I have one 4-port FXO and one 2-port FXS on my 2811, so when I try to install the second 4-port FXO in the router, then 2-port FXS goes down.
Is there any way to make it work?
So I need two 4-port FXO and one 2-port FXS working on my 2811.
Yep, there are insufficient DSPs to handle the 10 analog ports. The router only has a PVDM2-8 which only supports 8 ports.
PVDM Slot 1:
8-channel (G.711) Voice/Fax PVDMII DSP SIMM PVDM daughter card
You'll need to add additional DSP resources to support the new ports.