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Community Member

subnetting exam question

Hi guys, just wondering if someone could correct my answer (not 100% sure I am correct) please

question:

  • GreenEnergy Ltd has been allocated the IP address 199.199.1.0/24 by their ISP. The network administrator for GreenEnergy Ltd.  has decided to split this address space into 16 subnetworks. For this subnetting arrangement, calculate the subnet mask, the valid host range and the broadcast address for the second subnet. Show the workings of your calculations.

(12 marks)

my answer:

original subnet mask = 255.255.255.0

# of subnets: 2(5) = 32 subnets

# hosts: 2(3) -2 = 6 on each subnet

new subnet mask = 255.255.255.248

subnet#networkrangebroadcast
0199.199.1.0199.199.1.1 - 199.199.1.6199.199.1.7
1199.199.1.8199.199.1.9 - 199.199.1.14199.199.1.15
2199.199.1.16199.199.1.17 - 199.199.1.22199.199.1.23

....

....

..31   

so to answer the question fully:

subnet mask: 255.255.255.248

valid host rage for second subnet (subnet# 1): 199.199.1.9 - 199.199.1.14

boradcast address for second subnet (subnet# 1): 199.199.1.15

Thanks in advance =)             

1 ACCEPTED SOLUTION

Accepted Solutions
Purple

subnetting exam question

Hi,

if you need 16 subnets then you will need 4 bits for the subnet so you'll have 24 for the network and 4 more for the subnet which makes a /28 = 255.255.255.240

so the first subnet will be 199.199.1.0/28 and the second one will be 199.199.1.16/28 so valid host range is 199.199.1.17-199.199.1.30 and the broadcast address is 199.199.1.31

Regards

Alain

Don't forget to rate helpful posts.

Don't forget to rate helpful posts.
8 REPLIES
Purple

subnetting exam question

Hi,

if you need 16 subnets then you will need 4 bits for the subnet so you'll have 24 for the network and 4 more for the subnet which makes a /28 = 255.255.255.240

so the first subnet will be 199.199.1.0/28 and the second one will be 199.199.1.16/28 so valid host range is 199.199.1.17-199.199.1.30 and the broadcast address is 199.199.1.31

Regards

Alain

Don't forget to rate helpful posts.

Don't forget to rate helpful posts.
Community Member

subnetting exam question

thank you very much

Cisco Employee

subnetting exam question

Craig,

A /24 has 256 addresses. If you subdivide as indicated, you get 16 subnets with 16 addresses each.

subnet mask: 255.255.255.240

subnet 0: 199.199.1.0/28 range 199.199.1.1 - 199.199.1.14 broadcast 199.199.1.15

subnet 1: 199.199.1.16/28 range 199.199.1.17 - 199.199.1.30 broadcast 199.199.1.31

...

subnet 15: 199.199.1.240/28 range 199.199.1.241 -199.199.1.254 broadcast 199.199.1.255

Regards

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
Community Member

subnetting exam question

cheers guys, both great answers

Community Member

Re: subnetting exam question

so just to make sure i understand subnetting now, i have completed another question. hopefully i got this one correct

  • Tamhlacht Communications Ltd., has been allocated the IP address

192.0.1.0/24 by their ISP. The network administrator for Tamhlacht

Communications Ltd. has decided to split this address space into 4

subnetworks. For this subnetting arrangement, calculate the subnet

network address, the valid host range and the broadcast address for

the each subnet. Show the workings of your calculations.

(14 marks)

new subnet mask: 255.255.255.192

subnetnetworkrangebroadcast
0192.0.1.0192.0.1.1 - 192.0.1.62192.0.1.63
1192.0.1.64

192.0.1.65 - 192.0.1.126

192.0.1.127
2192.0.1.128

192.0.1.129 - 192.0.1.190

192.0.1.191
3192.0.1.192

192.0.1.193 - 192.0.1.254

192.0.1.255

thanks again guys

Cisco Employee

Re: subnetting exam question

Hi Craig,

You are correct.

Regards

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
Community Member

Re: subnetting exam question

Hi again guys, sorry to bump this post but i have 1 last question that i want to make sure is correct, before my exam tomorrow..

this one if different for me because the company does not want a number which of i used to doing like 1, 2, 4, 8, 16... subnetworks they want a number in between (6 on this occasion)

http://gyazo.com/1258864a39c63c2852c901f577d8b7a7.png

my answer so far:

since they want 6 subnets, i must take 4 bits from the subnet which will give 32 hosts per subnet and a subnet mask off 255.255.255.224

subnet#networkrangebroadcast
0200.200.10.0200.200.10.1 - 200.200.10.30200.200.10.31
1200.200.10.32200.200.10.33 - 200.200.10.62

200.200.10.63

..

..

6

200.200.10.160

200.200.10.161 - 200.200.10.190200.200.10.191

is this answer correct? are my ranges and broadcast addresses correct?

Community Member

Re: subnetting exam question

can anyone tell me if the above question is correct please? exam tomorrow

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