Exam tip

SephStorm

Does anyone have any tips for eliminating incorrect answers on Cisco exams? my concern isnt with general info, but when a question requires subnetting, I can get the answer for 1 or 2 IP addresses, but subnetting 4-5 networks to determine IF it is even a problem with IP addresses seems counterproductive. Any ideas?

steveyeung

use the magic number, the rightmost bit of the network part! which can help you to determine the network range,
and thus eliminate some answers quickly.
0 0 0 0 0 0 0 0
128 64 32 16 8 4 2 1 <- magic numbers

eg.
Which two subnetworks would be included in the summarized address of 172.31.80.0/20? (Choose two)
A. 172.31.17.4/30
B. 172.31.51.16 /30
C. 172.31.64.0/18
D. 172.31.80.0/22
E. 172.31.92.0/22
F. 172.31.192.0/18

172.31.80.0/20 = 172.31.0101|0000.0 (so the magic number is 16)
so the range of valid network address is between
172.31.80.0 ~ 172.31.95.255 (because 172.31.96.0 is the start of the next network address)
from here, you can already eliminate the answers ABCF

smcclenaghan

This isn't what you're asking, so sorry for that, but I strongly recommend you burn a few days here:
subnettingquestions.com - Free Subnetting Questions and Answers Randomly Generated Online

and get used to subnetting within a few seconds.

The reason I say that is that it's just integrated into too many questions. Being slow at it is going to kill you.

As for eliminating wrong answers. If that's the route you go, look at the answers and rule out the quick ones first. For example, if something asks "Why isn't A peering with B on OSPF" and the answers are:
a) Area on A and B don't match.
b) Subnet on A and B don't match.
c) Hello timers don't match.
d) se0/0 on A is down
e) The process ID doesn't match.

You should be able to rule out E immediately and A & C at a glance, and D in a few seconds. B will take the longest and you might find the correct answer before you have to get there.

Ismaeljrp

It sounds like your subnetting skills are slow. Get faster and you shouldn't have a problem. With those types of questions. Try looking up other people's topologies and analyze the addressing scheme. subnettingquestions are really good too. Subnettingisfun helped me a lot with speed, get to around 20 seconds average and you should be good. You'll actually be faster than that, but depending how fast you type it could take you more or less.

SephStorm

my problem is I dont like those magic number methods, or those questions. What I do is write the chart at the beginning of the exam, 128-2/ cidr chart below that, and SM below that. Convert the mask to binary and build the networks. no other steps. Its the easiest way to get a correct answer, but it doesnt answer for hosts or networks or any of those other questions you find on those sites, but then again, ive never encountered those questions on the exam.

But your method may have merit in that if I can convert all the masks quickly, I might be able to detect a problem right away.

Any issues with my method? The reason I dont like the others, too many steps, and I get confused with what I do when...

goldenlight

Magic Number trick is definitely the way to go. Google Dans videos.

Once you make your subnetting chart then you count in multiples. I made this chart while cisco tutorial was going. I believe the tutorial was 15 minutes

example
0,128,255
0,64,128,192,255
0,32,64,96,128,160,192,224,255
0,16,32,48,64,80,96,112,128,144,160,176,192, 208, 224, 240 ,255
0,8
0,4 just devided these numbers
0,2 All even numbers.

SephStorm

that requires a lot of math, which well, doesnt work with me.

sucanushie

Write down your powers of 2 when you sit for the exam.

2
4
8
16
32
64
128
256
512
1024
2048
....

thendif if the question says you need 40 host count down your list 64 gives you your 40 so you need 6 host bits.

[URL="tel:11000000 /26"]11000000 /26[/URL]

and do the reverse for networks. Say you need 25 networks. You need 5 network bits.

[URL="tel:11111000 /29"]11111000 /29[/URL]

then you can see you have 3 host bits 2 to the power of 3 is 8. 8-2 =6 usable host.