ISDN: DDR Dynamic IP Snapshot Routing

ISDN Dial-On-Demand Sample Configuration Dynamic IP Routing	Cisco ConfigMaker Windows 95/NT 4.0 configuration tool

This sample configuration dynamically routes IP between two Cisco IOS routers using snapshot RIP, and PPP with CHAP authentication over ISDN. With snapshot RIP, routing updates are exchanged between routers during a user configured interval rather than the constant periodic exchange required of normal RIP. 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 #0511

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 ISDN Command Glossary.
Faxback Doc #0551

Detailed descriptions of all IOS commands used in ISDN 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

Preconfiguration Checklist

ISDN Information
The following info must be gathered from the ISDN service provider

ISDN Switch Type
ISDN SPIDs (where applicable)
In North America, SPIDs are required for all ISDN switch types except for 5ESS Custom Point-to-point
ISDN Directory Numbers
The directory number is the local seven digit ISDN phone number (no area codes) of your router

Network Information
The following info must be gathered from the network administrator

PPP Client Name
A PPP client name must be assigned to both locations
PPP Authentication Type
CHAP authentication is preferred and used in this example
PPP Password
A PPP password must be assigned to both locations
IP Address Information
An IP network design must be created
Phone Numbers
ISDN phone numbers of both locations

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
isdn switch-type basic-ni1
!
interface Ethernet0
ip address 10.1.1.1 255.0.0.0
!
interface BRI0
no ip address <*>
encapsulation ppp
dialer rotary-group 0
isdn spid1 014045551111000 5551111
isdn spid2 014045552222000 5552222
no fair-queue <*>
no cdp enable <*>
!
interface Dialer0
ip unnumbered Ethernet0
encapsulation ppp
dialer in-band
dialer idle-timeout 300
dialer map snapshot 1 name Boston speed 56
dialer map ip 20.1.1.1 name Boston speed 56 broadcast 16175553333
dialer map ip 20.1.1.1 name Boston speed 56 broadcast 16175554444
dialer hold-queue 10
dialer load-threshold 200 either
dialer-group 1
snapshot server 15
no fair-queue <*>
no cdp enable <*>
ppp authentication chap
ppp multilink
!
router rip
version 2
network 10.0.0.0
no auto-summary
!
ip classless
ip http server
!
dialer-list 1 protocol ip permit
!
line con 0
password console
login
line aux 0 <*>
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
isdn switch-type basic-5ess
!
interface Ethernet0
ip address 20.1.1.1 255.0.0.0
!
interface BRI0
no ip address <*>
encapsulation ppp
dialer rotary-group 0
isdn spid1 0155533330 5553333
isdn spid2 0155533330 5554444
no fair-queue <*>
no cdp enable <*>
!
interface Dialer0
ip unnumbered Ethernet0
encapsulation ppp
dialer in-band
dialer idle-timeout 300
dialer map snapshot 1 name Atlanta speed 56 14045551111
dialer map ip 10.1.1.1 name Atlanta speed 56 broadcast 14045551111
dialer map ip 10.1.1.1 name Atlanta speed 56 broadcast 14045552222
dialer hold-queue 10
dialer load-threshold 200 either
dialer-group 1
snapshot client 15 600 suppress-statechange-update dialer
no fair-queue <*>
no cdp enable <*>
ppp authentication chap
ppp multilink
!
router rip
version 2
network 20.0.0.0
no auto-summary
!
ip classless
ip http server
!
dialer-list 1 protocol ip permit
!
line con 0
password console
login
line aux 0 <*>
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 ISDN Troubleshooting Assistance
Faxback Doc #isdn_ts