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Home > Archive > CCNP > November 2000 > How to bundle multiple PRI's using one D channel?
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How to bundle multiple PRI's using one D channel?
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| I am in the process of configuring a AS5300 with 3 PRI's for a remote dialin solution. I was wondering if anyone knows how to associate 3 PRI's to one D-channel. I have configured each Controller T1 independently with the correct Linecoding, framing, and clocksource, but instead of configuring a D-channel for each I want to use on D-channel for all three.
Is this possible?
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| You can't use just one D channel for all lines. You will actually need to use two. One's the primary and one is the secondary. Only one is used at a time, but you need to have the back up around.
It's called NFAS: Non-Facility Associated Signaling, if I recall correctly. It's a pretty neat trick, but it has to be supported by your provider and they have to set up all the hard setup parts. Once they have their bit configured, you just assign all the controllers to a single group and specify the primary and secondary (the telco will tell you which circuits these are) and configure a single D channel on the 5300. In the end, it looks a bit like this:
controller T1 0
framing esf
clock source line primary
linecode b8zs
pri-group timeslots 1-24 nfas_d primary nfas_int 0 nfas_group 0
!
controller T1 1
framing esf
clock source line secondary 1
linecode b8zs
pri-group timeslots 1-24 nfas_d backup nfas_int 1 nfas_group 0
!
controller T1 2
framing esf
clock source line secondary 2
linecode b8zs
pri-group timeslots 1-24 nfas_d none nfas_int 2 nfas_group 0
!
controller T1 3
framing esf
clock source line secondary 3
linecode b8zs
pri-group timeslots 1-24 nfas_d none nfas_int 3 nfas_group 0
!
controller T1 4
framing esf
clock source line secondary 4
linecode b8zs
pri-group timeslots 1-24 nfas_d none nfas_int 4 nfas_group 0
!
! more interfaces....
!
interface Serial0:23
no ip address
encapsulation ppp
ip mroute-cache
dialer rotary-group 1
isdn switch-type primary-dms100
isdn incoming-voice modem
no cdp enable
I configured this on an AS5300 with 8 PRI's so we gained an additional 6 channels for use. Whoopee.
Cisco has several illustrative config examples on their Access Dial Cookbook. Just look for NFAS.
Let me know if you have other questions and I'll do my best. I learned more about ISDN than I ever wanted to know when I did this.
MadChef
[This message has been edited by MadChef (edited 11-28-2000).]
[This message has been edited by MadChef (edited 11-28-2000).] | |
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| Thanks Madchef for the information. I will checkout Cisco's Cookbook.
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| Wow!
How come that kind of questions are NEVER answered by the superior inteligences that need one week of studying for a CCNP exam, and at times they even write two exams a day?
My best guess is that the superior inteligences reserve themselves for better applications than such a trivial, daily task of "how to associate 3 PRI's to one D-channel"...
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| I understand your point totally, transilvanian (isn't that usually spelled with a 'y'?). But you have to admit that the NP exams really only test the basics of each subject. Granted, the basics may not be all that easy, but Cisco doesn't go into depth with the subjects like they could.
NFAS is a kind of odd-ball technology. Unless you're dealing with big RAS servers or an ISP, you probably don't come into contact with it at all. I would expect that people who are comfortable with NFAS probably don't study for something like BCRAN at all. Maybe there were dozens of folks ready to respond to this and I just beat them to it.
The cert matters, but it sure doesn't matter as much as the knowledge.
All who have configured NFAS, say aye.
Aye,
MadChef
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| MadChef comes thru again and I'm real impressed!
In addition to the great technical info, MadChef slid in another great point I think should be stressed heavily. He said something to the effect "This project made me learn more about ISDN then I cared to know".
If your goal is just to pass the tests and get the certification, that's relatively easy and can be done just by reading the books, but if you want to be a very good tech you need to have a job that presents you with interesting projects like the one MadChef described to you. I'll bet Mad entered that project cheerfully, struggled for a while, searched the CCO, got frustrated, searched for more info and maybe even opened a case with Cisco's TAC for assistance before finally completing it. My point is that these things are what really teach you to be a great tech and get you the experience to pass the CCIE lab. Books and home labs alone are sufficient for the basics, but it's the hair pulling projects you take on that really get you the experience necessary to be good.
Maybe I'm wrong on this project and things sailed smoothly right along for MadChef, but I'm sure he understands exactly what I mean.
Thanks again MadChef!
Yankee | |
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| I had no idea you could do this sort of thing prior to that project. Someone told me I had to use NFAS, so I started cruising CCO for info and found some really great examples. Configuring wasn't the hard part, it turned out. The hard part was working with Cisco and the telco for a week trying to fix what turned out to be an IOS bug that prevented proper failover to the secondary D channel. I saw so much debug output that my started to dream about q931 call set up and teardown. After that, I certainly didn't sweat the ISDN stuff when it came to BCRAN.
So yeah, Yankee. I did all those things. Especially the frustrated part.
MadChef | |
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| LOL I had a similar experience where my ISDN carrier kept telling me it was my problem because the D channel call was going thru and even if the B channels never came up it must be my fault. I did more debug ppp negotiation then any human should have to endure only to find out (as I thought all along) that the carrier had configed the wrong long distance carrier on their switch.
I did well on the ISDN stuff on the Cisco exams too but I was more frustrated then I care to admit!
Yankee |
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