How to manually calculate an IP range
Hi Expets,
I am a newbie to networking (this is not an exageration!). I have just taken the Network+ course and am now studying to write the certification exam. And to boot, I do not currently work in a networking job (work in IT but not specifically innetworking). So please be patient with me and try to understand if I ask what seems to be a stupid or obvious question.
Here goes...
I have the following scenerio that I am trying to work out in an effort to understand fully how subnetting works....
Address allocation provided by telco is 10.85.0.0 with a 12 bit mask. What is the range of usable ip addreesses?
I have some of the basics figured out (I think). Subnet mask is 255.240.0.0, network id is 10.80.0.0. I used an online subnet calculator to get what the range is but I just cannot figure out how it arrived at the numbers
I believe it has something to do with the second octet of the subnet mask, where, from what I have read and studies, t4 bits were 'stolen' from the hosts. Is this correct? And if so, the next step I think has to do with using all possible on/off combinations for these 4 bits. The prlblem I am running into is that I cannot figure out no way, no how, what on earth I do with this information to come out with the numbers that the calculator gave me!!!
Can some network expert please steer me in the direction I need to go?
Thanks in advance!
Connie
I am a newbie to networking (this is not an exageration!). I have just taken the Network+ course and am now studying to write the certification exam. And to boot, I do not currently work in a networking job (work in IT but not specifically innetworking). So please be patient with me and try to understand if I ask what seems to be a stupid or obvious question.
Here goes...
I have the following scenerio that I am trying to work out in an effort to understand fully how subnetting works....
Address allocation provided by telco is 10.85.0.0 with a 12 bit mask. What is the range of usable ip addreesses?
I have some of the basics figured out (I think). Subnet mask is 255.240.0.0, network id is 10.80.0.0. I used an online subnet calculator to get what the range is but I just cannot figure out how it arrived at the numbers
I believe it has something to do with the second octet of the subnet mask, where, from what I have read and studies, t4 bits were 'stolen' from the hosts. Is this correct? And if so, the next step I think has to do with using all possible on/off combinations for these 4 bits. The prlblem I am running into is that I cannot figure out no way, no how, what on earth I do with this information to come out with the numbers that the calculator gave me!!!
Can some network expert please steer me in the direction I need to go?
Thanks in advance!
Connie
SOLUTION
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i have just had a quick look online for something that explains what I am trying to say better.
http://www.dummies.com/how-to/content/unmasking-the-subnet-mask-for-the-ccna-exam.html
have a read through the link above and i'll clear up any questions you have.
hope this helps
http://www.dummies.com/how-to/content/unmasking-the-subnet-mask-for-the-ccna-exam.html
have a read through the link above and i'll clear up any questions you have.
hope this helps
ASKER
Thanks again Ross for the post.
The funny thing is....I am confortable with the binary math part of all this, including the ANDing and using it to obtain a network id. I even get, to a point, the concept of stealing from the host bits to create more subnets. So why am I not getting how to figure out the ip range here? I think I have all the information needed to do it, just not sure what to do with the inforamtion for some reason
I will think through your first post for abit and see if things clear up for me.
The funny thing is....I am confortable with the binary math part of all this, including the ANDing and using it to obtain a network id. I even get, to a point, the concept of stealing from the host bits to create more subnets. So why am I not getting how to figure out the ip range here? I think I have all the information needed to do it, just not sure what to do with the inforamtion for some reason
I will think through your first post for abit and see if things clear up for me.
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a couple of random snippits of info that might help
11111111 in binary = 255 , thats what gives you 255 as the maximum.
because the subnet mask is 00000000 you can have any combination of zeros and ones up to 255.
--------------------------
for the part of your address
xx.80.x.x
xxx.240.x.x
there is only 15 ip address that will mach the subnet to give you the same network address
11111111 in binary = 255 , thats what gives you 255 as the maximum.
because the subnet mask is 00000000 you can have any combination of zeros and ones up to 255.
--------------------------
for the part of your address
xx.80.x.x
xxx.240.x.x
there is only 15 ip address that will mach the subnet to give you the same network address
good explanation,
disregard my 2nd to last post, eliots explanation is miles clearer.
SOLUTION
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ASKER
OMG Elliot. So all I had to do was flip the 0's to 1\s for the hsot bits?? Will that work all the time? If this is the case I was most definitely making it more difficult than it is in reality. My study books cerrtainly do not explain it like this.
I think I was getting confused in that I was trying to apply the method for creating new networks, which isn't correct. From my book..."Using the original network id you figure out all the possible combinations of on and off states for the bits in the octet you stole them from" If I am now understanding this, I didn't need to do this and was trying to apply this to a scenerio that wasn't relevant?
All the information provided has helped out tremendously and I really appreciate it. But at this point it seems that Elliots explanation has cleared things up and provided the answer I was looking for (I think)
Marshall, your post had really good timing as I was just going over the secion on routing in my book. Had to leave the subnetting part for awhile. The link you provided is very helpful and I will definitely use it as a study aid!!
Thanks all!! I wish I could give everyone who took the time to post 500 points but I know it doesn't work that way. I think I am leaning towards giving the points to Elliot as I believe he made snese of what I was asking and cleared up my dilema.
Connie
I think I was getting confused in that I was trying to apply the method for creating new networks, which isn't correct. From my book..."Using the original network id you figure out all the possible combinations of on and off states for the bits in the octet you stole them from" If I am now understanding this, I didn't need to do this and was trying to apply this to a scenerio that wasn't relevant?
All the information provided has helped out tremendously and I really appreciate it. But at this point it seems that Elliots explanation has cleared things up and provided the answer I was looking for (I think)
Marshall, your post had really good timing as I was just going over the secion on routing in my book. Had to leave the subnetting part for awhile. The link you provided is very helpful and I will definitely use it as a study aid!!
Thanks all!! I wish I could give everyone who took the time to post 500 points but I know it doesn't work that way. I think I am leaning towards giving the points to Elliot as I believe he made snese of what I was asking and cleared up my dilema.
Connie
ASKER
THANKS EXPERTS!!! I really appreciate what you do and that you take the time to help out others.
Connie
Connie
Yes, Connie, it will work every time that setting all host bits to 0 will give you the network address (first address in the range) and then setting them all to 1 will give you the broadcast address (last address in the range). One thing to keep in mind is that those two addresses (network and broadcast) cannot be assigned to a host, so if you are figuring out how many hosts can be used on a given subnet, you need to deduct 2. For example, 10.1.1.0/28 has a range of 10.1.1.0 - 10.1.1.15. This is 16 addresses in all but 10.1.1.0 (network address) and 10.1.1.15 (broadcast address) cannot be used for hosts, so you can only have 14 hosts on that subnet.
Eliot
Eliot
ASKER
At this point your explanation is kind of making sense but I still am not sure on how the lhe last ip address was calculated. According to a subnet calculator, the range is from 10.80.0.0 to 10.95.255.255. I am very confused as to how the 10.95.255.255 was calculated (or any of the in between ones to be honest(.
All the info I have been studying and looking up on the internet is now mubled in my head and I have to make sense of it. I'm sure it will be one specific statement that does it and the light bulb will come one, but unfortunately yours is not it (at least yet)
Connie