The objective of this article is to explain how the different health check methods work, and how to configure them.
Health Checks are used to detect the Internet link’s logical connectivity. Without health checks, ISP routing issues may not be detected, thus failover may not perform smoothly.
Health Check Methods:
PING: The router will send a ICMP/PING packet to the specified IP address (or host name) to test WAN connectivity.
DNS Lookup: The router will perform a DNS lookup to the specified DNS server.
HTTP: The router will perform an HTTP request to the specified URLs. Optional with strings to match.
SmartCheck: Available in Cellular/USB WAN, SmartCheck initiates when outbound traffic goes unresponded for 10 seconds. When SmartCheck initiates, it will run an ICMP health check.
Configuring Health Checks
Health Check Settings are located at: Network > Interfaces > WAN > [WAN Connection Name].
Health Check Parameters:
Timeout: During any health check, the router will send a health check packet. The router will wait the specified number of seconds for a response before the health check is considered as failed.
Health Check Interval: This number specifies the period between each health check.
Health Check Retries: This number specified the number of health check attempts the router will make. Upon reaching this number, the link will be considered as failed
Recovery Retries: This specified the number of successful health checks a failed links needs before the link is considered as up again.