3825 Capacity

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Aug 13th, 2010
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Hi all,

I am looking at the capacity of the 3825. Reading the SPECS for the router leaves me a little confuse. We currently have 2 3825 routers with 4 PVDMs with 64 channels each. We have 5 PRIs currently configured on each of the routers using VIC2-2MFT-T1/E1 2-port RJ45 Multiflex Trunks. I am going to need to add 9 new PRIs to them resulting in 10 on one and 9 on the other. Are these routers capable of handling these? Could another module be added to the router or is out of capacity and DSP resources? If not is there a router that is capable of handling the traffice or should we add another router of the same size to accommodate the increase?

Thanks for any help.

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Felipe Garrido Tue, 08/17/2010 - 13:13
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It depends on what the voice gateway is currently handling other than the termination of the T1s. The 3825 can physically handle up to 16 T1s. This would require the use of NM-HDV2 modules to fully saturate all available HWIC and NM slots.  The NM-HDV modules also allow for additional DSP resources to be added as the onboard PVDM slots would not be sufficient in a worst case scenario situation. The actual maximum simultaneous calls and calls-per-second depend on what other services are running on the gateway and will be limited by the CPU utilization. I would advise that you contact your Cisco partner or account team to get additional guidance in choosing the correct platform.

The DSP calculator tool can also be used to provide guidance on DSP and interface support on a particular platform.



Mybabesx2 Tue, 08/17/2010 - 13:54
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Thank you for taking the time to respond. I have tried to use the calculator but am not getting a good feel for it's results. Is there a list of how many DSPs each application takes, ie.. t1s, Conference, Transcoding? I might have a better time calculating it that way.

Thanks again


paolo bevilacqua Tue, 08/17/2010 - 14:19
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Do not use that many T1 on a 3825. It is not poweful enough and it is not made for that purpose.

You best choice would a 3925E, or an  AS5400HPX.

Mybabesx2 Tue, 08/17/2010 - 14:32
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We are currently in a hybrid configuration, where the PRI's come in from the PSTN to the Nortel 81C. We then have QSIG and NON-QSIG PRI's connected between the 2 systems. I am looking to possibly have to keep both of them up until we migrate our call center to a VOIP system. So was looking to see what we could add to them in the mean time.

paolo bevilacqua Wed, 08/18/2010 - 02:46
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The risk you take, is to have disservice and the call center goes down.

Even if you are "just adding", better safe than sorry.


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