User`s guide

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VRRP (Virtual Router Redundancy Protocol) allows multiple physical routers to appear as a
single gateway for IP communications in order to provide back-up WAN communications in
the event that the primary router in the group fails in some way. It works by allowing
multiple routers to monitor data on the same IP address. One router is designated as the
“Master” of the address and under normal circumstances it will route data as usual.
However, the VRRP protocol allows the other routers in the VRRP group to monitor the
“Master” and if, they detect that it is no longer operating, negotiate with each other to take
over the role as owner. The protocol also facilitates the automatic re-prioritization of the
original owner when it returns to operation.
Enable VRRP on this interface
This parameter enables VRRP on this interface.
VRRP Group ID
The VRRP group ID parameter is used to identify routers that are configured to operate
within the same VRRP group. The default value is 0 which means that VRRP is disabled on
this Ethernet interface. The value may be set to a number from 1 to 255 to enable VRRP
and include this Ethernet port in the specified VRRP group.
VRRP Priority
This parameter is used to set the priority level of this Ethernet interface within the VRRP
group from 0 to 255. 255 is the highest priority and setting the priority to this value would
designate this Ethernet interface as the initial “Master” within the group. The value selected
for the VRRP priority should reflect the values selected for other routers within the VRRP
group, i.e. no two routers in the group should be initialized with the same value.
Boost the priority by n for s seconds after switching to the MASTER state
Increases the VRRP priority by the specified amount for the specified amount of time when
the router has become the VRRP group master. The reason for why you might want to do
this is to provide some network stability if the original Master keeps going on and off line
thus causing a lot of VRRP state switches.
Enable VRRP+ Probing
This parameter enables VRRP+ probing on this Ethernet interface.
VRRP with probing differs from standard VRRP in that it dynamically adjusts the VRRP
priority of an interface and if necessary, changes the status of that interface from “master”
to “backup” or vice-versa. It does this by “probing” an interface, either by sending an ICMP
echo request (PING) or by attempting to open a TCP socket to the specified Probe IP
address. Hence VRRP operation is enhanced to ensure that a secondary router can take over
under a wider range of circumstances.
Send p probe to IP address a.b.c.d TCP port n
Configures VRRP+ to send a probe packet to desired IP address and TCP port. The TCP port
is needed if the probe type is TCP.
The routing code is used to determine which interface should be used. This allows the unit
to test other interfaces and adjust the VRRP priority according to the status of that
interface. For example, the user may wish to configure probing in such a way that the Digi
router WAN interface is tested, and adjust the VRRP priority down if the WAN is not
operational. Another example would be to probe the WAN interface of another VRRP router,
and adjust the local VRRP priority up if that WAN interface isn’t operational. When
configured to probe in this manner, it is necessary to configure a second Ethernet interface
to be on the same subnet as the VRRP interface. This is because the VRRP interface cannot
be used when it is in backup mode. The probes should be sent on this second interface. The
second interface will have the other VRRP router as its gateway. The routing table should be
configured to direct packets for the probe address to the desired interface.