Subnetting Speed

tr1x

I can finally subnet (well, mostly), I don't think I'm particularly fast though. How fast do you need to be for the CCENT? What were your strategies to do it faster? I find that if I write down 128 64 32 16 8 4 2 1 on a piece of paper it helps me to calculate stuff a bit faster. Is that bad, though? Do I need to be able to do it entirely in my head without writing anything down?

antohesorin

Well i wrote it on the piece of paper they gave me when i took my CCENT exam just before the exam start, there will be a 15 minutes exam tutorial just before you can start the exam, you have plenty of time to write stuff down that will help you.

Regards
Sorin

tr1x

Oh great, that's good to know. How much did you actually use the paper during the test? Did you mostly just calculate everything in your head? How much did you use your calculator (you can use the basic Microsoft one during the rest, right?)

Futura

tr1x wrote: »

I can finally subnet (well, mostly), I don't think I'm particularly fast though. How fast do you need to be for the CCENT? What were your strategies to do it faster? I find that if I write down 128 64 32 16 8 4 2 1 on a piece of paper it helps me to calculate stuff a bit faster. Is that bad, though? Do I need to be able to do it entirely in my head without writing anything down?

You won't need to work it out with bits of paper, its like driving in my opinion, do it enough and you'll just see the answers.

have a break from it every so often and reflect. this worked for me.

Once you have it down, its one less thing to worry about and you know you've got some guaranteed points by subnetting. questions are a lottery but you know theres going to be some subnetting questions.

good luck

antohesorin

tr1x wrote: »

Oh great, that's good to know. How much did you actually use the paper during the test? Did you mostly just calculate everything in your head? How much did you use your calculator (you can use the basic Microsoft one during the rest, right?)

I didn't use it much since most subnets where easy to do but i did use it for some class b subneting. As for the calculator, i saw no such thing but that said i didn't even need it. I agree with Futura, if you do enough tests you will just fly over the subnets questions.

Regards
Sorin

NetworkVeteran

tr1x wrote: »

I can finally subnet (well, mostly), I don't think I'm particularly fast though. How fast do you need to be for the CCENT?

I think people overblow this. Let's see...

Q. You're assigned 10.1.1.0/24. You want to find a subnet mask that provides as many subnets as possible that allows at least ten devices per subnet. What's the mask and the first few subnet numbers?

A. You need 4 subnet bits (2^n - 2 > 10, min n = 4). Therefore, you want a /28 mask (32-4=2 and we count by 16s (2^4=16). 10.1.1.0, 10.1.1.16, 10.1.1.32...

Hm. It took me 5 seconds to solve, 60s to write out and explain it. I'd say aim to solve it within 30-60s. That's fine for exam constraints, and more than a minute would look bad in an interview.

You should be able to grasp /8, /16, /24, and /32 immediately of course.

What were your strategies to do it faster?

Practice, young Padawan.

I find that if I write down 128 64 32 16 8 4 2 1 on a piece of paper it helps me to calculate stuff a bit faster. Is that bad, though?

That's fine. Even for an experienced guy at an interview. Double-checking your work is wise!

poojajoshi

Assuming a Subnet mask of 255.255.248.0,three of d following addresses are valid host addresses.Which are these addresses?(choose 3)
1)172.16.9.0
2)172.16.8.0
3)172.16.31.0
4)172.16.20.0

sratakhin

You passed CCNA yet you can't figure it out? The right answers are 1, 3 and 4. 172.16.8.0 is a subnet.

elderkai

No, you are definitely not allowed to use a calculator during the exam.

NetworkVeteran

1)172.16.9.0
3)172.16.31.0
4)172.16.20.0

I wouldn't use any of those as host addresses. They are too likely to introduce confusion. Using these would be a case of book-smart but not street-smart.

mguy

What elderkai said, not allowed to use calculator.

CCNA tests "applied" subnetting skills in the form of VLSMs and network summarization. You must ascertain to bounds of the networks.

sratakhin

2 NetworkVeteran: would you use something like 172.16.9.255 or does the same logic apply?

NetworkVeteran

sratakhin wrote: »

2 NetworkVeteran: would you use something like 172.16.9.255 or does the same logic apply?

I would generally avoid addresses ending in both .0 and .255 as host addresses, because I have seen first-hand the confusion unexpected addresses can cause even experienced engineers. With private addresses such as in the example, you can almost always afford that small bit of waste.

I've even seen confusion when using the all-zeores and all-ones subnets, but that's less common, and enough addresses are involved that using them sometimes can't be avoided.

poojajoshi

i got Ans. but little bit confusion abt 172.16.8.0 network..
i'm not passed CCNA just learning (exam preparation)

thankx for give me reply to thread...!!!!