Extreme Networks ExtremeWare XOS 11.3, Руководство пользователя

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ExtremeWare XOS 11.3 Concepts Guide
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22 Virtual Router Redundancy Protocol
This chapter covers the following topics:
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Overview on page 485
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Determining the VRRP Master on page 485
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Additional VRRP Highlights on page 488
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VRRP Operation on page 489
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VRRP Configuration Parameters on page 491
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VRRP Examples on page 492
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VRRP Cautions on page 494
This chapter assumes that you are already familiar with the Virtual Router Redundancy Protocol
(VRRP). If not, refer to the following publications for additional information:
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RFC 2338— Virtual Router Redundancy Protocol (VRRP)
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RFC 2787— Definitions of Managed Objects for the Virtual Router Redundancy Protocol
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Draft IETF VRRP Specification v2.06
Overview
Like the Extreme Standby Router Protocol (ESRP), VRRP allows multiple switches to provide redundant
routing services to users. VRRP is used to eliminate the single point of failure associated with manually
configuring a default gateway address on each host in a network. Without using VRRP, if the
configured default gateway fails, you must reconfigure each host on the network to use a different
router as the default gateway. VRRP provides a redundant path for the hosts. Using VRRP, if the default
gateway fails, the backup router assumes forwarding responsibilities.
Determining the VRRP Master
The VRRP master is determined by the following factors:
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VRRP priority—This is a user-defined field. The range of the priority value is 1 to 254; a higher
number has higher priority. The value of 255 is reserved for a router that is configured with the
virtual router IP address. A value of 0 is reserved for the master router, to indicate it is releasing
responsibility for the virtual router. The default value is 100.
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Higher IP address—If the routers have the same configured priority, the router with the higher IP
address becomes the master.