User`s guide

CONFIGURATION

6.8. VRRP Configuration

To enter the VRRP configuration select the VRRP menu item. VRRP protocol (Virtual

Router Redundancy Protocol) is a technique, by which it is possible to forward routing from

main router to backup router in the case of the main router failure. If the Enable VRRP is

checked, then it is possible to set the following parameters. Parameter Virtual Server IP

Address sets virtual server IP address. This address should be the same for both routers.

A connected device sends its data via this virtual address. Parameter Virtual Server ID

distinguishes one virtual router on the network from others. This implies that the main

and backup routers must use the same value for this parameter. The router, with higher

priority set by the parameter Host Priority, is the main router. According to RFC 2338

the main router has the highest possible priority - 255. The backup router has priority in range

1 – 254 (init value is 100). The priority value equals 0 is not allowed.

It is possible to set Check PPP connection flag in the second part of the window.

The currently active router (either main or backup) will send testing messages to defined

Ping IP Address at periodic time intervals (Ping Interval) with setting time of waiting

for answer (Ping Timeout). The function check PPP connection is used as a supplement

of VRRP standard with the same final result. If there are no answers from remote devices

(Ping IP Address) for a defined number of probes (Ping Probes), then connection is switched

to the other line. It is possible to use for example a DNS server of mobile operator as a test

message (ping) IP address. There's an additional way for evaluating the state of the active

line. It is activated by selecting Enable traffic monitoring parameter. If this parameter is set

and any packet different from ping is sent to the monitored line, then any answer

to this packet is expected for Ping Timeout. If Ping Timeout expires with no answer received

then process of testing the active line continues the same way like in the case of standard

testing process after first test message answer drops out.