DNS resolution failure to CSMS

How it presents

Symptom

DNS resolution failure to CSMS — charger cannot resolve the CSMS hostname; Soft-offline with local Ready possible. protocol field note: keep evidence scrubbed and prove the ranked cause before module RMA on NET-C01.

Root causes (by observed frequency)

1. #1 Site DNS server down or wrong DHCP DNS options

   Entire pad may Soft-offline

2. #2 Modem using unreachable DNS after SIM/APN change
3. #3 Hostname typo in OCPP URL
4. #4 Split-horizon DNS missing the CSMS name

Diagnostic procedure

1. 1. From site network, resolve the CSMS hostname

   Expected: A/AAAA returns

   Tools: dig/nslookup

2. 2. Check charger DHCP DNS servers

   Expected: Reachable resolvers

   Tools: HMI/IT

3. 3. Verify OCPP URL hostname spelling

   Expected: Exact host

   Tools: HMI

4. 4. On cellular, confirm modem DNS/APN DNS settings

   Expected: Works on modem ping

   Tools: modem UI

5. 5. Fix DNS with IT; confirm Heartbeats return

   Tools: CSMS

The fix

NET-C01 is DNS — restore resolution, then Heartbeat, before hardware swaps.

1. Repair site/modem DNS before any board RMA. Document readings and scrubbed photos for NET-C01 before closing the ticket.
2. Correct OCPP hostname typos. Document readings and scrubbed photos for NET-C01 before closing the ticket.
3. Align DHCP DNS options on the EVSE VLAN. Document readings and scrubbed photos for NET-C01 before closing the ticket.
4. Prove resolution then TLS then Heartbeat in that order.
5. Document resolver IPs on the commissioning sheet. Document readings and scrubbed photos for NET-C01 before closing the ticket.