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
5. Cisco765M通过ISDN拨号上263
由于Cisco765的设置命令与我们常用的Cisco路由器的命令不同，所以以下列举了通过Cisco765上263访问Internet的具体命令行设置步骤。
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:LANcd
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
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-script script-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-script modem-regexp] [system-script 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-script script {dialerreset} script-name
Router1:
hostname Router1
!
enable secret 5 $1$QKI7$wXjpFqC74vDAyKBUMallw/
!
username Router2 password cisco
chat-script cisco-default "" "AT" TIMEOUT 30 OK "ATDT \T" TIMEOUT 30 CONNECT \c
!
interface Ethernet0
ip address 10.0.0.1 255.255.255.0
!
interface Async1
ip address 192.200.10.1 255.255.255.0
encapsulation ppp
async default routing
async mode dedicated
dialer in-band
dialer idle-timeout 60
dialer map ip 192.200.10.2 name Router2 modem-script cisco-default 573
dialer-group 1
ppp authentication chap
!
ip route 10.0.1.0 255.255.255.0 192.200.10.2
dialer-list 1 protocol ip permit
!
line con 0
line aux 0
modem InOut
modem autoconfigure discovery
flowcontrol hardware
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
!
end
