Draytek VIGOR2925 SERIES User Manual page 396

Available settings are explained as follows:
Item
Enable High Abailablity
Redundancy Method
Vigor2925 Series User's Guide
Description
Check this box to enable HA function.
Choose Hot-Standby or Active-Standby as the method for
HA.
Hot-Standby -
Such method is suitable for a user which has one ISP
account. With such method;

All WANs of secondary routers will be shut down by
HA function.

WAN settings of primary and secondary routers can
be the same.
Note: When Hot-Standby is used, wireless LAN will
be "enabled" automatically for clients connecting to
the primary router; however, wireless LAN on
secondary router will be "disabled" directlly. Thus
clients can not connect to the secondary router any
more.
Active-Standby -
Such method is suitable for a user which has multiple ISP
accounts. With such method;

All WANs of secondary routers can be up. Therefore,
the user can route it's traffic to secondary.

WAN settings of primary and secondary routers must
not be the same.

The Config Sync must be disabled, or you cannot
change redundancy method to active-standby.
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