问：用cisco3660、2500两台路由器其中3660走DDN做主线路，2500走拨号备份DDN线路（GVC33.6外猫）客户端使用MP2600终端服务器，s2 口走DDN，s1走拨号（用2600的内猫）如何配置拨号线路 ？
答：gaugin (Cisco 2500) - Calling Router
gaugin#show running-config
Building configuration...
Current configuration:
hostname gaugin
username sphinx password 0 cisco
!
chat-script CALLOUT "" "atdt\T" TIMEOUT 60 CONNECT \c
modemcap entry usr:MSC=&FS0=1&C1&D2&H1&R2&B1&W
interface Loopback1
ip address 1.1.1.1 255.255.255.255
!
interface Serial0
ip address 3.3.3.1 255.255.255.0
!
interface Serial2
physical-layer async
ip unnumbered Loopback1
encapsulation ppp
dialer in-band
dialer map ip 2.2.2.1 name sphinx modem-script CALLOUT 8029
dialer-group 1
async mode dedicated
no peer default ip address
no fair-queue
ppp authentication chap callin
ip route 2.2.2.1 255.255.255.255 Serial0
ip route 2.2.2.1 255.255.255.255 Serial2
dialer-list 1 protocol ip permit
line 2
script dialer CALLOUT
modem InOut
modem autoconfigure type usr
transport input all
speed 115200
flowcontrol hardware
sphinx (Cisco 2500) - Called Router
sphinx#show running-config
Building configuration...
Current configuration:
!
version 12.0
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname sphinx
username gaugin password 0 cisco
modemcap entry usr:MSC=&FS0=1&C1&D2&H1&R2&B1&W
!
interface Loopback1
ip address 2.2.2.1 255.255.255.255
no ip directed-broadcast
!
interface Serial0
ip address 3.3.3.2 255.255.255.0
!
interface Serial2
physical-layer async
ip unnumbered Loopback1
no ip directed-broadcast
encapsulation ppp
dialer in-band
dialer-group 1
async mode dedicated
no peer default ip address
no fair-queue
no cdp enable
ppp authentication chap
ip route 1.1.1.1 255.255.255.255 Serial0
ip route 1.1.1.1 255.255.255.255 Serial2 2
! --- The 2 here is important since the async interface will be in spoofing mode
! --- (not in standby mode). If we do not use the 2 here, we lose half of the
! --- packets in the return path.
line 2
modem InOut
modem autoconfigure type usr
transport input all
speed 115200
flowcontrol hardware