.255.255.0 ! interface Async1 ip unnumbered Ethernet0 encapsulation ppp keepalive 10 async mode interactive peer default ip address pool Cisco2511-Group-142 ! ip local pool Cisco2511-Group-142 10.111.4.21 10.111.4.36 ! line con 0 exec-timeout 0 0 password cisco ! line 1 16 modem InOut modem autoconfigure discovery flowcontrol hardware ! line aux 0 transport input all line vty 0 4 password cisco ! end 相关调试命令： show interface show line
1.2. Access Server通过Tacacs服务器实现安全认证： 使用一台WINDOWS NT服务器作为Tacacs服务器，地址为10.111.4.2,运行Cisco2511随机带的Easy ACS 1.0软件实现用户认证功能. 相关设置： 任务 命令 激活AAA访问控制 aaa new-model 用户登录时默认起用Tacacs+做AAA认证 aaa authentication login default tacacs+ 列表名为no_tacacs使用ENABLE口令做认证 aaa authentication login no_tacacs enable 在运行PPP的串行线上采用Tacacs+做认证 aaa authentication ppp default tacacs+ 由TACACS+服务器授权运行EXEC aaa authorization exec tacacs+ 由TACACS+服务器授权与网络相关的服务请求。 aaa authorization network tacacs+ 为EXEC会话运行记帐.进程开始和结束时发通告给TACACS+服务器。 aaa accounting exec start-stop tacacs+ 为与网络相关的服务需求运行记帐包括SLIP,PPP,PPP NCPs,ARAP等.在进程开始和结束时发通告给TACACS+服务器。 aaa accounting network start-stop tacacs+ 指定Tacacs服务器地址 tacacs-server host 10.111.4.2 在Tacacs+服务器和访问服务器设定共享的要害字，访问服务器和Tacacs+服务器使用这个要害字去加密口令和响应信息。这里使用tac作为要害字。 tacacs-server key tac 访问服务器设置如下： hostname router ! aaa new-model aaa authentication login default tacacs+ aaa authentication login no_tacacs enable aaa authentication ppp default tacacs+ aaa authorization exec tacacs+ aaa authorization network tacacs+ aaa accounting exec start-stop tacacs+ aaa accounting network start-stop tacacs+ enable secret 5 $1$kN4g$CvS4d2.rJzWntCnn/0hvE0 ! interface Ethernet0 ip address 10.111.4.20 255.255.255.0 ! interface Serial0 no ip address shutdown interface Serial1 no ip address shutdown ! interface Group-Async1 ip unnumbered Ethernet0 encapsulation ppp async mode interactive peer default ip address pool Cisco2511-Group-142 no cdp enable group-range 1 16 ! ip local pool Cisco2511-Group-142 10.111.4.21 10.111.4.36 tacacs-server host 10.111.4.2 tacacs-server key tac ! line con 0 exec-timeout 0 0 password cisco login authentication no_tacacs line 1 16 login authentication tacacs modem InOut modem autoconfigure type usr_courier autocommand ppp transport input all stopbits 1 rxspeed 115200 txspeed 115200 flowcontrol hardware line aux 0 transport input all line vty 0 4 password cisco ! end
Router2: hostname Router2 ! enable secret 5 $1$F6EV$5U8puzNt2/o9g.t56PXHo. ! username Router1 password cisco ! interface Ethernet0 ip address 10.0.1.1 255.255.255.0 ! interface Async1 ip address 192.200.10.2 255.255.255.0 encapsulation ppp async default routing async mode dedicated dialer in-band dialer idle-timeout 60 dialer map ip 192.200.10.1 name Router1 dialer-group 1 ppp authentication chap ! ip route 10.0.0.0 255.255.255.0 192.200.10.1 dialer-list 1 protocol ip permit ! line con 0 line aux 0 modem InOut modem autoconfigure discovery flowcontrol hardware ! 相关调试命令： debug dialer debug ppp authentication debug ppp error debug ppp negotiation debug ppp packet show dialer
3. 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，则激活备份接口，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，本地也不会激活备份线路。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 number hostname c2522rb ! enable secret 5 $1$J5vn$ceYDe2FwPhrZi6qsIIz6g0 enable password cisco ! username c4700 password 0 cisco ip subnet-zero chat-script cisco-default "" "AT" TIMEOUT 30 OK "ATDT /T" TIMEOUT 30 CONNECT /c chat-script reset atz ! interface Ethernet0 ip address 16.122.51.254 255.255.255.0 no ip mroute-cache ! interface Serial0 backup delay 10 10 backup interface Serial2 ip address 16.250.123.18 255.255.255.252 no ip mroute-cache no fair-queue ! interface Serial1 no ip address no ip mroute-cache shutdown ! interface Serial2 physical-layer async ip address 16.249.123.18 255.255.255.252 encapsulation ppp async mode dedicated dialer in-band dialer idle-timeout 60 dialer map ip 16.249.123.17 name c4700 6825179 dialer-group 1 ppp authentication chap ! interface Serial3 no ip address shutdown no cdp enable ! interface Serial4 no ip address shutdown no cdp enable ! interface Serial5 no ip address no ip mroute-cache shutdown ! interface Serial6 no ip address no ip mroute-cache shutdown ! interface Serial7 no ip address no ip mroute-cache shutdown ! interface Serial8 no ip address no ip mroute-cache shutdown ! interface Serial9 no ip address no ip mroute-cache shutdown ! interface BRI0 no ip address no ip mroute-cache shutdown ! router eigrp 200 network 16.0.0.0 ! ip classless ! dialer-list 1 protocol ip permit ! line con 0 line 2 script dialer cisco-default script reset reset modem InOut modem autoconfigure discovery rxspeed 38400 txspeed 38400 flowcontrol hardware line aux 0 line vty 0 4 password cisco login ! end c2522rb#
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 cisco ip subnet-zero chat-script cisco-default "" "AT" TIMEOUT 30 OK "ATDT /T" TIMEOUT 30 CONNECT /c chat-script reset atz interface Ethernet0 ip address 202.96.38.100 255.255.255.0 ! interface Serial0 ip address 202.96.0.1 255.255.255.0 encapsulation x25 x25 address 10112227 x25 htc 16 x25 map ip 202.96.0.2 10112225 broadcast ! interface Serial1 no ip address shutdown ! ! interface Async 1 ip address 202.96.1.1 255.255.255.252 encapsulation ppp dialer in-band dialer idle-timeout 60 dialer map ip 202.96.1.2 name router2 modem-script cisco-default 2113470 dialer-group 1 ppp authentication chap ! router eigrp 200 redistribute connected network 202.96.0.0 ! ip route 202.96.37.0 255.255.255.0 202.96.1.2 200 dialer-list 1 protocol ip permit line con 0 line aux 0 script dialer cisco-default script reset reset modem InOut modem autoconfigure discovery transport input all rxspeed 38400 txspeed 38400 flowcontrol hardware line vty 0 4 password cisco login ! end 路由器Router2配置如下: hostname router2 ! enable secret 5 $1$T4IU$2cIqak8f/E4Ug6dLT0k.J0 enable password cisco ! username router1 password cisco ip subnet-zero chat-script cisco-default "" "AT" TIMEOUT 30 OK "ATDT /T" TIMEOUT 30 CONNECT /c chat-script reset atz ! interface Ethernet0 ip address 202.96.37.100 255.255.255.0 ! interface Serial0 ip address 202.96.0.2 255.255.255.0 no ip mroute-cache encapsulation x25 x25 address 10112225 x25 htc 16 x25 map ip 202.96.0.1 10112227 broadcast ! interface Serial1 no ip address shutdown ! interface Async1 ip address 202.96.1.2 255.255.255.252 encapsulation ppp keepalive 30 async default routing async mode dedicated dialer in-band dialer idle-timeout 60 dialer wait-for-carrier-time 120 dialer map ip 202.96.1.1 name router1 modem-script cisco-default 2113469 dialer-group 1 ppp authentication chap ! router eigrp 200 redistribute static network 202.96.0.0 ! no ip classless ip route 202.96.38.0 255.255.255.0 202.96.1.1 200 dialer-list 1 protocol ip permit ! line con 0 exec-timeout 0 0 line aux 0 script reset reset modem InOut modem autoconfigure discovery transport input all rxspeed 38400 txspeed 38400 flowcontrol hardware line vty 0 4 password cisco login !
