what is unicast address

alt.certification.ciscoGiven the choices below, which address
represents a unicast address?
A. 224.1.5.2
B. FFFF. FFFF. FFFF.
C. 192.168.24.59/30
D. 255.255.255.255
E. 172.31.128.255/18
I know the right answer is 'E',while I want to know sth about unicast
address.
Reply to
leeloo.au
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An unicast address corresponds to a single interface on a single host, while a multicast address can correspond to multiple hosts. Unicast addresses range goes from 0.0.0.0 to 223.255.255.255, but of course not all of them are usable. What do you want to know?
Reply to
pk
A unicast is simply an address that points to one particular host, as opposed to multiple, or even all, hosts like a multicast or broadcast. Here is how your list breaks down:
Since the first octet of this address is 224 it falls in the multicast range so it is not a unicast address.
This is the target MAC address of a broadcast, so again, not a unicast.
This one is here to trick you. If you work out the subnet it is 192.168.24.56 through 192.168.24.59. Since 192.168.24.59 is the last IP in the range, it is the broadcast address. In binary, all the host bits are ones. So this address actually referes to all of the hosts in the subnet and not just one.
This represents a broadcast address sent to anyone who is listening on a shared network segment.
Again, if we work out the subnet here the range includes 172.31.128.0 through 172.31.191.255. Since 172.31.128.255 falls in between those two numbers, it is a host IP. In other words, it referes to one particular host, making it a unicast address.
Hope that helps,
Joseph
Reply to
Joseph Stalin
thanks all of you,i think i get what i need!
Reply to
leeloo.au

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