Siemens RUGGEDCOM ROX II, User Manual

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Chapter 14
Network Redundancy
RUGGEDCOM ROX II
CLI User Guide
604 VRRP Terminology
Two or more VRRP instances can be assigned to be in the same VRRP Group, in which case, they can failover
together.
An Example of VRRP Groups
In the next example, both host 1 and host 2 use a gateway of 192.168.3.10. The external side can access the
internal side by gateway 192.168.2.10. VRID_20 and VRID_21 are grouped together. Normally, router 1 will
provide both an internal and external access gateway, as its priority is higher than those on Router 2. When
either the internal or external side of Router 1 becomes inoperative, Router 1 will remove give control of both
192.168.2.10 and 192.168.3.10 gateways to Router 2.
192.168.3.2 192.168.3.3
192.168.2.2 192.168.2.3
3
4
6
2
4
5
1
Figure 34: VRRP Group Example
1. Network 2. Remote Router 1 3. Remote Router 2 4. Switch 5. Host 1 6. Host 2
In this example, the remote routers are configured as follows:
Remote Router 1 Remote Router 2
• VRID_20 Gateway IP: 192.168.2.10
• VRID_20 Priority: 100
• VRID_21 Gateway IP: 192.168.3.10
• VRID_21 Priority: 100 • VRID_20 Gateway IP: 192.168.2.10
• VRID_20 Priority: 50
• VRID_21 Gateway IP: 192.168.3.10
• VRID_21 Priority: 50
Other VRRP parameters are the Advertisement Interval and Gratuitous ARP Delay. The advertisement interval is the
time between which advertisements are sent. A backup router will assume the role of Master three advertisement
intervals after the Master fails. If a monitored interface goes down, a Master router will immediately signal an
election and allow a Backup router to assume the Master roles.
The router issues a set of gratuitous ARPs when moving between Master and Backup roles. These unsolicited ARPs
teach the hosts and switches in the network of the current MAC address and port associated with the gateway.
The router will issue a second set of ARPs after the time specified by the Gratuitous ARP delay.