with hsrp, routers can give the illusion of a single virtual router to hosts on a lan. this is called a standby group. one router is elected from the group to forward packets that are sent by the hosts; this is the active router. if the active router fails, a standby router will then forward packets in its stead. although there may be more than two routers participating in the group (the virtual router), only the active router at any given time will actually forward packets.
once a router has been elected active, only the active and standby routers send periodic hello packets. of course, if the standby router then fails, another election commences.
routers may belong to more than one standby group, and hellos are kept separate between the groups.
each group has a single well known mac-address and ip address.
hsrp uses the well known mac-address
0000.0c07.acXX
where XX is the group number (ac01 ie. is group 1)
network cisco ccna gns3 certification arteq
a network runs through it
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