Computer People!

[Ryan1985]

Okay I have a uni test 2mo and have these questions:

Host IP address: 172.20.2.130

Subnet mask: 255.255.255.128

What is the number of subnet bits? (9)

What is the number of host bits? (7)

What is the subnet address for the given host IP address? (172.20.2.128)

What is the broadcast address for this subnet? (172.20.2.255)

I have put the correct answers next to them as we were given them, I just don't know how to arrive at them!

[DaveSR]

Okay I have a uni test 2mo and have these questions:

Host IP address: 172.20.2.130

Subnet mask: 255.255.255.128

What is the number of subnet bits? (9)

What is the number of host bits? (7)

What is the subnet address for the given host IP address? (172.20.2.128)

What is the broadcast address for this subnet? (172.20.2.255)

I have put the correct answers next to them as we were given them, I just don't know how to arrive at them!

←

Subnet mask: 255.255.255.128 (in binary)

a) 11111111.11111111.11111111.10000000

Host IP address: 172.20.2.130

B ) 10101100.10100.10.10000010

a) 11111111.11111111.11111111.10000000

B ) 10101100.00010100.00000010.10000010

-------------------------------------------------

c) 10101100.00010100.00000010.10000000 - subnet mask

Where (1 + 0 = 0, 0 + 0 = 0, 0 + 1 = 0 and 1 + 1 = 1)

a) 11111111.11111111.11111111.10000000

c) 10101100.00010100.00000010.11111101

------------------------------------------------

10101100.000010100.0000001.10000000- 8 bits

B ) 10101100.00010100.00000010.10000010

c) 10101100.00010100.00000010.10000000

------------------------------------------------

10101100.00010100.000000010.1000000 - 8 bits

:censor: :censor: :censor:

Obviously Wrong :ffs: !

But I thought I would leave you with something as it may jog your memory ..... you might have to inverse both at the beggining, I just can't remember as it's too late and it's been a while, but it's something along those line!

If I had a little longer then I probably could do it ....... off for a coffee !

Might as well not have bothered !

[T600]

Okay I have a uni test 2mo and have these questions:

Host IP address: 172.20.2.130

Subnet mask: 255.255.255.128

What is the number of subnet bits? (9)

What is the number of host bits? (7)

What is the subnet address for the given host IP address? (172.20.2.128)

What is the broadcast address for this subnet? (172.20.2.255)

I have put the correct answers next to them as we were given them, I just don't know how to arrive at them!

←

OK, as nobody else has answered, I'll try, though a little rusty on this.

The first question is the tricky one. After that, it's simple.

I would have said the number of subnet mask bits is 25 because the binary representation of 255.255.255.255.128 is

11111111.11111111.11111111.10000000 i.e. 25 1's.

However, the address starting with 172 is a class B address (In the range 128.0.x.x to 191.255.x.x).

In a class B address, the first two pairs of numbers in the Mask must be 255.255. (or 11111111.11111111. in Binary). I presume these two pairs (representing 16 bits) are therefore subtracted from the 25 giving the result of 9 for the number of subnet bits.

After that, it's dead easy. The remaining bits are the host bits i.e. the bits shown as zeros in this binary number.

11111111.11111111.11111111.10000000

which is equivalent to 255.255.255.128

Combine this mask with the host address you were given in the question.

Host IP address: 172.20.2.130

There are thousands of subnets that have the mask shown above, but this network address and the mask tells us that the range of host addresses for this subnet is:-

172.20.2.128 through to 172.20.2.255

If this isn't clear to you then you writing out the above number in binary may help.

The first of these represents all the host bits set to zero and the second all host bits set to 1.

The first number in the subnet always reserved as the network address, and the last number is always the broadcast address. The others can be allocated to network cards.

PS - I see someone else has now replied, but as I've done this now I'm posting it anyway. Hope it helps :D Good luck in your exam.

[sotal]

Sorry couldn't be bothered to fully read the above answers so I might be repeating them but...

The address is a class b ip address so... (to know which class it is look at the first octet - 1-126 is a class A, 128 - 191 is a class B and anything above is a Class C)

If you take the last two sections as Binary you get:

1111 1111 1000 0000

The ones are the subnet bits (so there are 9 - there is your answer dead easy)

The zeros are the host bits (7 another easy answer!)

hope that helps

*edit*

Just to clarify if the address had been a Class A address you would have to look at the last 3 octets to work out how many subnet bits and host bits you had

Class B you look at the last two Octets (as shown above)

Class C you would just look at the last octet

[Jamesb4uk]

I used to be able to do this in my head - but god praise IP calculators :P

J

[Ryan1985]

Thanks for your help guys but I went to see a tutor this morning and he helped me to work them out. In the exam I got a class C address and I reckon I done pretty well maybe only getting 1 or 2 wrong.

In the exam I also had to build a crossover wire and I got 1 end working but the other end just wasn't happening! :(

Also, then had to set up a peer to peer and ping the IP from one to another and I aced that part! :D

[DaveSR]

Thanks for your help guys but I went to see a tutor this morning and he helped me to work them out. In the exam I got a class C address and I reckon I done pretty well maybe only getting 1 or 2 wrong.

In the exam I also had to build a crossover wire and I got 1 end working but the other end just wasn't happening! :(

Also, then had to set up a peer to peer and ping the IP from one to another and I aced that part! :D

←

Buy the cisco book ...... I recommend it !

[sotal]

Thanks for your help guys but I went to see a tutor this morning and he helped me to work them out. In the exam I got a class C address and I reckon I done pretty well maybe only getting 1 or 2 wrong.

In the exam I also had to build a crossover wire and I got 1 end working but the other end just wasn't happening! :(

Also, then had to set up a peer to peer and ping the IP from one to another and I aced that part! :D

←

Buy the cisco book ...... I recommend it !

←

Or Download it