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Beginner

Maximum number of PRI supported on single 2911 or 2921 router

We are in the process of migrating from standalone PBXs to centralized UC. We have several of our remote locations converted and looking to tackle our corporate location. One question we have not been able to research and answer is the number of PRIs that can be supported by a 2911, 2921 or 4300 router. We have a single PRI terminated on 2900s at our remote locations but here at corporate our existing PBX has three PRIs attached. We can find things about the type of VWIC cards and we do use the 4-port at our remote locations but with only one PRI attached. We can find nothing about a maximum number or anything similar. Can anyone provide or point us in the direction for a data sheet that has thins information?

 

Along the same lines anything on configuring multiple PRIs on a single router? I have come across a reference about a PRI-Group but still researching.

 

Brent

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13 REPLIES 13
Cisco Employee

Re: Maximum number of PRI supported on single 2911 or 2921 router

ISR-2900 boxes have 4 EHWIC slots which can have 4 * T1/EI cards. You can use previous generation NM modules through a SM-NM adapter as well to break up the the physical slots into subslots for further scaling.

ISR-4300 series routers range from 2 to 3 NIM slots which can have 2/3 * NIM T1/E1.

You would need PVDM's. With ISR-G2, there are 3 DIMM slots on the motherboard. With ISR-4k, things changed. Every T1/E1 NIM will need to have a dedicated PVDM4 on it so that TDM can be functional. Motherboard PVDM's cannot be used for TDM on ISR-4k.

https://www.cisco.com/c/en/us/products/collateral/routers/2900-series-integrated-services-routers-isr/data_sheet_c78_553896.html

https://www.cisco.com/c/en/us/products/collateral/routers/4000-series-integrated-services-routers-isr/datasheet-c78-732542.html

The above data sheets should give you more information.



Nipun Singh Raghav
"We cannot solve our problems with the same thinking we used when we created them"
Cisco Employee

Re: Maximum number of PRI supported on single 2911 or 2921 router

I overlooked your other query regarding multiple PRI's. You can use a pri-group in order to bundle multiple PRI's. This would save you not having to create dial-peers for every PRI circuit.
Further, if you plan to use MGCP, then CUCM will take care of this.


Nipun Singh Raghav
"We cannot solve our problems with the same thinking we used when we created them"
Beginner

Re: Maximum number of PRI supported on single 2911 or 2921 router

So I should be able to use say 4-port cards in each slot for total of 16? When I use the PVDM calculator we continually get an error message about the number of lines on te platform which is what started the question in the first place. I figure there should be a correlation between the two just cannot find it.


VIP Advisor

Re: Maximum number of PRI supported on single 2911 or 2921 router

That would be very expensive, as you would have to use the super dense DSP.


It would be far cheaper to use a pair of chassis to achieve this.
Cisco Employee

Re: Maximum number of PRI supported on single 2911 or 2921 router

Which 2900 platform you have with you ? I will run it against the DSP calculator and share the output here.

Nipun Singh Raghav
"We cannot solve our problems with the same thinking we used when we created them"
Beginner

Re: Maximum number of PRI supported on single 2911 or 2921 router

We would be using a 2921.


Cisco Employee

Re: Maximum number of PRI supported on single 2911 or 2921 router

SNIP.PNG

 

Going by the calculator, it is recommending a PVDM3-128. This is without any transcoding, CFB, DSP sharing, secure voice etc and for 72 Low Complexity codec calls aka G711ulaw. But you can go with a PVDM3-64 and a PVDM3-16 just fine IMHO.

 

 

Nipun Singh Raghav
"We cannot solve our problems with the same thinking we used when we created them"
VIP Advisor

Re: Maximum number of PRI supported on single 2911 or 2921 router

The answer is more a question of how many channels can be supported. And this depends on the codec being used. G711 gives you the most channel capability. Basically the amount of DSP you put into the platform controls the number of channels it can handle.

For example, this page talks about the DSP you can put into 4000 series routers (you should not be buying 2900 series routers any more). Different models of 4000 have different number of slots, so check out the slots for the model you are interested in and then you can see the maximum DSP you can put in.
https://www.cisco.com/c/en/us/products/collateral/routers/4000-series-integrated-services-routers-isr/data_sheet_c78-728307.html
Beginner

Re: Maximum number of PRI supported on single 2911 or 2921 router

The only reason we are looking at the 2900 platform is that we have one on the shelf we can use to get things up and running as part of a facility move until the new 4000 model is purchased, arrives and get configured. We figure there was a correlation between DSP and channels but having issues with the DSP calculator complaining about too many lines for platform type thing if I remember the error message correctly. That is what started the whole research question in the first place.


VIP Advisor

Re: Maximum number of PRI supported on single 2911 or 2921 router

Be aware the the amount of DSP you are talking about will cost considerably more than the cost of a 2900 or 4000 chassis.
Beginner

Re: Maximum number of PRI supported on single 2911 or 2921 router

We are thinking one 4-port card with the three PRIs as long as we can get the number of DSPs correct.

Cisco Employee

Re: Maximum number of PRI supported on single 2911 or 2921 router

For 3 PRI's, it would need you at least 72 DSP channels. You can get away with a PVDM3-64 and a PVDM3-16 with some about 8 DSP channels left. You should be good with these 2 PVDM's if you do not want to have any sort of a IOS Hardware based media resource i.e. HW CFB, HW MTP and Transcoder.

Nipun Singh Raghav
"We cannot solve our problems with the same thinking we used when we created them"
VIP Advisor

Re: Maximum number of PRI supported on single 2911 or 2921 router

Well, it is 72 DSP resource for a 24 channel PRI (like what is used in the US).

It is 93 DSP resources for a 31 channel PRI (like what is used in most of the reset of the world).

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