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PC Ethernet addressing for U-Boot TFTP recovery (Belkin RT3200 / Linksys E8450)

When recovering a MediaTek MT7622 unit (Belkin RT3200, Linksys E8450) from U-Boot over TFTP, the stock menu often assumes:

  • DUT: ipaddr ≈ 192.168.1.1
  • TFTP server: serverip ≈ 192.168.1.254

If the PC connected directly to the router has another address on that cable (for example 192.168.0.5/24), U-Boot sends ARP for 192.168.1.254 and no host answers. The console shows ARP Retry count exceeded and TFTP never starts.

If the console shows TFTP from server 192.168.200.1 while our IP address is 192.168.1.1, serverip is stale from lab mesh (TFTP_SERVER_IP / VLAN 200). Your PC is on 192.168.1.254, not 192.168.200.1. In U-Boot run setenv serverip 192.168.1.254, then ping 192.168.1.254, then retry TFTP. Avoid saveenv until you intend to persist values.

Full OKD / menu procedure: Kiss of Death (OKD) on Belkin RT3200.

1. Pick the Ethernet interface

Use the interface that has the cable to the DUT (not Wi‑Fi, not ZeroTier):

ip -br link

Typical names: enp0s25, enx… (USB Ethernet), eth0.

Set a shell variable so the commands below stay generic:

export ETH=enx7cc2c6338d1d   # example: replace with your interface name

2. Assign 192.168.1.254/24 on that interface

Flush old addresses first so no stale 192.168.0.x (or DHCP lease) stays on the link and confuses routing or your own expectations:

sudo ip addr flush dev "$ETH"
sudo ip addr add 192.168.1.254/24 dev "$ETH"
sudo ip link set "$ETH" up

Check:

ip a show "$ETH"
ip -br link show "$ETH"

You should see inet 192.168.1.254/24 on that interface and a live Ethernet link.

NO-CARRIER: same ARP error even with 192.168.1.254

If ip a shows NO-CARRIER and state DOWN on $ETH, the NIC has no physical link. ARP and TFTP cannot work until the cable negotiates (the PC is not “on the wire” with the router).

5: enx…: <NO-CARRIER,BROADCAST,MULTICAST,UP> … state DOWN

Fix (physical layer first):

  1. Router powered on before or right after plugging the cable.
  2. Cable seated on both ends; try another cable if unsure.
  3. Port on the router: recovery docs often use LAN1; if there is no link, try the other Ethernet port (some boards only bring up one PHY in U-Boot).
  4. USB Ethernet dongle: unplug/replug; try another USB port; confirm the adapter’s LED blinks with link.
  5. Re-check until ip -br link shows UP and LOWER_UP (no NO-CARRIER), e.g.:
ip -br link show "$ETH"
# expect: enx…  UP  (not NO-CARRIER / DOWN)

Only then use U-Boot ping / TFTP again.

Then run your TFTP server so it serves the file U-Boot requests (e.g. openwrt-mediatek-mt7622-linksys_e8450-ubi-preloader.bin) from the documented directory. OKD checklist (tftpd-hpa paths): duts-config § OKD prerequisites.

Optional check from U-Boot (serial): ping 192.168.1.254 should succeed before TFTP.

3. Alternative: keep your PC IP, change U-Boot

If you prefer the PC on another address in 192.168.1.0/24 (e.g. 192.168.1.10), configure that on $ETH and in U-Boot:

setenv serverip 192.168.1.10

Use saveenv only if you intend to persist; for a one-off recovery you can omit it.

The DUT and PC must remain in the same /24 as configured in U-Boot (ipaddr / serverip).

4. After recovery

Restore normal networking on the laptop (NetworkManager, DHCP, or remove the static address) so day‑to-day use is unchanged. A reboot clears transient ip addr changes unless you made them persistent in NM.