# Error Code 503

In this case, the Web Application Firewall (WAF) is unable to reach the backend server. A probable cause for this issue is that the backend server is down for maintenance.

To resolve this issue:

1. Check Server Status: Verify if the backend server is undergoing maintenance or experiencing downtime.
2. Monitor Maintenance Schedules: Ensure you are aware of any scheduled maintenance that could impact server availability.
3. Bot Mitigation: If Bot Mitigation is enabled, server or API requests to the application may be blocked by the WAF. To prevent this, whitelist the source IPs under the "Allowed IPs" section in the Bot Mitigation module.

<figure><img src="/files/K87py0O81SHVezPzIfZ8" alt=""><figcaption></figcaption></figure>


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