Summary
This document addresses a scenario where the wired ISP connection to the Pronto router fails to obtain a valid WAN IP address, causing the device to remain on the cellular backup connection.
In this condition, the Wired WAN interface displays 0.0.0.0 instead of a valid IP address, preventing the router from using the primary ISP connection and stopping the automatic failback from cellular to wired WAN.
When ISP (Wired WAN) is connected to the Pronto router:
Wired WAN IP shows 0.0.0.0
Device remains on Cellular
Failback to ISP does not occur
Scope
This document provides a structured troubleshooting workflow to identify and resolve cases where the Pronto router does not obtain a WAN IP from the ISP modem and remains on the cellular connection.
The scope includes:
Verifying physical connectivity between the ISP modem and the Pronto WAN interface.
Testing DHCP IP assignment from the ISP using a direct laptop connection.
Identifying common ISP-side restrictions such as MAC address lock or DHCP lease conflicts.
Validating router failback behavior from cellular to wired WAN.
Performing proper power cycle procedures to clear MAC or DHCP binding issues.
Determining when the issue should be escalated for further investigation, including packet capture
Possible Causes
Category | Root Cause | Platform Behavior |
ISP | MAC address lock | Common in retail broadband |
ISP | DHCP lease not released | WAN shows 0.0.0.0 |
Router | WAN port negotiation failure | Link light off / unstable |
Router | Health-check failure | WAN IP valid but no failback |
Network | Corporate modem restrictions | DHCP blocked |
Physical | Physical Cable faulty | Link light off / Port status down |
🛠 Troubleshooting Procedure
Step 1 – Verify Physical Connection
Ensure ISP modem is connected to Pronto WAN port.
Check Ethernet cable condition.
Confirm Pronto WAN port link light is active blinking.
Verify device is running latest firmware.
Step 2 – Test ISP DHCP
Connect a laptop directly to the ISP modem.
Result | Action |
Laptop gets IP | Proceed to next step |
Laptop does NOT get IP | ISP issue – contact ISP |
Step 3 – Perform cable test by replacing the cable
If Laptop does not get any IP using same cable connected to Pronto WAN
Replace the Cable, use new cable and connect to ISP to test IP allocation
Try reboot/reset ISP modem and enable/disable Wired NIC adapter of laptop
If Laptop gets IP address, try using same cable on Pronto WAN port
Step 4 – Perform Proper Power Cycle Sequence
Follow exact order:
Reboot/Reset ISP modem.
Reboot/Reset Pronto Device
Disconnect all devices.
Connect Pronto WAN to ISP modem.
Ensure PC61 is powered off
Turn ON ISP modem.
Wait until modem fully boots.
Turn ON Pronto / PC61
Reason: Many ISPs lock DHCP to the first detected MAC address.
Step 5 – Check for MAC Lock / DHCP Lease Issue
If Wired still shows 0.0.0.0 and Laptop does not get IP
Contact ISP and request:
DHCP lease release
MAC address whitelisting
Disable MAC binding (if enabled)
Modem reset from ISP side
Step 5 – Verify Failback Logic
If Pronto WAN uplink gets IP address but switchover not happening
WAN gets valid IP
But device remains on Cellular
Then check:
ICMP communication is not blocked
DNS reachability
Failback requires:
Successful ping/DNS check
Valid response from gateway and additional public destinations.
If ISP blocks ICMP, failback detection may delay.
📌 Root Cause (Most Common)
Upstream ISP modem allowing only one MAC address
DHCP lease not released
PC61 restrictions blocking DHCP or outbound traffic
🚨 Escalation Criteria
Escalate if:
Wired still shows 0.0.0.0 after direct modem test
ISP confirms no MAC restriction
Pc61 rules verified
Reboot sequence properly followed
Generate pcap and verify ip sequence