configuration problem for cisco isdn router 803 as a backup of dsl router

[pan_agra]

i have a cisco 803 isdn router and a isdn link of 128kbps . i want to configure it as a backup for my adsl 3rd party router so anybody help me for a solution

i want to know wether 4 ethernet port of isdn 803 router is manageable or not

then i can use backup intetface command

[tepatel]

Very difficult to configure backup like that. 803 needs to have a some way to know that adsl line connected with the third party adsl modem went down so that it needs to activate isdn line. You can conenct 803 and adsl modem via ethernet using a hub but that way 803 will only have a visibility of the eth port only and eth port will never reflect the status of the adsl line. Eth interface will be up/up the moment you plug in the hub.

All-n-all no way to achive the backup for adsl line if both the routers are connected via ethernet.

[pan_agra]

yes it is dificult but i found a dsl provider url, which is http://support.onyx.net/connections/onyx_adsl_plus/adslplussetup.php3

they are using cisco 803 for the bacup purpose

can you help me for a solution

[tepatel]

You can do that if the adsl line is configured for PPPoE. Where the cisco router act as a PPPoE cleint. But that will be layer 2 backup. I am not sure how Onyx have implemented that.

You can also use "backup interface bri0" commend under the eth interface on cisco router which was connected with adsl modem's eth interface. But again i am not sure how it will reflect the adsl line status on the ethernet interface.

Mostly you should be looking for layer 3 backup where the adsl line lost its ip address. That way if you loose routing over adsl, you can have isdn triggered. Normally adsl line will stay up/up as its a physical layer but may loose layer 3 connectivity.

[pan_agra]

but if i am using backup interface bri0 at my existing cisco 803 under the eth int. it give me unknown command i don't know why

i am using ios 12.0(5).T version with file name c800-y6-mw .

could you help me on this .and also my solution is

i configuring eth 0 as deafault gateway for my internet user with default route ip address of dsl link which is on same 803 hub and now i want to configure

bri0 as a backup interface