number of DSPs needed for 5 ISDN PRI interfaces on 2811 platform

Answered Question
Jan 23rd, 2009
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Hi all!


I have one Cisco 2811 router as a VoIP gateway between Telco and my CCM.


Currently, there's one ISDN PRI over 1-port T1/E1 Multiflex Voice/WAN Interface Card. There is PVDM2-32 module also and everything works fine so far.


Now I need to connect to CCM the four additional ISDN PRI interfaces from telco.


My question is can I achieve it on this router with:


1. adding two 2-port T1/E1 Multiflex Voice/WAN Interface Cards and


2. upgrading to two modules PVDM2-64 in total?


or


maybe should I go with a new router (which is less desired solution)?


In other words, would it be a problem to have 5 PRI interfaces with 2x PVDM2-64 modules in total on 2811 platform. Would it be enough?


TIA

Zoran Milenkovic

Correct Answer by paolo bevilacqua about 8 years 5 months ago

I realized my mistake and corrected my reply.

The point is that if you don't have enough DSP, you cannot configure the PRI interface at all, so as I said either get a bigger router, or install an NM-HDV2-xx.


Correct Answer by paolo bevilacqua about 8 years 5 months ago

Hi, you cannot use only PVDM2 on 2811 for 5 x E1, because the the 2811 has only two PVDM2 slots, and you need 3.


5 x 30 = 150 channels, 2 PVDM2-64 makes only 128 channels.


So, eithjer replace the router with abigger one, or use the PVDM2 on borad in conjuction with an NM-HDV-xxx.


If you have service contract, you can use the online DSP calculator for this kind of things.



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Correct Answer
paolo bevilacqua Fri, 01/23/2009 - 03:16
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Hi, you cannot use only PVDM2 on 2811 for 5 x E1, because the the 2811 has only two PVDM2 slots, and you need 3.


5 x 30 = 150 channels, 2 PVDM2-64 makes only 128 channels.


So, eithjer replace the router with abigger one, or use the PVDM2 on borad in conjuction with an NM-HDV-xxx.


If you have service contract, you can use the online DSP calculator for this kind of things.



mizoran78 Fri, 01/23/2009 - 03:30
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Thanks for answering but 2811 has only two PVDM2 slots :( That means that I can have two PVDM2-64 modules at maximum!


So if I have 5 ISDN PRI interfaces, I am wondering would it be enough?


Can we assume those two PVDM2-64 modules as a kind of 80% coverage of ISDN interfaces by DSP resources or not? Somebody with experience in similar scenario?


Thanks,

Zoran Milenkovic

Correct Answer
paolo bevilacqua Fri, 01/23/2009 - 03:54
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I realized my mistake and corrected my reply.

The point is that if you don't have enough DSP, you cannot configure the PRI interface at all, so as I said either get a bigger router, or install an NM-HDV2-xx.


mizoran78 Fri, 01/23/2009 - 04:03
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That's exactly what I wanted to know!


Thanks!


Zoran Milenkovic

paolo bevilacqua Fri, 01/23/2009 - 04:21
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Thank you for the nice rating and good luck!

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