Can I use a Cisco 1803 Router as an ISDN modem?


I am interested in purchasing a Cisco 1803 router and see that the 1800 series has an ISDN backup option.  I also have an application that specifically uses an existing ISDN line to connect and transmit data.

Can I use the 1803 as my ethernet router and also as a replacement to the existing ISDN modem, or is it an internet backup only?

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yes, you can use the router as the replacement of isdn modem.

Since you already have isdn modem, you can use any linux/windows m/c for routing/proxy, if the scenario is small. Will be a cost saving.

ITPOLAuthor Commented:
Hi, thanks for commenting,

Just to be clear; you're saying that the router can be used as an ISDN modem aswell as normal ethernet routing?  Not one or the other?

How would the PC (with the ISDN requiring application) know to connect using ISDN through the router?  I am assuming here that the only connection between the PC and the router would be the ethernet cable?

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ITPOLAuthor Commented:
Thanks, I guess what I am asking is;

Can it ONLY be used as an isdn backup?
Can it be used as an ISDN backup in the case of ASDL/SDSL failure AND when the DSL is working correctly; use its ISDN functionality to replace the existing ISDN modem (ie. dialup, transmit, disconnect)?.

For further info, the existing ISDN line is only used for transmitting data to the receiving party.  It currently does not provide internet access, however I appreciate this will need to change in order for it to work as a DR solution.


It really depends how you currently use the isdn line is it direct system / system or is it using ppp / ip etc..?

If its the later then yes it should be able to.
It is generally easy to configure ISDN as DSL backup.

The interesting point is to use ISDN for the application.
The application can route the traffic through the ethernet or requires the ISDN directly connected on it?
It needs internet access or dials to a specific number ?
What if DSL is down and ISDN is being used as DSL backup? The application will fail. Is that accepted? Or you want to share the ISDN channels? One channel for DSL and one for the application?

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ITPOLAuthor Commented:
@ Mistralol & Ampranti;

Yes, the application uses a direct approach, it searches for ISDN adaptors on the local machine and uses whatever it finds. The number to dial is configured within the application.  As for the sceanrio where ISDN backup is in use and the application needs to be used, this is not a problem as we will take down the backup connection if neccessary to allow the app to work.  The applciation is only used periodically so shouldnt cause too much issue.  I think my solution is to keep the existing ISDN modem and use the router as backup seperately.  The ISDN boxes have two inputs so that wont be an issue either.

Thanks for your input
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