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isdn link


We have an isdn line which is used only for certain specific use.

1.Is is possible to get an additional public ip with provider for use with this isdn.

2.Because isdn gets a new ip everytime connection is tried, will the additional remain static or will it also change?

3.I'm looking for a static ip which can be used to be used for an application.But the problem with isdn is change in ip eachtime dialing happens and this application needs ip for access.

{EDIT}the application hardware device has the ISDN line directly terminated on it as of now.

looking at possible ways to use this with additional ip, if additional public ip works with isdn.

And after we do get additional ip for isdn,can we simply use it for access.Reason is , the isdn is not terminated on any cisco router currently.If on router, i guess we can have static nat if we router with isdn, is that correct?

if not can we use this?


Hall of Fame Super Silver

Re: isdn link

Hello Sunny,

an ISDN link allows an ISDN DTE To call another ISDN DTE using the E.164 number of the destination.

You can have data service on the bearer channel and also ip services over it.

Usually for DDR dial on demand routing a flat ip subnet is used but it can be a private enteprise address.

Using it as internet access link involving IPCP to have an ip address assigned is still possible but not really attractive.

It can be useful as an out of band backup link to be used to access the site when primary data links are down for a major outage.

But for this you don't need a public ip address you just need another ISDN DTE on HQ or other site and you deploy a private ip subnet over it.

This is because ISDN is a circuit based technology so you don't need to traverse the public internet and to use NAT to use it for DDR.

Besides this, if this application uses it in a specific way unless you are going to dismiss it the link is in use.

Hope to help


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