Analysis of broadcasting

Onea few specialIpAddress

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, there are four special broadcast addresses in the lower part of the table. are limited broadcast addresses, broadcasts to networks, broadcasts to subnets, broadcasts to all subnets, respectively. Because of its concept, and the corresponding subnet mask of the concept of understanding is not very thorough, this analysis has given me a lot of help.

Oneexperience these four kinds of broadcasts

take network address as 142.1.2.3 as an example

①             If the mask is255.255.128.0

we can be informed in the all subnets for IP are 142.1.0.0,142.1.128.0.

Therefore, the broadcast address of this address is 142.1.127.255, and 142.1.255.255 This broadcast address in this case is only a broadcast address to the 142.1.128.0 network segment.

The number of hosts for this network segment is 2^15-2 . The totalnumber of hosts for the entire Network segment (142.1.x.x) is(2^15-2)

Ii             If the mask is255.255.255.0

we can be informed in the The IP subnet is 142.1.2.0, and the broadcast address is 142.1.2.255.

Notice that the 142.1.255.255 at this point is a broadcast address that points to all subnets.

number of hosts is 2^8-2

③             If the mask is255.255.255.128

therefore in the the subnet under IP is 142.1.2.0, and the broadcast address is 142.1.2.127.

note the broadcast address at this point:142.1.255.255 is a broadcast to the network.

number of hosts is 126(2^7-2)

TwoAnalysis of the sameIpchanges in the number of hosts under different masks

in a B, the class address, still take 142.1.2.3 as an example, explore /16 and /17 These two kinds of masks, bring the number of host changes.

/16: The number of hosts on the subnet is 2^16-2and the total number of hosts is 2^16-2=65534

/17: The number of subnets is 2^15-2, the total number of hosts is (2^15-2) =65532

obviously not a multiple relationship. From this number can be known that the reason why 2 fewer hosts is because of a network number 142.1.128.0 and broadcast address 142.1.127.255.

ThreeOffal

In the discussion with many old network workers to find a problem, irrelevant. Their concept of the network, the network number is not the same as the theoretical books, we talked for a long time before we found two people, not a thing to say. Such as:

After introducing subnetting concepts

network Block =(< network number >,< subnet number >,< host number >) (1)

After the introduction of the subnet mask concept

         Network block = ( < network number > host number >)                                                                 (2)

Although the subnet number of the formula (1) is separated from the host number, in the formula (2) < network number >=< type (1)< Network number >+ type ①< subnet number >>

So, after discussing with the teachers and the net workers, I have to make it clear that the network number, the network

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Analysis of broadcasting