We want to operate the Jetson Nano only with 100Mbit ETH to keep the power consumption low. The high bandwidth of GBit ETH is not necessary in our application. Which PINs must be connected then and how can this be configured in the software. I cannot get a datasheet of the used ETH controller Realtek RTL81119ICG.
I believe Ethernet has speed negotiation built in. It configures to one of 10/100/1000 connecting based on switch and type of cable.
Or to restrict the modes ethtool in software
rreddy78@jetson:~$ ethtool eth0 Settings for eth0: Supported ports: [ TP ] Supported link modes: 10baseT/Half 10baseT/Full 100baseT/Half 100baseT/Full 1000baseT/Full
rreddy78@jetson:~$ ethtool eth0 -s speed 100
as @rreddy78 suggested, ethernet autonegotation can be turned off over SW and you can select a specific link speed. Please let us know whether this suffices for your use-case.