We have an old Netvanta 3430 which is connected to our Cox Business Internet. Our contracted speed is 100M download and 20M upload. When I connect directly to the cable modem, the speed tests show 100M down and 20M up. When I connect to the LAN side of the 3430, the speed tests show 30M download and 9M upload.
I've been searching all over the Internet, Adtran support, and the support community for clues as to what could possibly cause the extreme decrease in speed. I have tried everything in the Troubleshooting Internet Speed Test Issues document, but still getting poor performance.
What else I can try?
*** UPDATE ***
Turns out the throughput of the Netvanta 3430 is only 50Mbps with QoS enabled. With QoS modifications, I was able to get the upload speed to 20Mbps (our contracted rate), but the download rate will still only about 25Mbps... which, added together is a total of about 45Mbps, which is about the max throughput of the unit.
We will be replacing the 3430 here soon.