D-Link DGS-6600-48TS Configuration Guide - Page 339

Virtual Router Redundancy Protocol (VRRP), Overview, An introduction to VRRP

Page 339 highlights

Volume 4-Layer 3 Configurations / Chapter 32-Virtual Router Redundancy Protocol (VRRP) Chapter Overview Chapter 32 Virtual Router Redundancy Protocol (VRRP) Chapter Overview The following topics are included in this chapter, please go to the topic for more detailed information: • Chapter Overview • An introduction to VRRP • Election of a master router • Behavior of a master router • Behavior of the backup router • Behavior of Initialization state • Critical IP Address • VRRP Configuration Commands • vrrp ip • show vrrp • Configuration Example • VRRP Configuration Example An introduction to VRRP Virtual Router Redundancy Protocol (VRRP) is a redundancy protocol designed to increase the availability of the default gateway servicing hosts on the same subnet. This increased reliability is achieved by advertising a "virtual router" (an abstract representation of master and backup routers acting as a group) as a default gateway to the host(s) instead of one physical router. Two or more physical routers are then configured to stand in for the virtual router, with only one doing the actual routing at any given time. If the current physical router that is routing the data on behalf of the virtual router fails, an arrangement is made for another physical router to automatically replace it. The physical router that is currently forwarding data on behalf of the virtual router is called the master router. Physical routers standing by to take over from the master router in case something goes wrong are called backup routers. Election of a master router Routers have a priority range from 1 to 255 and the router with the highest priority will become the master router and the other routers with a lower priority will then become the backups for the virtual router. The priority of 255 is reserved for the router that is the IP address owner. The IP address owner will always be the master of the virtual router. If there's more than one router that has the same highest priority value; the router with the greatest primary IP address becomes master. The following diagram below shows a simple network with two VRRP routers implementing one virtual router DGS-6600 Configuration Guide 339

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Volume 4-Layer 3 Configurations / Chapter 32-Virtual Router Redundancy Protocol (VRRP)
Chapter Overview
DGS-6600 Configuration Guide
339
Virtual Router Redundancy Protocol (VRRP)
Chapter Overview
The following topics are included in this chapter, please go to the topic for more detailed information:
Chapter Overview
An introduction to VRRP
Election of a master router
Behavior of a master router
Behavior of the backup router
Behavior of Initialization state
Critical IP Address
VRRP Configuration Commands
vrrp ip
show vrrp
Configuration Example
VRRP Configuration Example
An introduction to VRRP
Virtual Router Redundancy Protocol (VRRP) is a redundancy protocol designed to increase the
availability of the default gateway servicing hosts on the same subnet. This increased reliability is
achieved by advertising a “virtual router” (an abstract representation of master and backup routers
acting as a group) as a default gateway to the host(s) instead of one physical router. Two or more
physical routers are then configured to stand in for the virtual router, with only one doing the actual
routing at any given time. If the current physical router that is routing the data on behalf of the virtual
router fails, an arrangement is made for another physical router to automatically replace it. The
physical router that is currently forwarding data on behalf of the virtual router is called the master
router. Physical routers standing by to take over from the master router in case something goes
wrong are called backup routers.
Election of a master router
Routers have a priority range from 1 to 255 and the router with the highest priority will become the
master router and the other routers with a lower priority will then become the backups for the virtual
router. The priority of 255 is reserved for the router that is the IP address owner. The IP address
owner will always be the master of the virtual router.
If there’s more than one router that has the same highest priority value; the router with the greatest
primary IP address becomes master.
The following diagram below shows a simple network with two VRRP routers implementing one
virtual router
Chapter 32