Balance 20 maxing CPU, dropping packets when Cable Modelm active

I just bought a new Balance 20 from Amazon. I have it connected to cable on Wan 2/primary and DSL on Wan 1/failover.

Having cable/Wan 2 connected causes the Balance to max out the CPU after about 1 minute and then latency skyrockets and packets start dropping. If I disconnect cable/Wan 2 (using the Web Admin) then everything runs very smoothly on just DSL/Wan 1.

I have read other threads about setting Physical Interface Speed. I tried ‘1000Mbps Full Duplex’ and also ‘100Mbps Full Duplex’. Both settings produce same result as ‘Auto’, described above. I have also tried disabling Health Check Settings on both WANs to no avail.

When I connect a PC directly to the cable modem, there are no latency or packet loss issues and it runs at full speed. (Anyway, this is observed to be a Balance 20 CPU utilization issue.)

The Cable Modem is a Surfboard SB6190. The Balance 20 Firmware version is 6.3.0.

Any help would be appreciated.


If you log into your Balance and go the the following URL you will be able to see what the link is/isn’t negotiated at:
http://”IP of your device”/cgi-bin/MANGA/support.cgi

Also, set MTU auto and known good cable is being used with LAN/WAN subne being unique. If you are still seeing issues. l would create a support ticket or turn on remote assistance and PM me your SN so I can remote into the unit to check further.