X. WAN

Ping Detect

Ping Detection is the more advanced of the WAN Connection Detection modes. It is designed to ping one or more target IP addresses. If there's no response, the WAN connection fails a "WAN Health Check" and the WAN interface goes off-line until the target IP starts responding again.

To display the options shown, select "Ping Detect" as a WAN Connection Detection option.

Ping IP:

The Ping IPs shown here are examples and will not work in a real setup.

The IP address used should be one that gives 100% uptime and responds to pings, for instance:
- IP address of a Web site or Remote site required for normal operations
- Popular Internet DNS servers

To find IPs of hostnames / websites, try this command in a Windows Command Prompt to see which IP addresses are associated with it:

nslookup www.example.website

If setting up Ping Detect with the IP address result of a hostname, please note that that IP could change and no longer respond, resulting in the WAN Connection check failing. Setting a Secondary Ping IP to a different location would avoid this issue.

TTL - Time To Live:

The TTL setting controls the number of "hops" allowed between the router and the target IP(s). That is, the number of routers / gateways that the packet passes through.
For instance a TTL of 10, or 10 hops, would pass through 10 different gateways to reach the target IP, which is typical for international traffic.

This can be useful to detect / react to routing issues such as traffic taking a longer than normal path, but if set lower than the required number of hops, would result in the WAN interface going off-line, even though the IP address is responding without issue.

It's possible to find the number of hops required to reach a site with Trace Route ("tracert" in the Windows Command Prompt) but setting a more relaxed value such as 30-100 is recommended to handle normal network routing changes. Setting the highest value of 255 is best when this isn't necessary.

Ping Interval & Ping Retry:

Setting a high Ping Interval and high number of Ping Retries will increase the amount of time to detect that the WAN connection has failed and make it less sensitive to brief losses of connectivity and packet loss. The default values will send a ping every second and if one ping fails, the router will allow up to 10 more failures before considering the WAN off-line. This results in roughly 15 seconds wait between the first ping failure and the WAN being taken off-line.

Setting a low Ping Interval and low Ping Retry count will make the WAN Connection Detection sensitive to packet loss or brief disconnections and could take the WAN off-line if there is significant packet loss.

Sending a ping every second will use roughly 20MB of data per day, which could be an issue on metered Internet connections (3G / 4G LTE).
It is recommended to tune these settings depending on your requirements.

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The configurable options are:

	Description
Primary Ping IP	Primary IP address to ping, if this does not respond, the router checks the Secondary Ping IP (not available in all firmware versions)
Secondary Ping IP (not available in all firmware versions)	Secondary IP address to ping, can be left blank
Ping Gateway IP	If selected, this pings the ISP Gateway IP in addition to the target IP(s) If this is enabled, the WAN will only go off-line if both target IPs and the ISP Gateway IP do not respond
TTL (Time To Live)	The max number of hops allowed between the router and the target IP(s) 255 is the least sensitive setting and is recommended where route length is not an issue Range is between 1 and 255 hops
Ping Interval	This defaults to 1 second, it is the amount of time to wait between sending another ping Range is between 1 and 3600 seconds
Ping Retry	The number of times to retry the ping if it fails, it defaults to 10 Ping Retries Range is between 1 and 255 retries

If your router does not show all of these options, the router will use the defaults specified above.

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Advantages:	Disadvantages:
Configurable to meet requirements	Must ping a valid IP address located on the Internet / WAN
Responds quickly to lack of connectivity, around 15 seconds by default	If the remote IP does not respond, for instance the remote site is down, the router could take the WAN interface offline
Can determine whether ISP Gateway is working	Configuring multiple WANs to check connectivity with the same IP could result in multiple WAN interfaces going offline
Can check connectivity to specified remote IPs / locations	Configuring TTL value too low can result in the WAN connection check failing
Can detect Routing issues with the TTL setting	Configuring Ping Interval & Retry values too low can make the Internet connection too sensitive to latency or packet loss
Setting a low Ping Interval with a low Ping Retry count could potentially detect packet loss on a WAN interface

 

Always On

This setting disables the WAN Connection Detection on the router. It is only available for MPoA and Static or Dynamic IP connections, the option will not be visible with PPP connections. When set, the router will only determine WAN state by checking the physical link state, such as whether the network cable is connected or the DSL link is connected.

Advantages:	Disadvantages:
Can be useful in some scenarios where ARP Detect & Ping Detect do not allow the WAN connection to go on-line	Does not check whether the WAN connection has connectivity beyond Ethernet / xDSL link status
	If the WAN has no connectivity, the router will see the connection as on-line
	Failure to detect WAN disconnection could stop Failover or Load Balance from working