X. WAN

WAN Connection Detection

Products:
Vigor 2620Ln
Vigor 2760
Vigor 2762
Vigor 2765
Show all

Keywords:
ARP Detect
ARP Detection
Disconnection
Fail Over
Show all

DrayTek Vigor routers have the ability to ensure an Internet connection is in a working state with WAN Connection Detection. This checks the Internet connection for connectivity and if that fails, drops the WAN connection to restart it or use a Failover Backup connection.

It is possible for an Internet connection to remain active but be in a state where it cannot communicate with the Internet.
For instance where an ISP has routing issues that stops access to the Internet, the link between the router and the ISP would still be active. The router would not see a need to stop using that WAN interface and switch to a Backup WAN, because it can still contact the ISP Gateway.

In this scenario, Ping Detection should be used to force the router to check connectivity beyond the ISP with a target remote IP; if it's unable to ping, the router will drop that Internet connection until it can get a response from that IP again.


The DrayTek Vigor routers have 3 types of configurable WAN Connection Detection available:

ARP Detection Sends an ARP request packet to the WAN Gateway, if there is no response within 30 seconds, the router will drop the WAN connection
Ping Detection Sends an ICMP ping packet to the specified IP address(es) and if those addresses do not respond after the configured number of retries, the router will drop the WAN connection
Always On This disables the WAN Connection Detection and limits detection to Physical Link connectivity only. This option is only available for Static IP & DHCP connections

PPP connections such as PPPoA and PPPoE Internet connections, have an inherent form of link detection called LCP (Link Control Protocol). LCP will drop the PPP connection if the PPP server and Vigor router are unable to communicate using this protocol, the router will allow 3 retries before dropping the connection with an "LCP Timeout".


This table outlines the potential benefits to using the specific WAN Connection Detection methods:

Connection IssueAlways OnARP DetectionPing Detection
Ethernet link disconnection tick tick tick
ADSL / VDSL link disconnection tick tick tick
PPPoE / PPPoA disconnection   tick tick
Connectivity with ISP Gateway   tick tick
Loss of IP Connectivity     tick
Connectivity to specific IPs / Web sites     tick
Significant Packet Loss     tick
Too many hops (TTL)     tick

Setup & More Information

These settings are configured from the WAN interface settings in [WAN] > [Internet Access] > WAN Details Page for each WAN connection:

WAN Connection Detection methods can be set for all WAN interfaces individually on the router.

Please Note: Some settings shown may not be available on all DrayTek routers or firmware versions. Updating to the latest firmware (currently 3.8.2.3) may provide more configuration options.

ARP Detect

ARP Detection is the default WAN Connection Detection mode on all DrayTek Vigor routers that run DrayOS.

This is designed to check connectivity to the ISP by testing whether the ISP Gateway address gives a response to an ARP request.

The router sends this ARP request every 5 seconds and if there is no response from the ISP Gateway within 30 seconds, the DrayTek router will drop the WAN interface until it begins to receive ARP responses again.

This can be used with all types of WAN interface.

Advantages:
No configuration required
Responds quickly to lack of connectivity, ~30-40 seconds
Can determine whether ISP Gateway is working

 

Disadvantages:
Cannot determine whether connection is working beyond the ISP Gateway

How do you rate this article?

1 1 1 1 1 1 1 1 1 1