User`s manual

EDR-G903/G902 Features and Functions
3-23
Network Redundancy
Moxa EtherDevice Router provides 2 types of network redundancy functions: WAN backup (EDR-G903 only)
and VRRP. The EtherDevice Router has two WAN interfaces: WAN1 is the primary WAN interface and WAN2 is
the backup interface. When the EtherDevice Router detects that connection WAN1 has failed (Link down or Ping
fails), it will switch the communication path from WAN1 to WAN2 automatically. When WAN1 recovers, the
major communication path will return to WAN1.
WAN Backup (EDR-G903 only)
How Dual WAN Backup Works
A power utility at a field site connects to a central office via two different ISPs (Internet Service Providers).
ISP-A uses Ethernet and ISP-B uses satellite for data transmission, with Ethernet used as the major connection
and the satellite as the backup connection. This makes sense since the cost of transmitting through the satellite
is greater than the cost of transmitting over the Ethernet. Traditional solutions would use two routers to
connect to the different ISPs. In this case, if the connection to the primary ISP fails, the connection must be
switched to the backup ISP manually.
The EtherDevice Router’s WAN backup function checks the link status and the connection integrity between the
EtherDevice Router and the ISP or central office. When the primary WAN interface fails, it will switch to the
backup WAN automatically to keep the connection alive.
When configuring the EtherDevice Router, choose one of the two following conditions to activate the backup
path:
• Link Check: WAN1 link down
• Ping Check: Sends ping commands to a specific IP address (e.g., the IP address of the ISP’s server) from
WAN1 based on user configurable Time Interval, Retry, and Timeout.
When the WAN backup function is enabled and the Link Check or Ping Check for the WAN1 interface fails, the
backup interface (WAN2) will be enabled as the primary interface.
WAN Backup Configuration
Select Backup for the WAN2/DMZ Connect Mode, and then go to the Network Redundancy  WAN Backup
setting page for the WAN Backup configuration.