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interview Q

hudda

How many functional IP addresses are available on a /28 network?

my answer was 255.255.255.240 but I have to work on 240, how many network will have I came up 256-240 = 16then I have to continue until I reach 256 and I have got 16 am I right?

Please let me know
Thank you
Hudda

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Comments

royal

/28 = 28 network bits turned on = 4 client bits available = 32 bits used

This means that we do (2^4)-2=14 client ip addresses available

Since /24 is:
11111111.11111111.11111111.00000000

And we're using /28 which means we're borrowing 4 bits from the 4th octet:
11111111.11111111.11111111.11110000

Since it goes 128 64 32 16 8 4 2 1 and we're borrwing the 1st 4, we take 128 + 64 + 32 + 16 = 240.

So yes, you're correct that the subnet mask would be 255.255.240.0. The only difference is we don't use 16 ip addresses, we use 14 client ip addresses. The formula as stated above is (2^amount of bits)-2. When we're working with network bits, it's (2^number of bits). We don't subtract 2 when working with network bits because modern routers will use all 0s and all 1s for the network portion.

seuss_ssues

royal you beat me to it.

but he is correct.

(2^4) - 2 = 14

seuss_ssues

royal wrote:

So yes, you're correct that the subnet mask would be 255.255.240.0

Woops you made a typo there.

Should be 255.255.255.240

Pash

Yep 14, you always lose the subnet and broadcast ip addresses unless otherwise stated...but this is more of a cisco related argument.

How did the rest of the interview go? Best of luck.

Cheers,

royal

seuss_ssues wrote:

royal wrote:

So yes, you're correct that the subnet mask would be 255.255.240.0

Woops you made a typo there.

Should be 255.255.255.240

Good catch. Yep, 255.255.255.240 is what I meant.

binarysoul

It depends whether you use Cisco's ip subnet-zero command or not, so the answer may be 14 or 16. Just my 2 cents...

Do you think you sealed this job for ya?

hudda

How would you boot a computer running the Windows XP operating system that uses NTFS that refuses to boot from the hard drive?

Recently installed a new DVD-R drive, but now the system will not boot up. What are some possible reasons for the problem?

Server 2000 is deployed, it automatically sets workstations to use the server as an internet proxy because you would be expected to use the Proxy Server built into SBS 2000. However, in most installations a NAT router is used instead. Unfortunately, SBS2000 will still occasionally set the workstations to use the server as a proxy, preventing access to the internet Although this can be manually corrected on each workstation by removing the proxy settings in Internet Explorer, what is the best way to fix this issue permanently?

Thanks
Hudda