ISDN
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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
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任务
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命令
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设置ISDN交换类型
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isdn switch-type switch-type1
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接口设置
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interface bri 0
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设置PPP封装
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encapsulation ppp
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设置协议地址与电话号码的映射
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dialer map protocol next-hop-address [name hostname] [broadcast] [dial-string]
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启动PPP多连接
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ppp multilink
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设置启动另一个B通道的阈值
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dialer load-threshold load
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显示ISDN有关信息
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show isdn {active | history | memory | services | status [dsl | interface-type number] | timers}
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注：1.交换机类型如下表,国内交换机一般为basic-net3。
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按区域分关键字
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交换机类型
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Australia
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basic-ts013
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Australian TS013 switches
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Europe
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basic-1tr6
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German 1TR6 ISDN switches
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basic-nwnet3
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Norway NET3 switches (phase 1)
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basic-net3
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NET3 ISDN switches (UK, Denmark, and other nations); covers the Euro-ISDN E-DSS1 signalling system
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primary-net5
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NET5 switches (UK and Europe)
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vn2
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French VN2 ISDN switches
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vn3
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French VN3 ISDN switches
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Japan
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ntt
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Japanese NTT ISDN switches
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primary-ntt
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Japanese ISDN PRI switches
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North America
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basic-5ess
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AT&T basic rate switches
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basic-dms100
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NT DMS-100 basic rate switches
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basic-ni1
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National ISDN-1 switches
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primary-4ess
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AT&T 4ESS switch type for the U.S. (ISDN PRI only)
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primary-5ess
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AT&T 5ESS switch type for the U.S. (ISDN PRI only)
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primary-dms100
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NT DMS-100 switch type for the U.S. (ISDN PRI only)
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New Zealand
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basic-nznet3
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New Zealand Net3 switches
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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:
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任务
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命令
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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。
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dialer map protocol address name hostname class classname dial-string
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设置接口支持PPP回拨
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ppp callback accept
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在全局模式下为PPP回拨设置映射类别
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map-class dialer classname
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通过查找注册在dialer map里的主机名来决定回拨.
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dialer callback-server [username]
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设置接口要求PPP回拨
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ppp callback request
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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: BRI0:1:PPP 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