You can choose the method and frequency you want the XTM device to use to check the status of each WAN interface. If you do not configure a specified method for the XTM device to use, it pings the interface default gateway to check interface status.
We recommend that you configure one or two link monitor hosts for each external interface. Select targets that have a record of high uptime, such as servers hosted by your ISP. If there is a remote site that is critical to your business operations, such as a credit card processing site or business partner, it may be worthwhile to ask the administrator at that site if they have a device that you can use as a monitoring target to verify connectivity to their site.
If a link monitor host does not respond, it can take from 40–60 seconds for the XTM device to update its route table. When the same Link Monitor host starts to respond again, it can take from 1–60 seconds for your XTM device to update its route table.
The update process is much faster when your XTM device detects a physical disconnect of the Ethernet port. When this happens, the XTM device updates its route table immediately. When your XTM device detects the Ethernet connection is back up, it updates its route table within 20 seconds.
If an external interface is a member of a FireCluster configuration, a multi-WAN failover caused by a failed connection to a link monitor host does not trigger FireCluster failover. FireCluster failover occurs only when the physical interface is down or does not respond.
If you add a domain name for the XTM device to ping and any one of the external interfaces has a static IP address, you must configure a DNS server, as described in
About the XTM Device Route Table