This sample configuration dynamically routes both IP and IPX using snapshot routing and PPP with CHAP authentication over an asynchronous modem connected to the auxiliary port. With snapshot routing, IP route updates and IPX route and service updates are exchanged between routers during a user configured interval rather than the constant periodic exchange required of normal IP RIP and IPX RIP/SAP. Aside from this snapshot interval, the ISDN line activates only when traffic demands. This is known as dial-on-demand routing (DDR). In contrast, the periodic exchange of normal RIP would force the ISDN line to be permanently active, potentially resulting in high ISDN costs.

An alternative to DDR using a snapshot routing protocol is DDR using static routes. Routing tables are statically created by the network administrator eliminating the need for snapshot routing exchanges. For smaller networks, static routes may suffice. However, for larger networks, manually maintaining static routing tables on every router can be an administrative chore. Fortunately, the duration and frequency of the snapshot routing interval can be configured such that any ISDN costs due to dynamic routing are relatively negligible compared with the benefits of simplified network administration.

Get A DDR Configuration Using Static Routes if static routing is still desired.
Faxback Doc #0557

Info On PPP Faxback Doc #ppp

Info On Snapshot Routing Faxback Doc #snapshot

Info On IP Unnumbered Faxback Doc #ip_unnum

Before You Begin

Get The IOS Async Command Glossary. Faxback Doc #0552 Detailed descriptions of all IOS commands used in Async configurations. Also provides links to the IOS Command Reference if more information is required

Get The IOS Command Line Interface Tutorial Faxback Doc #ios_tutorial Instructions on configuring an IOS router using the command line interface

Note: Commands followed by a <*> are on by default and do not have to be configured. The "!" marks that appear in the configuration are automatically entered by the router and function as line separators for easier reading.

Atlanta Router Configuration
In IOS "show running-config" format

version 11.2 <*>
service udp-small-servers <*>
service tcp-small-servers <*>
!
hostname Atlanta
!
enable secret cisco
!
username Boston password gocisco1
ip subnet-zero
no ip domain-lookup
ipx routing 0000.0caa.1111
chat-script rstmdm "" "AT&FS0=1&B1&C1&D2&H1&K1&M4&R2" OK
chat-script dialnum ABORT ERROR ABORT BUSY "" "ATDT \T" TIMEOUT 60 CONNECT
!
interface Ethernet0
 ip address 10.1.1.1 255.0.0.0
 ipx network 100
!
interface Serial0
 no ip address <*>
 shutdown <*>
!
interface Async1
 no ip address <*>
 encapsulation ppp
 async default routing
 async mode dedicated
 dialer in-band
 dialer rotary-group 0
 no cdp enable <*>
!
interface Dialer0
 ip unnumbered Ethernet0
 ip tcp header-compression passive
 encapsulation ppp
 ipx network AAAA
 dialer in-band
 dialer map snapshot 1 name Boston 16175553333
 dialer map ipx AAAA.0000.0cbb.2222 name Boston broadcast 16175553333
 dialer map ip 20.1.1.1 name Boston broadcast 16175553333
 dialer-group 1
 snapshot server 5 dialer
 no cdp enable <*>
 ppp authentication chap
!
router rip
 version 2
 network 10.0.0.0
 no auto-summary
!
ip classless
dialer-list 1 protocol ip permit
dialer-list 1 protocol ipx permit
!
line con 0
 password console
 login
line aux 0
 script dialer dialnum
 script reset rstmdm
 modem InOut
 transport input all
 rxspeed 38400
 txspeed 38400
 stopbits 1
 flowcontrol hardware
line vty 0 4
 password telnet
 login
!
end <*>

Boston Router Configuration
In IOS "show running-config" format

version 11.2 <*>
service udp-small-servers <*>
service tcp-small-servers <*>
!
hostname Boston
!
enable secret cisco
!
username Atlanta password gocisco1
ip subnet-zero
no ip domain-lookup
ipx routing 0000.0cbb.2222
chat-script rstmdm "" "AT&FS0=1&B1&C1&D2&H1&K1&M4&R2" OK
chat-script dialnum ABORT ERROR ABORT BUSY "" "ATDT \T" TIMEOUT 60 CONNECT
!
interface Ethernet0
 ip address 20.1.1.1 255.0.0.0
 ipx network 200
!
interface Serial0
 no ip address <*>
 shutdown <*>
!
interface Async1
 no ip address <*>
 encapsulation ppp
 async default routing
 async mode dedicated
 dialer in-band
 dialer rotary-group 0
 no cdp enable <*>
!
interface Dialer0
 ip unnumbered Ethernet0
 encapsulation ppp
 ipx network AAAA
 dialer in-band
 dialer map snapshot 1 name Atlanta 14045551111
 dialer map ip 10.1.1.1 name Atlanta broadcast 14045551111
 dialer map ipx AAAA.0000.0caa.1111 name Atlanta broadcast 14045551111
 dialer-group 1
 snapshot client 5 360 dialer
 no cdp enable <*>
 ppp authentication chap
!
router rip
 version 2
 network 20.0.0.0
 no auto-summary
!
ip classless
dialer-list 1 protocol ip permit
dialer-list 1 protocol ipx permit
!
line con 0
 password console
 login
line aux 0
 script dialer dialnum
 script reset rstmdm
 modem InOut
 transport input all
 rxspeed 38400
 txspeed 38400
 stopbits 1
 flowcontrol hardware
 line vty 0 4
 password telnet
 login
!
end <*>

After You've Tried

You've tried the configuration and it doesn't work. Help is available!

Get IOS Router Async Troubleshooting Assistance Faxback Doc #async_ts

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