Cheap VWIC-2MFT-E1 in a HWIC slot or expensive NM-HDV-1E1-30E in a NM slot?

Answered Question
Oct 9th, 2008
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I'm using a bundle CISCO2821-CCME/K9 (PVDM2-32). I have a number of IP telephones connected to the router through a switch. I also want to connect to a PABX through a router E1 interface to interoperate with my IP telephones. For the PABX connection I would like to use a cheap VWIC-2MFT-E1 interface card installed in a HWIC slot. Does it work or am I obliged to install an expensive NM-HDV-1E1-30E network card in a NME slot, hosting inside the VWIC-2MFT-E1 interface card? If the NM card is not absolutely necessary, how many voice communications at G.711 and how many at G.729 may I establish simultaneously through the VWIC-2MFT-E1 interface card (having a PVDM2-32)?

Correct Answer by CHRIS CHARLEBOIS about 8 years 9 months ago

The reason anyone uses the NM-HDV modules is to host the DSP resources. The 2600 series routers did not have on-board DSP slots, so the only way to put DSP's on them was via a network module or advanced integration module (AIM). So with the 2800 series, the only reason to use a NM-HDV module is if you need more than the chassis supports, which would only be true if you were doing a massive amount of transcoding or conference bridging, on top of support voice ports. And yes, the DSP calculator is your best option for figuring out if that PVDM2-32 will suffice.

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Correct Answer
CHRIS CHARLEBOIS Thu, 10/09/2008 - 11:06
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The reason anyone uses the NM-HDV modules is to host the DSP resources. The 2600 series routers did not have on-board DSP slots, so the only way to put DSP's on them was via a network module or advanced integration module (AIM). So with the 2800 series, the only reason to use a NM-HDV module is if you need more than the chassis supports, which would only be true if you were doing a massive amount of transcoding or conference bridging, on top of support voice ports. And yes, the DSP calculator is your best option for figuring out if that PVDM2-32 will suffice.

Eugene Cheng Thu, 10/09/2008 - 11:07
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Hi,


I guess if you are using the smaller 2821 router, the VWIC E1 would be sufficient.


The only difference between using the E1 on a VWIC and NM is that the PVDM are either onboard the router or on the NM. For 2821, it doesn't really matter. However for the larger router 3845, the NM is actually hot-swappable while the VWIC is not. It would be much easier for replacement of parts.


For DSP questions, as mentioned, it is best to use the DSP calculator.

Just some help if i remember correctly, a PVDM2-32 have 2 DSP. Therefore, it can support up to 16 medium complexity calls.


http://www.cisco.com/en/US/products/hw/modules/ps2617/products_tech_note09186a008039c316.shtml


Hope that helps.

Eugene

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