# need help with subnetting question

Inactive Imported Users Posts: 167
Hello PPl,

My intro exam is near and I'm worried about my subnetting, actually I'm still confuse can you help me and explain to me clearly. I know how to calculate the subnet and broadcast but the thing is when I got question like this I totally lost!!!!!.

Which of the following IP addresses would not be in the same subnet as 190.4.80.80, mask 255.255.240.0?
a.190.4.80.1
b.190.4.80.50
c.190.4.80.100
d.190.4.80.200
e.190.4.90.1f.10.1.1

My answer in this question is it is a class B which gives me 128-191
I subtructed 256-240 gives me 16 which is the starting subnet.
now 16 32 48 64 80 96 112 etc... so on, I know that it is in subnet 80 because of 192.4.80.0, the broadcast of this is 95 since 96 is the next subnet am I right?

so the valid IP is 81 - 94
so what is the answer in this question since it's asking me which of the ff. IP is ? or am I totally lost?

However, the mask of this is diff. which gives me 255.255.255.128
in class B the mask is 255.255.0.0 so it uses the 3rd octet and the 4th octet. Now applying the above calculation would be diff. since it uses both the 3rd and 4th octet now can you help me extracting this and solve this problem. I know guys you can do this for me it is diff.
My exam is near and I wish I could pass it.

Which of the following IP addresses would not be in the same subnet as 190.4.80.80, mask 255.255.255.128?
a.190.4.80.1
b.190.4.80.50
c.190.4.80.100
d.190.4.80.200
e.190.4.90.1f.10.1.1.1

Thanks for all the help and advice you will share in this question

Chinaman

• Member Posts: 195
is option E in both questions correct?

e.190.4.90.1f.10.1.1
• Member Posts: 34 ■■□□□□□□□□
For your last question, it is quite easy. Since you have the .128, that would mean you can only have .0 and .128 for the last octet. Just remeber for this mask, anything on the last octet below 128 is in the .0 subnet and any number above 128 is on the 128 subnet.

Since your question is asking which is NOT in same subnet as 192.168.80.80, the last octet will show you that it is below 128 so anything above 128 in the last octet is not on the same subnet.

From your options, that would be D, E, and F.[/quote]
“Remember that everyone you meet is afraid of something, loves something, and has lost something”
• Member Posts: 34 ■■□□□□□□□□
For your first question. the mask 255.255.240.0, the 3rd octet will tell you that you will have subnets in blocks of 16.

Since it is asking about hosts in the same subnet as 190.4.80.80, it is asking about hosts that fall in the 190.4.80.0 subnet. the next subnet after this will be 190.4.96.0. Knowing the next subnet will help you determine the broadcast address, which would be 190.4.95.255. So anything from the subnet to the broadcast address are the available hosts.

You can assign hosts starting from 190.4.80.1 up to 190.4.95.254, from your options, that would be all of them except option f.
“Remember that everyone you meet is afraid of something, loves something, and has lost something”
• Member Posts: 195
myk_roque wrote:
You can assign hosts starting from 190.4.80.1 up to 190.4.95.254, from your options, that would be all of them except option f.

O is ah option F that there
• Member Posts: 34 ■■□□□□□□□□
Jiggsaww wrote:
myk_roque wrote:
You can assign hosts starting from 190.4.80.1 up to 190.4.95.254, from your options, that would be all of them except option f.

O is ah option F that there

Yah,.. I got confused at first glance there. Initially I thought it was a mac address. but there are just far too many bytes.
“Remember that everyone you meet is afraid of something, loves something, and has lost something”
• Inactive Imported Users Posts: 167
Now I got your point, meaning 0 ,128 , 256 is my subnet so all below 128 except 127 which is the broadcast address of 0 subnet. is part of ) subnet. 0 subnet and ip range is 1 to 126.

And sorry Mr. Jigsaw it's a typo error.

Thanks and one more question myke are you Filipno?

Chinaman
• Inactive Imported Users Posts: 167
Wait I think D should be included in 128 subnet bec. the next subnet is 256 and 192.4.80.200 is still part of 128 subnet.
• Member Posts: 34 ■■□□□□□□□□
256 will not be a subnet. your subnets here are only 0 and 128. subnet 0 will have host range from 1 to 126 and subnet 128 will have hosts from 129 to 254. broadcasts are 127 for subnet 0 and 255 for subnet 128.

I think youve forgotten that each octet is 8 bits that would make a value of 255 when all bits are on.
“Remember that everyone you meet is afraid of something, loves something, and has lost something”
• Member Posts: 34 ■■□□□□□□□□
chinaman wrote:
Wait I think D should be included in 128 subnet bec. the next subnet is 256 and 192.4.80.200 is still part of 128 subnet.
Yes you are right, D is included but again I wish to point out 256 is not a subnet.
“Remember that everyone you meet is afraid of something, loves something, and has lost something”
• Member Posts: 34 ■■□□□□□□□□
chinaman wrote:
Now I got your point, meaning 0 ,128 , 256 is my subnet so all below 128 except 127 which is the broadcast address of 0 subnet. is part of ) subnet. 0 subnet and ip range is 1 to 126.

And sorry Mr. Jigsaw it's a typo error.

Thanks and one more question myke are you Filipno?

Chinaman

Yes I am Filipino. Good luck on your Exam.
“Remember that everyone you meet is afraid of something, loves something, and has lost something”
• Inactive Imported Users Posts: 167
Pwede ba explain mo sakin ng maige kung bakit hindi kasali ang 256 kasi iniisp ko is 128+128 = 256 +128 again is the next subnet.

thanks
• Inactive Imported Users Posts: 167
You can assign hosts starting from 190.4.80.1 up to 190.4.95.254, from your options, that would be all of them except option f.

Is it 190.4.80.94.254 is the last ip address for the 1st question?
becasue 192.4.80.255 should be my broadcast address the next subnet is 96.
• Inactive Imported Users Posts: 167
Sorry it's not 190.4.80.255 it should be 190.4.95.255 which the next subnet is 96 and before 95 broadcast is 94 which is my last ip address for subnet 80 correct me if I'm wrong Im just practicing my subnetting.

thanks
• Inactive Imported Users Posts: 167
Sorry Myke I think your right that 190.4.95.254 is my last ip address and my last broadcast is 192.4.95.255. I'm totally condufse with subnetting.
• Member Posts: 34 ■■□□□□□□□□
Kabayan! Kamusta. Kaya hindi subnet yung 256 kze diba ang ip address 32 bits lang yun na 8 bits bawat isa. ang maximum ng 8 bits e 255 kaya ang ip address broadcast mo is 255.255.255.255 na lahat one. kaya impossibleng magkaroon ka ng value na 256 sa ip address.

I wish you luck in your exam. Just keep on practicing subnetting and youll get the hang of it. I myself will be taking my ccna next week, and I am pretty much confident I will pass this one.
“Remember that everyone you meet is afraid of something, loves something, and has lost something”
• Inactive Imported Users Posts: 167
Salamat, good luck din sayo. Nga pala one more question this morning I tried to solve this ip address actually I want to subnet 10.0.0.0 /24.

Please help me regarding this subnet actually this example is in the cisco press book pero do deeply understand the example I want to know the list of subnet and ip. I know how to get the number of net and host but I stuck on getting the subnet and ip address since it's a /24 but the ip is class A actually base on the book it is a Private ip but I'm only using this as my private ip in my network so anyway I just want to ask for your help how can I get the list of subnet by using the short method or if not please explain me it to me. Thanks Kabayan and wish you all the best by the way I'm taking intro only although I have some I idea about routing protocols and how to configure it but I'm still having problem with subnetting.

Chinaman
• Inactive Imported Users Posts: 167
Please correct me if I'm wrong regarding my prev. post.

my subnet for this is 10.1.1.0
ip range to 10.1.1.1 to 10.1.1.254

I just subtructed 265 -255 since it will give me 1.
• Member Posts: 83 ■■□□□□□□□□
It is not clear from your post what problem you're trying to solve.
• If the problem is "given the class A network 10.0.0.0, subnet it with mask /24", then the anser is: there are 65536 subnets, 10.0.0.0/24, 10.0.1.0/24, ..., 10.255.255.0/24.
BSEE, MSCS
www.maftei.net
• Member Posts: 53 ■■□□□□□□□□
chinaman wrote:
Please correct me if I'm wrong regarding my prev. post.

my subnet for this is 10.1.1.0
ip range to 10.1.1.1 to 10.1.1.254

I just subtructed 265 -255 since it will give me 1.

Hi, i think I got confused on you query. Anyway, revising your question if I have a class a address (10.0.0.1/24), you would have 254 valid ip adresses with 65536 valid subnets (assuming we are not using CIDR). So you should have:

10.0.0.1 to 10.0.0.254;
Thank you for calling Cisco Technical Assistance Center.. This is Edward how may I help you?
• Inactive Imported Users Posts: 167
Sorry guys, anyway regarding to my question let say i want to subnet 10.20.30.40/24 How can I know my subnet address and broadcast.

10.20.30.40 Class A
255.255.255.0 borrow 16 bits and left 8 bits for host.

correct me if Im wrong my subnet is 10.20.30.0 and again I want to ask you guys why is 20.30 is included. It should be 10.0.0.0 becuase it is a class A address. Can you explain it to me how did it happen

I know my ip range is 10.20.30.1 to 30.38 since my broadcasr is 39

I'm confuse with the 255.255.255.0 then the ip address is a Class A sometimes also in class B when using /29.

Chinaman
• Member Posts: 53 ■■□□□□□□□□
chinaman wrote:
I know my ip range is 10.20.30.1 to 30.38 since my broadcasr is 39

I'm confuse with the 255.255.255.0 then the ip address is a Class A sometimes also in class B when using /29.

I am pretty confused with the question. Are you using CIDR?
Thank you for calling Cisco Technical Assistance Center.. This is Edward how may I help you?
• Member Posts: 53 ■■□□□□□□□□
If you are using plane subnetting this would give you the answers:

10.20.30.1/24

the next network id would be:

10.20.31.0

However if you are going to use CIDR on a class A address with a /29:

i.e

10.20.30.40/29

10.20.30.40 will be your CIDR network
10.20.30.40 to 10.20.30.47 this will be your CIDR network range.
Thus, the next CIDR network will be 10.20.30.48

CIDRs are commonly used for global ip addresses. *routeable ip address to conserve ip addresses but can also be used in rfc1918 (private addresses) for segregation of networks.
Thank you for calling Cisco Technical Assistance Center.. This is Edward how may I help you?
• Inactive Imported Users Posts: 167
ubergeek, Is CIDR included in the ccna intro exam? and regarding to the question I posted, it is incorrect you right if it ask what is the subnet of 10.20.30.1/24 should be 10.20.30.0 and 1st ip is 30.1 to 30.254 and broadcast is 255.

However, want to ask you what is the diff. between CIDR and subnetting?
I know you can save IP address in CIDR or let say you are just allocating a certain IP addresses.
• Inactive Imported Users Posts: 167
Can you teach me CIDR? example 10.20.30.40 /27
Thanks you again
• Inactive Imported Users Posts: 167
10.20.30.40 will be your CIDR network
10.20.30.40 to 10.20.30.47 this will be your CIDR network range.
Thus, the next CIDR network will be 10.20.30.48

256-248 = 8 so subnet is 0 8 16 to 48 ...etc,
so my CIDR is 10.20.30.40 my ip range is .41 to .47
next cidr network is .48

no broadcast address? why? it's like also subnetting but in CIDR your just using the range of ip address. Am I right? but what if I want to add some node but 41 to 47 is already in use? Do I need to re-configure my ip address and borrow more some bits.

thanks
• Member Posts: 53 ■■□□□□□□□□
hmmm.. i'm not sure if it will be included on the ccna intro exam. But it's best to know CIDR in case. Regarding your question for the CIDR, it's a pleasure.

10.20.30.40/27

This ip address will fall to the 10.20.30.32/27 CIDR network:

so the available ip addresses for this network will be:

10.20.30.32 - 10.20.30.63/27

Now how did I get this networks? It is just the same as regular subnetting. Taking into consideration that since you will be using CIDR, you don't need to be confused by the regular notation of the class a subnet which is /8.

Using CIDR for a class a address with a notation of /27: (using shortened method).

you will have 32 maximum hosts and 30 maximum subnets. So I took this from 10.20.30.0/24 to create a CIDR for a /27:

10.20.30.32/27; 10.20.30.64/27; 10.20.30.96 and so on and so forth

so 256-224 = 32 this will be you base for creating CIDR's"
Thank you for calling Cisco Technical Assistance Center.. This is Edward how may I help you?
• Inactive Imported Users Posts: 167
you will have 32 maximum hosts and 30 maximum subnets. So I took this from 10.20.30.0/24 to create a CIDR for a /27:

10.20.30.32/27; 10.20.30.64/27; 10.20.30.96 and so on and so forth

so 256-224 = 32 this will be you base for creating CIDR's"

Okay It's getting clear but I was confuse when you indicate that you took this from 10.20.30.0/24 what do you mean? subnetting 10.20.30.1/24 then you use CIDR. and also why 10.20.30.32 ? it is a subnet.