Why can’t I use both Ethernet ports on the Sagemcom F@st 5681 modem?

In most cases, only one Ethernet port should be used since connecting to both would create two separate networks. Having two networks can cause connection issues since devices need to be on the same network to communicate (for example, a computer and printer, or an EPICO PVR and a mobile device).

Exception for phone adapters

If you’re using one of our Grandstream HT814 or HT818 adapters to add more phone lines, this will be connected to the 1G LAN port on the gateway. In this case, you can use the 10G LAN port to connect to a router or a device that requires an Ethernet connection.