Help with Cisco 1720 (ISDN DDR Backup)

GByoung · ‎11-14-2002

Hello everyone.

I'm trying to configure a 1720 with a ISDN backup for the serial line.

I have int BRi0 set up like this

no ip address

no ip directed-broadcast

encapsulation ppp

dialer rotary-group 0

isdn switch-type basic-5ess

no fair-queue

no cdp enable

and int Dialer0 like this

ip address negotiated <---- Dialup ISDN using DHCP on ISP side

no ip directed-broadcast

encapsulation ppp

no ip split-horizon

dialer in-band

dialer idle-timeout 300

dialer string 7774660

dialer hold-queue 10

dialer load-threshold 200 outbound

dialer-group 1

no fair-queue

no cdp enable

Lastly my route commands and access-lists

ip classless

ip route 0.0.0.0 0.0.0.0 Serial0

ip route 0.0.0.0 0.0.0.0 Dialer0 250

no ip http server

access-list 101 permit ip any any

access-list 101 permit icmp any any

dialer-list 1 protocol ip permit

All the above works very well. When I take int serial0 off-line, int Dialer0 kicks in and connects via int BRI0.

However no outgoing packets are being routed from the interface connected to the LAN. I can get out from the router, but not from the internal network.

Any help would be appreicated

Greg

lgijssel · ‎11-15-2002

You have a static route with metric 1 configured for serial 0. This will always be preferred over the backup route with a distance of 250.

To get round this issue you can use the command: backup interface dialer0 on s0 but this will only work when the interface goes physically down.

The other (preferrable) solution is that you use a routing protocol to advertise the route over int s0 and a floating static (higher distance than the routing protocol) on the dialer.

GByoung · ‎11-15-2002

Thanks for the sugesstion, but I already have int Dialer0 configured as a backup for int Serial0 interface Serial0 description 768K line to Frontier_AZ backup delay 10 30 backup interface Dialer0 Our provider will not allow us to configure the routers with RIP or such. The reason for the ISDN line is just that. To kick in when the Serial Interface goes physically down.

Greg