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JunosE 11.3.x Service Availability Configuration Guide
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VRRP Platform Considerations
150
In case of a failure, VRRP dynamically shifts the packet-forwarding responsibility to a
backup router. VRRP creates a redundancy scheme that enables hosts to keep a single
IP address for the default gateway but maps the IP address to a well-known virtual MAC
address. VRRP provides this redundancy without user intervention or additional
configuration at the end hosts.
The advantage of using VRRP is that you gain a higher availability for the default path
without requiring configuration of dynamic routing or router discovery protocols on every
end host.
VRRP routers viewed as a redundancy group share the responsibility for forwarding packets
as if they owned the IP address corresponding to the default gateway configured on the
hosts. At any time, one of the VRRP routers acts as the master, and other VRRP routers
act as backup routers. If the master router fails, a backup router becomes the new master.
In this way, router redundancy is always provided, allowing traffic on the LAN to be routed
without relying on a single router.
A master always exists for the shared IP address. If the master goes down, the remaining
VRRP routers elect a new master VRRP router. The new master forwards packets on
behalf of the owner by taking over the virtual MAC address used by the owner.
When implemented in your network, VRRP interprets any active link to a subnet to indicate
the router has access to the entire subnet. VRRP leverages the broadcast capabilities of
Ethernet. Provided that one of the routers in a VRRP configuration is running, ARP requests
for the IP addresses assigned to the default gateway always receive replies. Additionally,
end hosts can send packets outside their subnet without interruption.
VRRP Implementation in E Series Routers on page 152
VRRP Router Election Rules on page 152
Before You Configure VRRP on page 156
Configuring VRRP on page 157
For information about modules that support VRRP on ERX14xx models, ERX7xx models,
and the ERX310 Broadband Services Router:
See ERX Module Guide, Table 1, Module Combinations for detailed module specifications.
See ERX Module Guide, Appendix A, Module Protocol Support for information about the
modules that support VRRP.
For information about modules that support VRRP on the E120 and E320 Broadband
Services Routers:
See E120 and E320 Module Guide, Table 1, Modules and IOAs for detailed module
specifications.
See E120 and E320 Module Guide, Appendix A, IOA Protocol Support for information
about the modules that support VRRP.
Copyright © 2010, Juniper Networks, Inc.
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