Field
Description
first address. VRRP advertisements are always sent with the
primary IP address as source of the IP packet.”
VRRP Advertisement
A keepalive that sends the master to the backup gateway to in-
dicate his reachability.
Virtual Router Master
“The VRRP router that takes over forwarding the packets that
have been sent to the IP addresses associated with the “virtual
router”. It is also responsible for answering ARP (Address Res-
olution Protocol) requests for these IP addresses."
Virtual Router Backup
“The group of VRRP routers that take over responsibility for for-
warding the packets if the master fails.” In backup status these
VRRP routers are inactive, i.e. they do not respond to any ARP
requests."
21.12.1 Virtual Routers
When using a route redundancy protocol, multiple routers are combined into a logical unit.
The router redundancy protocol BRRP manages the routes involved and organises these
as follows:
It ensures that only one routers within the logical connection is active.
It guarantees that if the active route fails, another router takes over the function of the failed
device. The time that each router is active is determined by the priority assigned to the
router.
Let us take the example of a simple scenario, in which gateway A provides Internet access
for the hosts in a LAN. If this gateway fails, all hosts cannot access the Internet and their
routes are configured statically. To allow the hosts continued access to the Internet, gate-
way B offers all hosts in the LAN the service that gateway A previously performed. All the
tasks of a “virtual router” and the switching of services from one gateway to the other are
controlled by the BRRP redundancy procedure.
The BRRP conforms to the specifications in RFC 2338 and the relevant Internet draft (see
www.ietf.org
).
The configuration of the router redundancy procedure is carried out in the following steps:
• Configuration of the interface via which the BRRP advertisement data packets are sent.
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