Westermo MR Series - Manual (Page 95)

95 6622-3201
Web Interface and Command Line Reference Guide www.westermo.com
Confi gure > Ethernet > ETH n > VRRP Probing 4.27
The VRRP parameters at the bottom of the Configure > Ethernet pages are used to configure the
router to participate in a standard VRRP group. The parameters on the VRRP Probing pages are
used to enable and configure an enhanced version of VRRP.
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.
Before configuring the unit to use VRRP Probing, first configure the Group ID and Group priority
parameters on the Configure > Ethernet page as appropriate. Then use the following parameters to
set up probing.
Using the Web Page(s)
Probe mode:
This parameter is used to enable or disable VRRP probe mode. When set to “Off”, VRRP prob-
ing is disabled. When set to “TCP”, the unit will “probe” the specified interface by attempting to
open a TCP socket. When set to “ICMP” it will probe by sending ICMP echo requests (PINGs).
Backup state probe interval (s):
When probing is enabled, this parameter specifies the interval in seconds between successive
probe attempts when the interface is in VRRP backup mode.
Master state probe interval (s):
When probing is enabled, this parameter specifies the interval in seconds between successive
probe attempts when the interface is in VRRP master mode.
Probe failure limit: This parameter specifies the number of probe failures that must occur before
the Probe failure priority adjustment is applied to the Group priority value. If this happens the
Probe failure limit is only reset to 0 after the value specified by Consecutive probe successes
required is reached.
Consecutive probe successes required:
This many consecutive successful probes are required before the current failure count is reset
to 0.
Probe IP address:
This is the IP address to which probes are issued. Note that the normal 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 con figure probing in such a way that the Westermo 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 opera tional. 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.
Probe port: This parameter specifies the TCP port number to use when Probe mode is set to
TCP.