I have two ISPs: Fiber and ADSL
The Fiber Optics transceiver has two Ethernet ports: one is Gigabit Ethernet, the other is Fast Ethernet only. If I connect the Gigabit Ethernet one to WAN 1 on Balance One, once in a while I get a "Disconnected (Link down)" message, immediatelly followed by a "Connected" message. That doesn't happen if I use the Fast Ethernet port. That also doesn't happen on WAN2 with the ADSL modem, which is Fast Ethernet only too.
I though the transceiver was defective. To make sure, I swap the connections, ADSL modem on WAN1 and Gigabit Ethernet from the transceiver on WAN2. After 12 hours,no disconnects.
Is it possible that WAN1 on my Balance One is defective? Unfortunatelly, I don't have another Gigabit Ethernet device to test on it.