Hi,
I have a asterisk server running at our small business, i will layout our setup then get to my problem:
Asterisk server connected to grandstream gxw-4104 connected to three analog pstn lines. We receive calls on all three lines, starting with the first then rolling over by the phone company. We also use all three to place outbound calls, (would use complete voip, but phone number transfer isn’t available in our area and internet isn’t good enough). Then i have 7 Grandstream GXP 2000 setup and 2 X-lite extensions. I receive 20 - 30 Ms to all gxp 2000 and 1ms to gxw-4104 status under “sip show peers”. The server is running asterisk 1.4.20, and running cent os 5 on a server with 1.5 gig ram, and a dual core processor. The fxo box is running 
rogram-- 1.0.0.55 Loader-- 1.0.0.6 Boot-- 1.0.0.18, and all the phones are running: Program-- 1.1.6.37 Bootloader-- 1.1.6.6.
So onto my problem:
In about the 100 calls a day that we receive, my system will drop anywhere from 0-5 calls a day. When this happens it rings like normal, we answer it and we talk for about a half second then i get a busy signal, it hangs up on the customer. This has happened on every gxp 2000 (we don’t use the xlite softphones to receive calls due to lack of transfer capability).
I would consider myself an advanced beginner to linux, i understand the concepts of linux, but need commands spelled out for me. This system has been up and running since june, and i have always had the problem.
The call dropping is just not good for business.
Any help will be appreciated
Thanks in Advance,
Alex