Jetson PC wired internet sharing

Use a separate, non-autoconnecting NetworkManager profile on the PC. Keep the original wired profile intact so the operation is easy to reverse. Never put a sudo or SSH password in this skill, a connection profile, a script, or a log.

Start sharing

1. Inspect before changing anything:

   • nmcli device status, active connections, ip -br addr, and ip route.
   • ip route get <jetson-ip> to identify the PC interface carrying SSH.
   • The Jetson's interface, address, routes, and DNS over the existing SSH link.
   • Confirm the PC has a working upstream/default route on a different interface.

2. Determine the downstream PC address:

   • If the Jetson already has a static address and SSH uses the wired subnet, preserve the PC's existing address and subnet. This avoids losing SSH.
   • Otherwise choose an unused RFC1918 /24 that does not overlap any PC or Jetson route; NetworkManager's usual 10.42.0.1/24 is acceptable only after checking for conflicts.

3. Create or update a profile named jetson-wired-share on the downstream interface. Set connection.autoconnect no, ipv4.method shared, the chosen ipv4.addresses, ipv4.never-default yes, and ipv6.method disabled. Then activate it. Do not edit or delete the original wired profile. Example shape:

   sudo nmcli connection add type ethernet \
     ifname <pc-wired-interface> con-name jetson-wired-share autoconnect no \
     ipv4.method shared ipv4.addresses <pc-address/cidr> \
     ipv4.never-default yes ipv6.method disabled
   sudo nmcli connection up jetson-wired-share

   If that profile already exists, use nmcli connection modify instead of creating a duplicate. Warn that activation may briefly flap the wired link.

4. Configure the Jetson without making its static profile persistent unless the user explicitly asks. For an already-static Jetson, add a runtime route:

   sudo ip route replace default via <pc-wired-ip> dev <jetson-interface> metric 100

   Retain any unrelated routes. If DNS is not already usable, set runtime DNS on that interface with resolvectl dns <interface> <pc-wired-ip> when available. If split DNS (commonly Tailscale) still captures public lookups, also use resolvectl domain <interface> '~.' so the wired link routes ordinary DNS. For a DHCP-configured Jetson, renew DHCP instead.

5. Verify from the Jetson, in order:

   • ping the PC's downstream address;
   • ping a public IP;
   • resolve a public hostname;
   • make a short HTTPS request.

   Report the active profile, PC/Jetson addresses, route, and observed test results. Do not claim success based only on a NetworkManager status message.

NetworkManager ipv4.method shared owns DHCP/DNS forwarding and NAT. If it does not work, inspect NetworkManager logs, IP forwarding, and nftables before making additional changes. Do not disable the host firewall wholesale.

Stop sharing

Remove only the runtime Jetson route added by this workflow, deactivate jetson-wired-share, and reactivate the original wired profile discovered at the start:

sudo ip route del default via <pc-wired-ip> dev <jetson-interface> metric 100
sudo resolvectl revert <jetson-interface>
sudo nmcli connection down jetson-wired-share
sudo nmcli connection up <original-wired-profile>

The share profile may remain saved for reuse because it has autoconnect disabled. Delete it only when the user asks. Recheck the original PC-to-Jetson SSH route after restoration.