Uplink Problems
Find out why a machine on a serial uplink reaches nothing, and use the reopen tally to check the cable.
Checking the Link
An uplink is a serial line that an anchor uses instead of the host's network. On a machine with an uplink, sudo conflux status shows the link before the mode, and shows no host network address:
$ sudo conflux status … uplink /dev/ttyUSB0:115200 — no host network under it mode tun — interface anchor0 …
The missing address is expected, because a serial line has no network addresses.
If the machine reaches nothing over the link, work through these checks in order:
A link connects this machine to exactly one peer. Bring up both ends with
--uplink, and check that theuplinkrow above appears on both machines. An anchor on a cable cannot connect to an anchor on a network socket.
Line Speed
The line must carry a full realm handshake, about 20 to 30 KB, within the 60-second idle timeout. The handshake therefore sets the minimum speed:
| Speed | Handshake | Use |
|---|---|---|
| 115200 | about 2 s | comfortable |
| 57600 | about 4 s | fine |
| 19200 | about 12 s | usable |
| 9600 | about 25 s | marginal against the 60 s idle timeout |
| LoRa or a duty-cycled radio | hours | will not work |
Below 19200 baud, conflux prints a warning and continues:
conflux: 9600 baud carries a realm handshake in about 25s, against a 60s idle timeout.
The Reopen Tally
When the link ends, conflux rebuilds the anchor on it. The machine keeps its identity and does not enrol again. If renewal is due, conflux renews the credential during the rebuild.
| Signal | What conflux does |
|---|---|
| The device is gone from the filesystem | Rebuilds immediately. |
| The anchor has had no connection for 90 seconds | Treats the link as ended and rebuilds. This catches a device that is still present but whose line has failed. |
| A rebuild fails | Tries again, with a wait that grows from one second to thirty seconds. |
The anchor's own uptime resets at every reopen, so conflux counts the reopens in conflux status:
$ sudo conflux status … uplink 7 reopens, last 2026-09-08T11:04:12Z …
- A high tally, such as seven reopens, points to a fault in the cable, a connector or the machine at the other end. Conflux recovers each time, but it cannot fix the fault.
- A link that keeps reopening and never stays up usually means that the machine at the other end is not running. To conflux, an idle link to a machine that is switched off looks the same as a dead link, so it rebuilds after each ninety seconds without a connection. This is harmless, and conflux finds the other machine when it comes back.