DDR 700: Dynamic Snapshot IP Routing To An IOS Router

700 Series ISDN Dial-On-Demand Sample Configuration Dynamic IP Routing To An IOS Router	Cisco Fast Step Windows 95 Configuration Application

Note: Routing protocols are not supported over an unnumbered IP connection. In order for 700 series routers to dynamically route IP, an IP network must be assigned to the ISDN segment.

This sample configuration dynamically routes IP between a Cisco 700 series router and a Cisco IOS router 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 Configuration Using Static Routes if static routing is still desired.
Faxback Doc #0500

As an added convenience, this configuration also includes the option to utilize the 700 series router's dynamic host configuration protocol (DHCP) server feature. With DHCP, the administrative burdens of configuring and maintaining IP information on each workstation can be greatly reduced. Workstations configured as DHCP clients automatically are assigned IP information (e.g. IP address, subnet mask, default gateway, etc.) by the router. The probability of IP configuration errors is greatly reduced when all IP information is controlled from a single point.

Note: DHCP commands may be ignored if the DHCP server feature is not desired.

Info On PPP
Faxback Doc #ppp

Info On Snapshot Routing
Faxback Doc #snapshot

Info On DHCP
Faxback Doc #dhcp

Before You Begin

Get The IOS-700 Command Glossary Faxback Doc #0554 Detailed descriptions of all commands used in the 700 series router sample configurations. Also provides links to the 700 Command Reference if more information is required.
Get The IOS ISDN Command Glossary. Faxback Doc #0551 Detailed descriptions of all IOS commands used in ISDN sample 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

Atlanta IOS 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 address 172.16.1.1 255.255.0.0
encapsulation ppp
dialer in-band
dialer idle-timeout 300
dialer map snapshot 1 name Boston
dialer map ip 172.16.1.2 name Boston broadcast 16175553333
dialer map ip 172.16.1.2 name Boston broadcast 16175554444
dialer hold-queue 10
dialer load-threshold 200 either
dialer-group 1
snapshot server 5
no fair-queue <*>
no cdp enable <*>
ppp authentication chap
ppp multilink
!
router rip
version 2
network 10.0.0.0
network 172.16.0.0
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 <*>

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.

Boston 700 Series Router Configuration Script

After You've Tried

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

Get 700 Series Router Troubleshooting Assistance
Faxback Doc #700_ts

Get IOS Router ISDN Troubleshooting Assistance
Faxback Doc #isdn_ts