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DNS Failure – Router Not Coming Online in PCC (Pronto Environment)

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Written by Rohit Yadav

  • 1. Purpose

    This document explains how DNS works on Pronto routers and how to troubleshoot cases where:

    • Internet is partially working (ping is working with IP and failing with FQDN)

    • Router is not coming online in PCC (dashboard)

    DNS fallback ensures the router can recover connectivity automatically even if configured DNS (ISP, Custom) fails.
    ​

    2. Scope

    Applies to:

    • Pronto PC61 routers

    • Sites using Custom DNS or ISP DNS

    • Hospitality / retail deployments

    • Wired, Wireless, and LTE uplinks

    • Router appears DOWN in PCC despite WAN being active

    1. How DNS Impacts Services / Business Continuity

    • Heartbeat (HB) Failure
      Device cannot resolve cloud FQDN → no IP → heartbeat fails → device may appear offline in PCC

    • Payment Failure
      Payment gateway domains cannot be resolved → transactions fail or timeout

    • Business Applications Not Loading
      Applications using domain names fail to load → users see DNS / server errors

    • Overall Impact
      Internet may appear connected, but services do not work → leads to operational disruption

    4. What is DNS Fallback

    DNS fallback is an automatic mechanism where the router switches DNS when the configured one fails.

    When DNS is not working, the router tries:

    • Configured DNS (Primary / Secondary)

    • ISP DNS

    • Public DNS (Google / OpenDNS)

    This helps maintain:

    • PCC (dashboard) connectivity

    • Internet access

    • Captive portal and applications
      ​

    4. Problem Description

    In this scenario:

    • Router is connected to internet

    • But it is not showing online in PCC

    Observed behavior:

    • Internet may partially work

    • Websites may not open

    • PCC shows router DOWN

    • Logs show retry / connection failures
      ​

    Simple Explanation

    The router needs DNS to “find” PCC.

    If DNS is not working, the router cannot locate the cloud, so it stays offline in PCC even though internet is available.

    5. How DNS Fallback Works in Pronto

    1. Identify if Router is in DNS fallback mode

    • As soon as Router boots up, it will try to ping the configured Public IP addresses to check active internet connection

    • If it gets the response, Status LED would be turn into Green immediately, later it will try to resolve HB URL to send the HB communication to PCC portal, if fails unable to receive DNS resolutions for HB URL within 5 min, LED status would turn into Yellow and Router will start the DNS fallback process.

    1. ISP DNS Mode

    When DNS Mode = Use ISP

    • Router uses ISP-provided DNS (via DHCP)

    • If ISP DNS is unreachable/down →
      Router automatically switches to working fallback DNS (It takes around 10 to Min)

    • Fallback may include:

      • Previously learned DNS

      • Public DNS (like 8.8.8.8)

    2. Custom DNS Mode

    • Router first uses configured DNS

    • If it fails → tries ISP DNS

    • If that fails → switches to public DNS (like 8.8.8.8) and then the final fallback happens(During the process events relating to the fall back would be recorded in the events logs)

    This process is automatic
    No manual action required

    Important

    • Fallback takes time (~10 minutes)

    • During this time:

      • Router show DOWN in PCC

      • Logs show retry failures

    After fallback:

    • DNS starts working

    • Router comes UP in PCC

    6. Symptoms of DNS Issue

    • Internet connected but websites not loading

    • PCC shows router DOWN

    • Ping to IP works (8.8.8.8)

    • Ping to domain fails (google.com)

    • Logs show heartbeat retry

    7. How to Test

    • Method 1 – Simple Check
      ​Open the Network Device → Diagnostics → Tools

      • Ping 8.8.8.8 → Works

      • Ping google.com → Fails

      • Check LED status if turns to Yellow

    This Confirms the DNS issue

    Method 2 – Force Test (PC61 connected behind the ISP Router)

    Go to Uplink config and set the DNS to custom

    Use any fake private IP which does not existing in your environment, wait for 10-15 min for the fallback to complete.

    Method 3 – Force Test (in case you want to test on downstream device such as AP or PC61)

    • Set wrong DNS in VLAN (Custom mode)

    • Save configuration

    Expected:

    • Initial failure

    • After few minutes → fallback DNS used

    • Internet restored
      ​

    8. Resolution Actions

    • Use valid DNS:

      • 8.8.8.8

      • 8.8.4.4

      • 1.1.1.1

    • Or set DNS Mode = Use ISP

    • Ensure:

      • WAN Network Access = Enabled

      • NAT = Enabled
        ​

    9. Verification

    After fix:

    • Router shows UP in PCC

    • Websites load normally

    • No DNS errors in logs

    • Stable connectivity
      ​

    10. Preventive Best Practices

    • Always configure Primary + Secondary DNS

    • Use at least one public DNS

    • Avoid wrong DNS entries

    • Monitor logs for DNS failures
      ​

    11. Escalation

    Escalate if:

    • Router stays DOWN even after 10–15 minutes

    • DNS fallback happens repeatedly

    • Multiple sites affected

    Provide:

    • DNS configuration

    • Event logs

    • Router details

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