訪問服務器設置如下： 
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）實例 

此例通過Cisco 2500系列路由器的aux端口實現異步撥號DDR連接。Router1撥號連接到Router2。其中采用PPP/CHAP做安全認證，在Router1中應建立一個用戶，以對端路由器主機名作為用戶名，即用戶名應為Router2。同時在Router2中應建立一個用戶，以對端路由器主機名作為用戶名，即用戶名應為Router1。所建的這兩用戶的password必須相同。 
相關命令如下： 
任務 
命令 
設置路由器與modem的接口指令 
chat-script script-name EXPECT SEND EXPECT SEND (etc.) 
設置端口在掛斷前的等待時間 
dialer idle-timeout seconds 
設置協議地址與電話號碼的映射 
dialer map protocol next-hop-address [name hostname] [broadcast] [modem-script 
modem-regexp] [system-script system-regexp] [dial-string] 

設置電話號碼 
dialer string dial-string 
指定在特定線路下路由器默認 使用的chat-script 
script {dialer|reset} 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 
! 
相關調試命令： 
debug dialer 
debug ppp authentication 
debug ppp error 
debug ppp negotiation 
debug ppp packet 
show dialer 
3. 異步撥號備份DDN專線： 
此例主連接采用DDN專線，備份線路為電話撥號。當DDN專線連接正常時，主端口S0狀態為up，line protocol亦為up,則備份線路狀態為standby，line protocol為down，此時所有通信均通過主接口進行。當主接口連接發生故障時，端口狀態為down，則激活備份接口，完成數據通信。此方法不適合為X.25做備份。因為，配置封裝為X.25的接口只要和X.25交換機之間的連接正常其接口及line protocol的狀態亦為 up,它并不考慮其它地方需與之通信的路由器的狀態如何，所以若本地路由器狀態正常，而對方路由器連接即使發生故障，本地也不會激活備份線路。例4將會描述如何為X.25做撥號備份。 
以下是相關命令： 
任務 
命令 
指定主線路改變后，次線路狀態發生改變的延遲時間 
backup delay {enable-delay | never} {disable-delay | never} 
指定一個接口作為備份接口 
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. 異步撥號備份X.25: 

設置X.25的撥號備份,首先X.25連接的端口必須運行動態路由協議,異步撥號口必須使用靜態路由.本例選擇EIGRP作為路由選擇協議,將靜態路由的Metric的值設置為200,由于EIGRP的默認Metric為90,所以當同時有兩條路徑通往同一網段時,其中Metric值小的路徑生效,而當X.25連接出現問題時,路由器無法通過路由協議學習到路由表，則此時靜態路由生效，訪問通過撥號端口實現。當X.25連接恢復正常時，路由器又可以學習到路由表，則由于 Metric值的不同，靜態路由自動被動態路由所代替，這樣就實現了備份的功能。 
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 
　 

CISCO路由器配置手冊－第三章（路由協議設置：RIP協議） 
一、RIP協議 
　 
RIP(Routing information Protocol)是應用較早、使用較普遍的內部網關協議(Interior Gateway Protocol,簡稱IGP)，適用于小型同類網絡，是典型的距離向量(distance-vector)協議。文檔見RFC1058、RFC1723。 
RIP通過廣播UDP報文來交換路由信息，每30秒發送一次路由信息更新。RIP提供跳躍計數(hop count)作為尺度來衡量路由距離，跳躍計數是一個包到達目標所必須經過的路由器的數目。如果到相同目標有二個不等速或不同帶寬的路由器，但跳躍計數相同，則RIP認為兩個路由是等距離的。RIP最多支持的跳數為15，即在源和目的網間所要經過的最多路由器的數目為15，跳數16表示不可達。