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New Member

Unwanted ISDN DDR calls

I’ve had an annoying issue for a while now. We use 1603’s to dial into a 3640, using ISDN DDR. DDR is configured to allow a call to be initiated from either end.

If both routers dial at about the same time they don’t seem to be aware that a connection has already been made (or is being negotiated). The end result is that we sometimes have two dial-up connections when we only want one (we’re not using multilink), performance often suffers when this occurs.

The 3640 is configured with multiple dialer interfaces and the 1603’s are configured using a dialer map, so nothing fancy there.

Is there any way to make sure that a dial-up connection isn’t in place, before a call is made?



Re: Unwanted ISDN DDR calls

With bi-directional DDR, there is always a small chance that both ends will dial/connect at the

same time. If you don't have MPPP enabled (for this particular link), and you don't want more than one B-channel connecting (sounds like it), then you may want to limit this connection to 1 B-channel. You can do this a few ways:

- dialer profiles, using the "dialer max-link 1" command

- MPPP, using the "ppp multilink link max 1" command

- for local authentication, you can use "username foo user-maxlinks 1" command

New Member

Re: Unwanted ISDN DDR calls

Thanks for that, I’ve still got an issue though, and I suspect that the IOS releases involved are creating problems.

The IOS’s I’m running are:

3640 (hub that all others dial into) – v.12.2(7).

1603s – v.12.0(3) and v.11.2(16).

The commands that you recommended don’t appear in the 1603s’ IOS and I didn’t see an equivalent. I therefore used “ppp multilink link max 1” in the dialer interfaces on the 3640, in the hope that implementing it at one end would help.

I haven’t seen any unwanted connections with routers running v.12.0 since. However the routers running 11.2 seem to bring up both channels quiet often, causing performance issues.

The simple solution might be to upgrade the 1603’s to a suitable version, but with 50+ dotted around Europe and just me to do it that’s a major undertaking! So…

Is there an alternative configuration that I could implement on v.12.0?

Is there a known issue with 11.2 (I’ve decided to upgrade these anyway)?