配置使用Dialer Profile的 BRI备份接口

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已更新: 2005 年 9 月 14 日

文档 ID:5721

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关于此翻译

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开始使用前

使用的组件

本文档不限于特定的软件和硬件版本。

本文档中的信息都是基于特定实验室环境中的设备创建的。本文档中使用的所有设备最初均采用原始（默认）配置。如果您是在真实网络上操作，请确保您在使用任何命令前已经了解其潜在影响。

背景理论

backup interface 命令将接口置于备用模式，直到主接口关闭。欲知备用接口功能的更多信息，参见评估备份接口、浮动静态路由和DDR备份的拨号程序监视。

此示例对备份接口功能使用 Dialer Profiles。使用 backup interface 命令强制将已配置的物理或逻辑接口置于备用模式。使用拨号程序配置文件，只有逻辑接口(拨号程序接口)采用备用模式，而物理接口(BRI)仍然可以用于其他连接，作为其他连接池的成员。有关 Dialer Profiles 的详细信息，请参阅使用 Dialer Profiles 配置 ISDN DDR。

配置

本部分提供有关如何配置本文档所述功能的信息。

配置按需拨号路由 (DDR) 备份包括以下这些不同步骤：

配置 DDR。您可以使用传统 DDR (Dialer Maps) 或 Dialer Profiles。此配置使用 Dialer Profiles。在实施备份配置前验证您的DDR连接正常工作。这允许您在配置备份之前验证所使用的拨号方法、点到点协议(PPP)协商和认证是否成功。欲知基于拨号映射的备份配置，使用BRI和backup interface命令，参见“DDR备份”文件。
配置其中一个路由器以在主链路出现故障时启动 DDR 连接。此配置使用 backup interface 命令来触发拨出。
定义在主链路出现故障时将触发备份连接的相关流量。

欲知更多信息，建议您参见“配置和故障排除DDR备份文件”文件。

注：要查找有关本文档中使用的命令的其他信息，请使用命令查找工具(仅注册客户)。

配置

此配置使用BRI电路备份串行链路。它还在两个路由器之间使用 Open Shortest Path First (OSPF) 路由协议。一旦激活备用连接，您必须保证更新路由表，使用新的备份链路。只有一端 (maui-soho-01) 配置为拨出。另一端 (maui-nas-05) 配置为只接受呼叫。

在此配置中，我们使用串行连接，有一个连接到Cisco 3640路由器的Cisco 1604路由器。两个路由器也通过BRI接口安装，此接口用于备份链路。Cisco 1604 运行的是 Cisco IOS® 软件版本 12.1(5)T，而 Cisco 3640 使用的是 Cisco IOS 12.1(2)。

注意：在配置备份接口和备份延迟命令之前，请配置DDR连接（使用BRI0的拨号程序1）并验证其是否正常工作。这将允许在您配置备份之前，有效管理排除拨号配置文件故障、ISDN、PPP和认证问题。

maui-soho-01 (1600)
maui-soho-01#show running-config Building configuration... Current configuration : 1687 bytes ! version 12.1 no service single-slot-reload-enable service timestamps debug datetime msec service timestamps log datetime msec no service password-encryption ! hostname maui-soho-01 ! logging rate-limit console 10 except errors aaa new-model aaa authentication login default local aaa authentication login NO_AUTHEN none aaa authentication ppp default local !--- Basic AAA configuration for ppp calls. enable secret 5 <deleted> ! username maui-nas-05 password 0 cisco !--- Username for remote router (maui-nas-05) and shared secret(used for !--- CHAP authentication). !--- Shared secret must be the same on both sides. ip subnet-zero no ip finger ! isdn switch-type basic-ni ! interface Loopback0 ip address 172.17.1.1 255.255.255.0 !--- The loopback address will be used by OSPF for the router ID. ! interface Ethernet0 ip address 172.16.1.1 255.255.255.0 ! interface Serial0 !--- Primary Interface backup delay 10 30 !--- Backup link will be activated 10 seconds after primary link goes down. !--- Backup link will be deactivated 30 seconds after primary link is restored. backup interface Dialer1 !--- Interface Dialer 1 will provide backup. Dialer 1 will be placed in Standby !--- until the primary link goes down. ip address 192.168.10.2 255.255.255.252 encapsulation ppp no fair-queue clockrate 64000 ppp authentication chap ! interface BRI0 no ip address encapsulation ppp dialer pool-member 10 !--- Assign BRI0 as member of dialer pool 10. !--- Dialer pool 10 is specified in interface Dialer 1. isdn switch-type basic-ni isdn spid1 51255511110101 5551111 isdn spid2 51255511120101 5551112 ppp authentication chap !--- Use PPP CHAP authentication. ppp multilink ! interface Dialer1 !--- Dialer 1 provides backup for the serial link. !--- This interface will be in standby until the primary link is down. ip address 172.20.10.2 255.255.255.0 !--- Address for the dialer interface. !--- The remote side dialer interface is in the same subnet. encapsulation ppp dialer pool 10 !--- Defines Dialer pool 10. !--- BRI 0 is a member of this pool. dialer remote-name maui-nas-05 !--- Specifies remote router name. !--- This name must match that used by the remote router to authenticate itself. dialer idle-timeout 900 !--- Idle timeout is set to 900 seconds (15 minutes). !--- The link will be disconnected if there is no interesting traffic for 900 secs. !--- Since OSPF hellos are interesting traffic, this will reset the idle timeout !--- and cause the link to stay up until the primary link is restored and the dialer !--- returns to standby mode. dialer string 5552222 !--- Defines the destination routers phone number. dialer load-threshold 80 outbound !--- This sets the outbound load level for traffic at which !--- additional connections will be added to the MP bundle load level. !--- Values range from 1 (unloaded) to 255 (fully loaded). The threshold !--- in this case is 80/255=32%. dialer-group 1 !--- Apply interesting traffic definition from dialer-list 1. ppp authentication chap !--- Use PPP CHAP authentication. ppp multilink ! router ospf 5 !--- OSPF configuration. You can use any routing protocol here without any other !--- changes to the configuration. log-adjacency-changes network 172.16.1.0 0.0.0.255 area 0 network 172.17.1.0 0.0.0.255 area 0 network 172.20.10.0 0.0.0.255 area 0 network 192.168.10.0 0.0.0.3 area 0 ! ip classless no ip http server ! dialer-list 1 protocol ip permit !--- All IP traffic is designated as interesting. !--- This is applied to Interface Dialer 1 using dialer-group 1. !--- OSPF hello packets will trigger the dial. ! line con 0 exec-timeout 0 0 login authentication NO_AUTHEN transport input none line vty 0 4 ! end

maui-soho-01 (1600)

maui-soho-01#show running-config
Building configuration...

Current configuration : 1687 bytes
!
version 12.1
no service single-slot-reload-enable
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname maui-soho-01
!
logging rate-limit console 10 except errors
aaa new-model
aaa authentication login default local
aaa authentication login NO_AUTHEN none
aaa authentication ppp default local

!--- Basic AAA configuration for ppp calls.

enable secret 5 <deleted>
!
username maui-nas-05 password 0 cisco

!--- Username for remote router (maui-nas-05) and shared secret(used for !--- CHAP authentication). !--- Shared secret must be the same on both sides.

ip subnet-zero
no ip finger
!
isdn switch-type basic-ni
!
interface Loopback0
ip address 172.17.1.1 255.255.255.0

!--- The loopback address will be used by OSPF for the router ID.

!
interface Ethernet0
ip address 172.16.1.1 255.255.255.0
!
interface Serial0

!--- Primary Interface

backup delay 10 30

!--- Backup link will be activated 10 seconds after primary link goes down. !--- Backup link will be deactivated 30 seconds after primary link is restored.

backup interface Dialer1

!--- Interface Dialer 1 will provide backup. Dialer 1 will be placed in Standby !--- until the primary link goes down.

ip address 192.168.10.2 255.255.255.252
encapsulation ppp
no fair-queue
clockrate 64000
ppp authentication chap
!
interface BRI0
no ip address
encapsulation ppp
dialer pool-member 10

!--- Assign BRI0 as member of dialer pool 10. !--- Dialer pool 10 is specified in interface Dialer 1.

isdn switch-type basic-ni
isdn spid1 51255511110101 5551111
isdn spid2 51255511120101 5551112
ppp authentication chap

!--- Use PPP CHAP authentication.

ppp multilink
!
interface Dialer1

!--- Dialer 1 provides backup for the serial link. !--- This interface will be in standby until the primary link is down.

ip address 172.20.10.2 255.255.255.0

!--- Address for the dialer interface. !--- The remote side dialer interface is in the same subnet.

encapsulation ppp
dialer pool 10

!--- Defines Dialer pool 10. !--- BRI 0 is a member of this pool.

dialer remote-name maui-nas-05

!--- Specifies remote router name. !--- This name must match that used by the remote router to authenticate itself.

dialer idle-timeout 900

!--- Idle timeout is set to 900 seconds (15 minutes). !--- The link will be disconnected if there is no interesting traffic for 900 secs. !--- Since OSPF hellos are interesting traffic, this will reset the idle timeout !--- and cause the link to stay up until the primary link is restored and the dialer !--- returns to standby mode.

dialer string 5552222

!--- Defines the destination routers phone number.

dialer load-threshold 80 outbound

!--- This sets the outbound load level for traffic at which !--- additional connections will be added to the MP bundle load level. !--- Values range from 1 (unloaded) to 255 (fully loaded). The threshold !--- in this case is 80/255=32%.

dialer-group 1

!--- Apply interesting traffic definition from dialer-list 1.

ppp authentication chap

!--- Use PPP CHAP authentication.

ppp multilink
!
router ospf 5

!--- OSPF configuration. You can use any routing protocol here without any other !--- changes to the configuration.

log-adjacency-changes
network 172.16.1.0 0.0.0.255 area 0
network 172.17.1.0 0.0.0.255 area 0
network 172.20.10.0 0.0.0.255 area 0
network 192.168.10.0 0.0.0.3 area 0
!
ip classless
no ip http server
!
dialer-list 1 protocol ip permit

!--- All IP traffic is designated as interesting. !--- This is applied to Interface Dialer 1 using dialer-group 1. !--- OSPF hello packets will trigger the dial.

!
line con 0
exec-timeout 0 0
login authentication NO_AUTHEN
transport input none
line vty 0 4
!
end

在 maui-soho-01 的配置中，请注意以下几点：

备份链路使用 Dialer Profiles。不使用物理接口(BRI 0)时，允许备份接口（拨号程序1）采用备用模式。当主链路处于活动状态时，允许您使用物理接口(通过把它用作不同拨号池的成员)。有关 Dialer Profiles 的详细信息，请参阅 Dialer Profiles 的配置与故障排除文档。
路由器使用 OSPF 作为路由协议。您也可以使用任何其他路由协议（例如 RIP、EIGRP）。请参阅相应的路由协议配置指南 IPC：第 2 部分：IP 路由协议。确保路由协议配置中包括主要接口网络和备份接口网络，以便信息可以使用路由协议传播。如果您希望使用静态路由而不是路由协议，则使用远程BRI接口的下一跳创建静态路由(根据实际情况，您可以把它创建为浮动静态路由)。
任何 IP 流量都将触发拨号（基于 dialer-list 1 和 dialer-group 1）。由于主链路正常运行时备份链路处于备用模式而无法拨号，因此备份链路在备份接口DDR备份环境中运行良好。因为备份链路要求触发数据流拨通备份链路，以验证您有生成触发数据流的数据流源。在本示例中，OSPF hello 数据包将触发拨号。如果您没有使用路由协议，您可以使用ICMP Ping来拨打备份链路。根据需要来调节相关流量。

maui-nas-05 (3640)
maui-nas-05#show running-config Building configuration... Current configuration: ! version 12.1 service timestamps debug datetime msec service timestamps log datetime msec no service password-encryption ! hostname maui-nas-05 ! aaa new-model aaa authentication login default local aaa authentication login NO_AUTHEN none aaa authentication ppp default local !--- Basic AAA configuration for ppp calls. enable secret 5 <deleted> ! username maui-soho-01 password 0 cisco !--- Username for remote router (maui-soho-01) and shared secret !---(used for CHAP authentication). !--- Shared secret must be the same on both sides. ip subnet-zero ! isdn switch-type basic-ni ! interface Loopback0 ip address 172.22.1.1 255.255.255.0 !--- The loopback address will be used by OSPF for the router ID. ! interface Ethernet0/0 ip address 172.22.53.105 255.255.255.0 ! interface Ethernet0/1 no ip address shutdown ! interface BRI1/0 ip unnumbered Loopback0 !--- Unnumbered to the Loopback 0 address. encapsulation ppp dialer pool-member 20 !--- Assign BRI0 as member of dialer pool 20. !--- Dialer pool 20 is specified in interface Dialer 1. isdn switch-type basic-ni isdn spid1 51255522220101 5552222 isdn spid2 51255522230101 5552223 ppp authentication chap !--- Use ppp chap authentication. ppp multilink ! ! <<-- Unused interface configurations have been removed. ! interface Serial2/0 !--- Primary interface. ip address 192.168.10.1 255.255.255.252 encapsulation ppp no fair-queue ppp authentication chap ! ! <<--Unused interface configurations have been removed. ! interface Dialer1 !--- Dialer 1 provides backup for the serial link. !--- Notice that there is no dialer string on this router. This prevents the NAS !--- from attempting to dialout using the backup circuit when the primary is up. ip address 172.20.10.1 255.255.255.0 !--- Address for the dialer interface. !--- The remote side dialer interface is in the same subnet. encapsulation ppp dialer remote-name maui-soho-01 !--- Specifies remote router name. !--- This name must match that used by the remote router to authenticate itself. dialer pool 20 !--- Defines dialer pool 20. dialer idle-timeout 900 !--- Idle timeout is set to 900 seconds (15 minutes). !--- This is equal to the idle timeout set on maui-soho-01. dialer max-call 4096 dialer-group 1 !--- Apply interesting traffic definition from dialer-list 1. ppp authentication chap !--- Use ppp chap authentication. ppp multilink ! router ospf 5 network 172.20.10.0 0.0.0.255 area 0 network 172.22.1.0 0.0.0.255 area 0 network 172.22.53.0 0.0.0.255 area 0 network 192.168.10.0 0.0.0.3 area 0 default-information originate !--- Transmit ospf default information. !--- This may be required for remote router to use the BRI DDR link. ! ip classless ip route 0.0.0.0 0.0.0.0 Ethernet0/0 no ip http server ! dialer-list 1 protocol ip permit !--- All IP traffic is designated as interesting. !--- This is applied to Interface Dialer 1 using dialer-group 1. ! line con 0 login authentication NO_AUTHEN transport input none line 97 102 line aux 0 line vty 0 4 ! end

maui-nas-05 (3640)

maui-nas-05#show running-config
Building configuration...

Current configuration:
!
version 12.1
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname maui-nas-05
!
aaa new-model
aaa authentication login default local
aaa authentication login NO_AUTHEN none
aaa authentication ppp default local

!--- Basic AAA configuration for ppp calls.

enable secret 5 <deleted>
!
username maui-soho-01 password 0 cisco

!--- Username for remote router (maui-soho-01) and shared secret !---(used for CHAP authentication). !--- Shared secret must be the same on both sides.

ip subnet-zero
!
isdn switch-type basic-ni
!
interface Loopback0
ip address 172.22.1.1 255.255.255.0

!--- The loopback address will be used by OSPF for the router ID.

!
interface Ethernet0/0
ip address 172.22.53.105 255.255.255.0
!
interface Ethernet0/1
no ip address
shutdown
!
interface BRI1/0
ip unnumbered Loopback0

!--- Unnumbered to the Loopback 0 address.

encapsulation ppp
dialer pool-member 20

!--- Assign BRI0 as member of dialer pool 20. !--- Dialer pool 20 is specified in interface Dialer 1.

isdn switch-type basic-ni
isdn spid1 51255522220101 5552222
isdn spid2 51255522230101 5552223
ppp authentication chap

!--- Use ppp chap authentication.

ppp multilink
!

! <<-- Unused interface configurations have been removed.

!
interface Serial2/0

!--- Primary interface.

ip address 192.168.10.1 255.255.255.252
encapsulation ppp
no fair-queue
ppp authentication chap
!

! <<--Unused interface configurations have been removed.

!
interface Dialer1

!--- Dialer 1 provides backup for the serial link. !--- Notice that there is no dialer string on this router. This prevents the NAS !--- from attempting to dialout using the backup circuit when the primary is up.

ip address 172.20.10.1 255.255.255.0

!--- Address for the dialer interface. !--- The remote side dialer interface is in the same subnet.

encapsulation ppp
dialer remote-name maui-soho-01

!--- Specifies remote router name. !--- This name must match that used by the remote router to authenticate itself.

dialer pool 20

!--- Defines dialer pool 20.

dialer idle-timeout 900

!--- Idle timeout is set to 900 seconds (15 minutes). !--- This is equal to the idle timeout set on maui-soho-01.

dialer max-call 4096
dialer-group 1

!--- Apply interesting traffic definition from dialer-list 1.

ppp authentication chap

!--- Use ppp chap authentication.

ppp multilink
!
router ospf 5
network 172.20.10.0 0.0.0.255 area 0
network 172.22.1.0 0.0.0.255 area 0
network 172.22.53.0 0.0.0.255 area 0
network 192.168.10.0 0.0.0.3 area 0
default-information originate

!--- Transmit ospf default information. !--- This may be required for remote router to use the BRI DDR link.

!
ip classless
ip route 0.0.0.0 0.0.0.0 Ethernet0/0
no ip http server
!
dialer-list 1 protocol ip permit

!--- All IP traffic is designated as interesting. !--- This is applied to Interface Dialer 1 using dialer-group 1.

!
line con 0
login authentication NO_AUTHEN
transport input none
line 97 102
line aux 0
line vty 0 4
!
end

验证

本部分所提供的信息可用于确认您的配置是否正常工作。

在服务器 maui-nas-05 (3640) 的配置中，验证以下几点：

该配置与任何拨入配置都类似。就 NAS 而言，备份链路只是另一个传入呼叫。
拨号程序接口没有拨号程序字符串，因此无法拨出。
所有流量都是相关流量。由于备份链路无法以任何方式拨出（请参阅上一个项目符号列表项），因此这是可接受的。如果您增加触发数据流的限制(例如，路由协议不是触发协议)，如果没有触发数据流通过链路，NAS则有可能断开呼叫。在备份情况下，最好是让某一终端(拨出或拨入端)控制备份链路，避免链路不稳定性。

测试备份链路

备份接口要求，甚至在将备份接口考虑为备用模式之前，就应该关闭主接口协议。因此，要在不物理上切断主链路的情况下测试备份链路是不可能的。选项有：

使用 shutdown 命令关闭主接口。但不要对配置了 backup interface 命令的路由器使用 shutdown 命令。这不会使 Cisco IOS 软件对备份链路拨号。通过关闭不带有backup interface命令的路由器上的主要接口，您可以激活备份。在这种方案中，在 maui-soho-01 (1600) 上配置了 backup interface 命令。 因此在 maui-nas-05 (3640) 的主要接口执行 shutdown 命令，可以激活备份链路。
物理上通过拔去电缆或某些等效的方法切断主要连接，从而打开备份接口。

显示命令

输出解释器工具支持某些 show 命令（只限于注册用户），通过它可以查看 show 命令输出的分析。

show isdn status - 确保路由器与 ISDN 交换机正常通信。在输出中，验证第1层状态是否为活跃状态，是否第2层状态=MULTIPLE_FRAME_ESTABLISHED出现。此指令也显示活动的呼叫的数量。
show ip interface brief - 这将在备用模式下显示拨号程序 1（在 maui-soho-01 上）。将拨号1用作备份接口意味着物理接口(BRI0)并不专用于备份。因此，在主链路接通时，不能将 BRI 0 用于普通 DDR。

show 输出示例

下面的输出显示了客户端的路由表。下面的输出显示了主链路处于活动状态时的路由表。

maui-soho-01#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area 
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
       i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
       * - candidate default, U - per-user static route, o - ODR
       P - periodic downloaded static route

Gateway of last resort is 192.168.10.1 to network 0.0.0.0

     192.168.10.0/24 is variably subnetted, 2 subnets, 2 masks
C       192.168.10.0/30 is directly connected, Serial0
C       192.168.10.1/32 is directly connected, Serial0
     172.17.0.0/24 is subnetted, 1 subnets
C       172.17.1.0 is directly connected, Loopback0
     172.16.0.0/24 is subnetted, 1 subnets
C       172.16.1.0 is directly connected, Ethernet0
     172.20.0.0/24 is subnetted, 1 subnets
O       172.20.10.0 [110/1849] via 192.168.10.1, 00:00:10, Serial0
     172.22.0.0/16 is variably subnetted, 2 subnets, 2 masks
O       172.22.53.0/24 [110/74] via 192.168.10.1, 00:00:11, Serial0
O       172.22.1.1/32 [110/65] via 192.168.10.1, 00:00:11, Serial0
O*E2 0.0.0.0/0 [110/1] via 192.168.10.1, 00:00:11, Serial0

show ip route的输出(显示如上)显示使用主链路(serial0)从对等体获取的OSPF路由。 现在，让我们关闭主链路并激活备份链路。

备份链路被激活之后，OSPF表将被交换，使用备份链路的新路由将被安装。此时，流量将流过备份链路。

maui-soho-01#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area 
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
       i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
       * - candidate default, U - per-user static route, o - ODR
       P - periodic downloaded static route

Gateway of last resort is 172.20.10.1 to network 0.0.0.0

     172.17.0.0/24 is subnetted, 1 subnets
C       172.17.1.0 is directly connected, Loopback0
     172.16.0.0/24 is subnetted, 1 subnets
C       172.16.1.0 is directly connected, Ethernet0
     172.20.0.0/16 is variably subnetted, 2 subnets, 2 masks
C       172.20.10.0/24 is directly connected, Dialer1
C       172.20.10.1/32 is directly connected, Dialer1
     172.22.0.0/16 is variably subnetted, 2 subnets, 2 masks
O       172.22.53.0/24 [110/1572] via 172.20.10.1, 00:00:01, Dialer1
O       172.22.1.1/32 [110/1563] via 172.20.10.1, 00:00:02, Dialer1
O*E2 0.0.0.0/0 [110/1] via 172.20.10.1, 00:00:02, Dialer1

故障排除

本部分提供的信息可用于对配置进行故障排除。

调试命令

在发出 debug 命令之前，请参阅有关 Debug 命令的重要信息。

debug dialer -这用于显示关于在拨号程序接口上收到的信息包的 DDR 信息。
debug isdn events - 用于查看发生在ISDN接口用户端上的ISDN活动。
debug isdn q931 - 显示(第3层)路由器和ISDN交换机之间的ISDN网络连接的呼叫建立和拆卸。
debug ppp negotiation - 在协商 PPP 组件（包括链路控制协议 (LCP)、认证和 NCP）时显示有关 PPP 流量和交换的信息。成功的PPP协商将首先开放LCP状态，然后进行验证，最后进行NCP协商。
debug ppp authentication -显示PPP认证协议消息，包括质询验证协议(CHAP)信息包交换和密码认证协议(PAP)交换。如果您发现故障，则请验证是否正确配置了 CHAP 用户名和口令。
debug ppp error - 用来显示与PPP连接协商和操作相关的协议错误和错误统计数据。

排除 DDR 备份故障

在您配置备份接口和备份延迟命令之前，配置和检验DDR连接(拨号程序1和BRI0)适当运行。这允许您在配置备份之前，验证拨号程序配置文件、ISDN、PPP和鉴权是否正常运行。若要对 DDR 链路进行故障排除，请参阅拨号技术：故障排除技术。

即然您已经验证了DDR连接正在适当运行，您便可以执行以下所述的备用故障排除步骤：

关闭主链路。请勿对配置了 backup interface 命令的路由器使用 shutdown 命令。这不会使 Cisco IOS 软件对备份链路进行拨号。通过关闭不带有backup interface命令的路由器上的主要接口，您可以激活备份。在这种方案中，在 maui-soho-01 (1600) 上配置了 backup interface 命令。 因此，对 maui-nas-05 (3640) 的主接口执行 shutdown 命令会激活备份链路。并且，您可以通过拔去电缆或使用等效方法从物理上切断主要连接，从而打开备份接口。
您应该看到一条控制台消息，指明备份接口（接口拨号程序 1）已接通。只有在 backup delay 命令所指定的时间间隔过后，才会出现此消息。在此配置中，备份激活延迟为 10 秒。如果未看到此控制台消息，请检查 backup delay 计时器。
```
*Mar  1 03:37:31.788: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state to down
*Mar  1 03:37:42.719: %LINK-3-UPDOWN: Interface Dialer1, changed state to up
```
使用 show ip route 命令来查看主链路关闭时的路由表。您应该观察到拨号程序 1 的直接连接路由。对远程路由器的拨号程序接口（与接口拨号程序 1 位于同一子网中）的 IP 地址执行 ping 操作。您应看到链路拨号和连接。
- 如果链路未拨号，请验证相关流量定义是否允许 ICMP (ping)。
- 如果链路启用，我们可以推断问题发生是由于没有指定到该子网的数据流。然而，依据到特定主机的ping，强制执行到拨号的备份链路并不现实。若要避免出现此问题，可以为默认流量配置浮动静态路由。
```
maui-soho-01(config)#ip route 0.0.0.0 0.0.0.0 172.20.10.1 200 
```
  上述默认路由具有远程路由器拨号器接口的下一跳地址和管理距离200。如果不存在更好的默认路由（即具有较低的管理距离），则此浮动路由允许路由器将数据包路由到拨号器接口。记住我们以前验证路由到拨号程序接口的信息包导致链路拨号。
如果路由器拨打链路，但不能接通，便不再是DDR备份问题，您应该考虑拨号技术：故障排除技术以获取进一步的帮助。

欲知故障排除的更多信息，参见“配置和故障排除DDR备份”文件中的“排除备份接口故障”部分。

调试输出示例

以下debug输出(从客户端)显示主链路发生故障，备份链路激活：

注：为了打印目的，某些调试输出行被分成多行。

maui-soho-01#show debug

maui-soho-01#debug dialer
Dial on demand events debugging is on
maui-soho-01#debug isdn q931
ISDN Q931 packets debugging is on
maui-soho-01#debug ppp negotiation
PPP protocol negotiation debugging is on
maui-soho-01#debug ppp authentication 
PPP authentication debugging is on
maui-soho-01#
*Mar  1 01:09:24.872: %LINK-3-UPDOWN: Interface Serial0, changed state to down

!--- Primary link is unplugged. !--- Refer to the section Testing the Backup Link for the appropriate procedure.

*Mar  1 01:09:24.880: Se0 IPCP: State is Closed
*Mar  1 01:09:24.884: Se0 CDPCP: State is Closed
*Mar  1 01:09:24.888: Se0 PPP: Phase is TERMINATING [0 sess, 0 load]
*Mar  1 01:09:24.892: Se0 LCP: State is Closed
*Mar  1 01:09:24.892: Se0 PPP: Phase is DOWN [0 sess, 0 load]
*Mar  1 01:09:24.908: Se0 IPCP: Remove route to 192.168.10.1
*Mar  1 01:09:24.916: %OSPF-5-ADJCHG: Process 5, Nbr 172.22.1.1 on Serial0
 from FULL to DOWN, Neighbor Down: Interface down or detached
*Mar  1 01:09:25.864: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0,
 changed state to down

!--- Primary interface line protocol is down. This must happen before the backup !--- interface is brought out of standby.

*Mar  1 01:09:34.824: Di1 DDR is shutdown, could not clear interface.
*Mar  1 01:09:34.840: BR0 DDR: rotor dialout [priority]

!--- Note: The backup interface was activated 10 seconds after the primary !--- link went down. This interval was defined with the backup delay command !--- in maui-soho-01 (1600).

*Mar  1 01:09:34.848: BR0 DDR: Dialing cause ip (s=172.20.10.2, d=224.0.0.5)

!--- OSPF hellos cause the router to dial.

*Mar  1 01:09:34.852: BR0 DDR: Attempting to dial 5552222

!--- Phone number of the remote router that is dialed.

*Mar  1 01:09:34.876: ISDN BR0: TX ->  SETUP pd = 8  callref = 0x0A
*Mar  1 01:09:34.888:         Bearer Capability i = 0x8890
*Mar  1 01:09:34.895:         Channel ID i = 0x83
*Mar  1 01:09:34.903:         Keypad Facility i = '5552222'
*Mar  1 01:09:35.169: ISDN BR0: RX <-  CALL_PROC pd = 8  callref = 0x8A
*Mar  1 01:09:35.177:         Channel ID i = 0x89
*Mar  1 01:09:35.415: ISDN BR0: RX <-  CONNECT pd = 8  callref = 0x8A

!--- Call is connected.

*Mar  1 01:09:35.439: %LINK-3-UPDOWN: Interface BRI0:1, changed state to up
*Mar  1 01:09:35.447: %DIALER-6-BIND: Interface BR0:1 bound to profile Di1
*Mar  1 01:09:35.463: BR0:1 PPP: Treating connection as a callout

!--- PPP negotiation begins.

*Mar  1 01:09:35.467: BR0:1 PPP: Phase is ESTABLISHING, Active Open
 [0 sess, 0 load]
*Mar  1 01:09:35.479: BR0:1 LCP: O CONFREQ [Closed] id 14 len 34
*Mar  1 01:09:35.483: BR0:1 LCP:    AuthProto CHAP (0x0305C22305)
*Mar  1 01:09:35.487: BR0:1 LCP:    MagicNumber 0x10BC0680 (0x050610BC0680)
*Mar  1 01:09:35.491: BR0:1 LCP:    MRRU 1524 (0x110405F4)
*Mar  1 01:09:35.495: BR0:1 LCP:    EndpointDisc 1 Local
 (0x130F016D6175692D736F686F2D3031)
*Mar  1 01:09:35.511: ISDN BR0: TX ->  CONNECT_ACK pd = 8  callref = 0x0A
*Mar  1 01:09:35.566: BR0:1 LCP: I CONFREQ [REQsent] id 6 Len 33
*Mar  1 01:09:35.570: BR0:1 LCP:    AuthProto CHAP (0x0305C22305)
*Mar  1 01:09:35.574: BR0:1 LCP:    MagicNumber 0x30D37ABB (0x050630D37ABB)
*Mar  1 01:09:35.578: BR0:1 LCP:    MRRU 1524 (0x110405F4)
*Mar  1 01:09:35.582: BR0:1 LCP:    EndpointDisc 1 Local
 (0x130E016D6175692D6E61732D3035)
*Mar  1 01:09:35.590: BR0:1 LCP: O CONFACK [REQsent] id 6 Len 33
*Mar  1 01:09:35.598: BR0:1 LCP:    AuthProto CHAP (0x0305C22305)
*Mar  1 01:09:35.602: BR0:1 LCP:    MagicNumber 0x30D37ABB (0x050630D37ABB)
*Mar  1 01:09:35.606: BR0:1 LCP:    MRRU 1524 (0x110405F4)
*Mar  1 01:09:35.610: BR0:1 LCP:    EndpointDisc 1 Local
 (0x130E016D6175692D6E61732D3035)
*Mar  1 01:09:35.618: BR0:1 LCP: I CONFACK [ACKsent] id 14 Len 34
*Mar  1 01:09:35.622: BR0:1 LCP:    AuthProto CHAP (0x0305C22305)
*Mar  1 01:09:35.626: BR0:1 LCP:    MagicNumber 0x10BC0680 (0x050610BC0680)
*Mar  1 01:09:35.630: BR0:1 LCP:    MRRU 1524 (0x110405F4)
*Mar  1 01:09:35.637: BR0:1 LCP:    EndpointDisc 1 Local
 (0x130F016D6175692D736F686F2D3031)
*Mar  1 01:09:35.641: BR0:1 LCP: State is Open
*Mar  1 01:09:35.645: BR0:1 PPP: Phase is AUTHENTICATING, by both
 [0 sess, 1 load]

!--- PPP authentication begins.

*Mar  1 01:09:35.649: BR0:1 CHAP: O CHALLENGE id 6 Len 33 from "maui-soho-01"

!--- This is the username used for outgoing CHAP challenge. The remote router !--- must have this username configured along with shared secret.

*Mar  1 01:09:35.657: BR0:1 CHAP: I CHALLENGE id 6 Len 32 from "maui-nas-05"

!--- This is the username for incoming CHAP challenge. !--- This username must be locally configured.

*Mar  1 01:09:35.760: BR0:1 CHAP: O RESPONSE id 6 Len 33 from "maui-soho-01"
*Mar  1 01:09:35.804: BR0:1 CHAP: I SUCCESS id 6 Len 4
*Mar  1 01:09:35.808: BR0:1 CHAP: I RESPONSE id 6 Len 32 from "maui-nas-05"
*Mar  1 01:09:35.820: BR0:1 CHAP: O SUCCESS id 6 Len 4

!--- CHAP authentication is successful.

*Mar  1 01:09:35.828: BR0:1 PPP: Phase is VIRTUALIZED [0 sess, 1 load]
*Mar  1 01:09:35.844: Di1 DDR: Authenticated host maui-nas-05 with no matching
 dialer map
*Mar  1 01:09:35.848: Di1 PPP: Phase is UP [0 sess, 1 load]
*Mar  1 01:09:35.856: Di1 IPCP: O CONFREQ [Closed] id 6 Len 10
*Mar  1 01:09:35.860: Di1 IPCP:    Address 172.20.10.2 (0x0306AC140A02)
*Mar  1 01:09:35.872: Di1 CDPCP: O CONFREQ [Closed] id 6 Len 4
*Mar  1 01:09:35.876: BR0:1 MLP: maui-nas-05, multilink up, first link
*Mar  1 01:09:35.884: BR0:1 IPCP: MLP bundle interface is built,
 process packets now 
*Mar  1 01:09:35.887: BR0:1 IPCP: Redirect packet to Di1
*Mar  1 01:09:35.891: Di1 IPCP: I CONFREQ [REQsent] id 6 Len 10
*Mar  1 01:09:35.895: Di1 IPCP:    Address 172.20.10.1 (0x0306AC140A01)
*Mar  1 01:09:35.903: Di1 IPCP: O CONFACK [REQsent] id 6 Len 10
*Mar  1 01:09:35.907: Di1 IPCP:    Address 172.20.10.1 (0x0306AC140A01)
*Mar  1 01:09:35.911: BR0:1 CDPCP: MLP bundle interface is built,
 process packets now 
*Mar  1 01:09:35.915: BR0:1 CDPCP: Redirect packet to Di1
*Mar  1 01:09:35.919: Di1 CDPCP: I CONFREQ [REQsent] id 6 Len 4
*Mar  1 01:09:35.927: Di1 CDPCP: O CONFACK [REQsent] id 6 Len 4
*Mar  1 01:09:35.931: Di1 IPCP: I CONFACK [ACKsent] id 6 Len 10
*Mar  1 01:09:35.935: Di1 IPCP:    Address 172.20.10.2 (0x0306AC140A02)
*Mar  1 01:09:35.939: Di1 IPCP: State is Open

!--- IPCP state is open and route will be installed.

*Mar  1 01:09:35.951: Di1 CDPCP: I CONFACK [ACKsent] id 6 Len 4
*Mar  1 01:09:35.955: Di1 CDPCP: State is Open
*Mar  1 01:09:35.959: Di1 DDR: dialer protocol up
*Mar  1 01:09:35.971: Di1 IPCP: Install route to 172.20.10.1

!--- Route to remote side is installed.

*Mar  1 01:09:36.840: %LINK-3-UPDOWN: Interface Dialer1, changed state to up
*Mar  1 01:09:36.844: Di1 LCP: Not allowed on a Dialer Profile
*Mar  1 01:09:36.848: %LINEPROTO-5-UPDOWN: Line protocol on Interface BRI0:1,
 changed state to up
*Mar  1 01:09:41.411: %ISDN-6-CONNECT: Interface BRI0:1 is now connected to 5552222
 maui-nas-05

!--- Connection is up.

*Mar  1 01:09:44.931: %OSPF-5-ADJCHG: Process 5, Nbr 172.22.1.1 on
 Dialer1 from LOADING to FULL, Loading Done

!--- OSPF database exchange is complete.