ISDN BRI- 3-site, Full Mesh - DDR w/Dialer Profiles

[ccsn-cnap]

Each of the three routers had the same exact config. except for details such as username/password for CHAP, IP's, phone #'s, etc... The config'd items were the same.

1 BRI int

2 Dialer Ints (dialer profile for each of the other 2 sites)

1 dialer pool

This was in a lab at school and is disconnected now.

However, this issue was I could get the first connection up fine. For example SJ-1 to London and the pings were good. Then, with the 1st connection up I couldn't get the 2nd.

DEBUG showed:

It couldn't dial b/c 2 calls were going on and 2 was the max.

BUT

sh dialer showed the 1st B-channel connected

and the 2nd idle.

The debug output was from the "dialer"

I got it to work by using the "min" parameter in the "dialer-pool member" command. (Set it to 2).

I want to know why this worked. What am I not understanding?

I have read a lot of the DDR and ISDN BRI documentation I could find on Cisco's site and I have re-read the Networking Academy chapter on DDR and ISDN BRI.

I still don't understand why that command made it work.

It seems to me the problem was that the dialer profile did not see any available physical int's to use so, it failed.

(BTW, it started the fast-idle timer right away which makes sense)

Maybe, if I hear/see it explained a couple of different ways it'll sink in.

Thanks in Advance!!

Joshua

[tepatel]

First we need to see what "sh idsn status" and "sh isdn active" reports when the DEBUG reports 2 active calls.

Ideally if you just want one channel to one dialin site, you need to use "dialer max-link 1" command under the dialer profile for each site.

We can take a look on the debug when the router reports two call instead of one. So post

debug dialer

debug isdn q931

debug ppp nego

debug ppp authenticaiton

when the first call is already up and 2nd call fails and two active calls are reported.

[ccsn-cnap]

Unfortunately, I was helping a student with a lab. It is a disconnected and erased now. The student may have saved the config's so we can put them back on next week (Tue - Sat). I was hoping you could explain how it all works. Why, did setting it to min of 2 work? If I set it to 1 would it have worked? It just seemed like the default behavior was that when it went to place a call it looked to see if the 1st channel was available. When it wasn't it then it said it can't make the call; instead of looking and seeing that the 2nd channel was available. If you cleared the line and called the 2nd site first then the same thing happened/ the pings to the 1st are good but it won't dial the 2nd. If you can shed some light it would be appericiated.

Thanks in Advance,

Joshua

[tepatel]

I can try to explain..Min link is to used to reserve the channel for outbound call. So if you have set it to 1, only one outbound call will be allowed and 2nd call will fail. Since you have set it to two, it worked.

If you use "debug dialer" during that time, ios will point that because of min link the 2nd call can't be made.

Again, You can use "dialer max-link" command under the dialer interface (dialer profile) to control the links from the users rather then spredding the links on pool members

[ccsn-cnap]

Thank you. I noticed that the default value for the min is 0 but, the first call to destination 1 worked. That is what confuses me. If the min-link parameter HAS to be configured for it to dial-out then why did the first call work?

Joshua

[tepatel]

There is no need to configure that min link parameter to configure if you don't want to. Min-link may not the the problem here.

As i have mentioned, we need to see the debug and those show commands to see what can be the actual problem.

Here is the link which has a config and troubleshooting for a router dialing out to two different sites using bri lines and dialer profiles.

http://www.cisco.com/warp/public/793/access_dial/isdn800_14562.html

[ccsn-cnap]

Thanks for the link. The only difference was that we only configured one dialer pool. We had 1 BRI card, 2 dialer profiles, and 1 dialer pool. Can that work or do you have to have 2 dialer pools?

Joshua