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Maximum Supported FXS Ports on EVM-HD


We have a Cisco 3925 router with 1x EVM-HD-8FXS/DID + 2x EM3-HDA-8FXS/DID.

With this combination, base on the following link from CCO:

Does it mean that the total usable FXS port on the router is only 16? Or does this only apply when the ports are configured for DID?

There are other combination on the table that uses non DID FXS module (EM-HDA-8FXS), and they were able to support up to 24 FXS ports.

Appreciate if anybody can clarify.

Thanks and kind regards,


Everyone's tags (3)
VIP Super Bronze

Re: Maximum Supported FXS Ports on EVM-HD

This is referring to the maximum capabilities of a single EVM-HD-8FXS/DID, not the 3925 ISR. The 3925 ISR can support two EVM modules if necessary as long as you supply enough DSPs.

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New Member

Re: Maximum Supported FXS Ports on EVM-HD

Hello Jonathan,

Thanks for you response.

I was referring to the module configuration that we have on Cisco 3925 that has 1x EVM-HD-8FXS/DID + 2x EM3-HDA-8FXS/DID and the maximum FXS ports that we can use in this configuration. Base on that table it is only 16 and not 24.

I wanted to confirm whether 16 is when the FXS ports are use with DID signalling. If we use them plainly as FXS, can we use all of the 24 ports?

BTW, the router has enough DSP's.

Thanks and kind regards,