Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 
New Member

ISDN shared D channel in seperate gateways

I'm a newby to ISDN. Can someone tell me if this will work?

I have two 2651XM voice gateways. Each gateway has a single ISDN circuit. The phone company has the 2 D channels setup as a shared active/failover configuration. The circuit is B8ZF, ESF, NI2. Is this going to work?

Thanks much,



Re: ISDN shared D channel in seperate gateways

Unfortunately, this isn't supported to my knowledge. You can turn up lots of documentation on 'ISDN NFAS' on CCO, which is the technology used to control B channels on multiple PRIs from one D channel, and to support an alternate backup D channel if the first one dies. However, this only works within one gateway, not between multiple gateways.

This sort of thing can be done using SS7 signaling external to both gateways, but this is a rare configuration and usually limited to service providers. It's really unlikely that you can do this.

You could move them both to one gateway and make this work. However, if this is to be configured with CallManager, note that CallManager has no idea how to handle NFAS PRIs so you'll need to use H.323 signaling instead of MGCP. If you're already planning to use H.323 or another technology where the router handles all q.931 signaling, you're fine.

New Member

Re: ISDN shared D channel in seperate gateways

Thanks. I was afraid of that.


CreatePlease to create content