I have AT&T fiber and I bought Eero to help expand the wifi footprint. Issue is that all 4 of the ethernet ports on the modem are being used.
Can I put a switch between the modem and the gateway, then plug the eero and the gateway into the switch?

Can I plug the Eero into the modem then plug the gateway into the Eero?

ATT Modem/Router -> Eero -> Switch

Then log into ATT Router and Disable WiFi

Pman17 said:

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ATT Modem/Router -> Eero -> Switch

Then log into ATT Router and Disable WiFi

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This. You'll also want to put the AT&T modem/router into IP Passthrough mode.

Talked to Eeros support, they recommended getting rid of the switch and pluggimg the gateway into the Eeros. Works just fine like this.