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Hi there, I'm a newbie in networking, could anyone tell me what's the following question talking about? Supernetting, right????
What will be the result after changing that?
more hosts, right????
Your help is highly appreciated~~~Thanks a million!"An organization is about to change their network from a shared environment using hubs and one router, to that of a switched environment. A consultant has suggested that the subnet mask on all machines needs to change from 255.255.255.0 to 255.255.248.0."
Explain "why" this should be the case and what the "resulting effect" will be.
There are many reason's, what IP range are you working with ? 10.X.X.X subnet. Here is why, 255.255.255.0 is a default mask for a Class C address, stating that 255.255.255 is the network portition and 0 is the host range. You might be moving to a Class A or class B address range giving you more subnets to work with and more host on each subnet.. with 255.255.255.0 == you get only get 254 - 2 host's (2^8 power)with 255.255.248.0 you get 2048 - 2 hosts per subnet(2^11 power), room to grow..
here is a website about subnetting and you should down load a IP calculator, there are free one's.. Cisco has one and wildpackets also has a free one.
www.learntosubnet.com
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One other note:
Just Remember you Can't have more than 1024 hosts per Broadcast domain or network segment or you will run into problems, Then he should only use (2^10)==1024 -2 = 1022 hosts, 2048 hosts per subnet is an over kill. I would only use 255.255.252.0 (1024) not 255.255.248.0 (2048)..
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The previous responses are addressing a subnetting scenario, not a supernetting scenario. There is a difference. You subnet to increase the number of networks. So if you use a 10.x.x.x IP range, with the standard mask of 255.0.0.0, you would have one network with 16million+ host - not practical. So usually, the default mask is not used. Instead, the IP range in broken into smaller networks. A mask of 255.255.0.0 may be used instead. This give more networks available, and therefore fewer hosts. A determination is made as to what the appropriate mask would be. We could write a book on the possiblilities. Your question referneced supernetting. This is the opposite of subnetting. You don't give enough info as to whether or not you are actually wanting to do supernetting or not. Supernetting's main objective usually to combine multiple networks to appear as one network - usually to reduce the size of routing tables.
A bit more specific info is needed to correctly answer your question. What is your current network setup- your current IP range and mask(s) and why the need for a change?
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Ok, I'll reply to my own post. I see you did say your current mask is 255.255.255.0 and the consultant wants to change it to 255.255.248.0. Without knowing the IP range, you still can't say if it's supernetting or subnetting. If you are combining serveral class C adresses, for example 192.168.1.x, 192.168.2.x, etc, then this would be supernetting. If your current IP range is a class A address that initially was configured with a class C mask and you need more hosts than the class c mask offers, then he is probably suggesting the new mask to increase the number of hosts.
Again, we still need a bit more info.
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I was just giving her and idea why he wants to change the mask... everyone will look at this question a bit diff.. I agree, we need more info..
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Hello all. I am trying to make two subnets
talk to each other i have the following:
linux realworld (eth0) and 192.#.2.1 (eth1)
nt4.0 network (1nic) and 192.#.2.2The 192.2 subnet is a direct connect via a
crossover cable. The nt is a PDC and I want
my other users to be able to access the Linux
box via samba via the 192.2 netowrk. I
have route added till I'm blue in the face
with no luck anyone know what I need to do?
I have done this on another subnet using linux
with no problems but can get NT to do the same.If I'm not clear enough just send me a line
above or post here. As well with the how to.Thank you for you time.
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You need to setup a layer 3 device (router) in-between the two subnet's. what is the full subnet? or turn on IP Forwarding which is the same as setting up a router.
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Hi Brian , Glen and Jimmy
Thanks for your prompt replies!
The question is just that, he didn't give me more information.
In fact I'm not sure it's subnetting or supernetting, so seeking help from you guys.
What do you guys think if that's all the information provided.
You guys are really nice, thanks you so much~~~~~
Question:
"An organization is about to change their network from a shared environment using hubs and one router, to that of a switched environment. A consultant has suggested that the subnet mask on all machines needs to change from 255.255.255.0 to 255.255.248.0."
Explain why this should be the case and what the resulting effect will be.
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To increase more hosts on each subnet for further growth , going from 254 hosts to 2046 hosts per subnet. This is not supernetting.
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Brian, I agree it is probably not supernetting and he is probablly changing the mask to increase the number of hosts. The key word is 'probably'. There is no way you can say this with certainty. If you change the mask of several class C address from 255.255.255.0 to 255.255.255.248, this is supernetting. If you change the mask of a class A address from 255.255.255.0 to 255.255.248.0, this is still subnetting. The point is, without knowing the IP address range there is no way you can answer the question with certainty.
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Supernetting is a kind of Cisco term, example..
let say you have 5 router in one area and we must be using IP Classess to do Supernetting, your really doing VLSM..
and say
router 1 10.1.1.0 255.255.255.0
router 2 10.1.2.0 255.255.255.0
router 3 10.1.3.0 255.255.255.0
router 4 10.1.4.0 255.255.255.0
router 5 10.1.5.0 255.255.255.0and your running say OSPF, now what you can do is, setup supernetting, and just pass 10.1.X.X (255.255.255.0) to the next area, because 10.1 is common to all 5 subnets, they HAVE to be contiguous Subnets before you can do supernetting in that area..
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Agreed, sort of - except the 255.255.255.0 mask would be incorrect for the supernetted mask. That mask would still indicate 5 different subnets.
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I don't know the answer but I suspect this is some kind of a class Nicole is taking...but re-reading the question the issue seems to be the CHANGE from a hub and router to a switch...
If so, could changing the mask allow for more nodes to accomodate VPN's for example...or could it be intreperted as essentially integrating 2 or more networks into the same collision domain that the router now separates???...the changing of the mask would be to increase the number of nodes to allow for the other network...
Again, I don't know, just some thoughts...
Steve
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I tend to agree with Steve that Nicole is
taking a class and this is a case study.First, subnetting is the act of splitting a
natural (classful) into smaller subnetworks.Supernetting is act of aggregating
(combining) 2 or more networks (CIDR).Now, you subnet when you do not have a lot
of hosts, but for admin reasons (more than
1 location for example) you want multiple
networks so you can route.You aggregate for 1 of two reasons. Either
you have a large network and want to
simplify your core routing, or the answer
you are looking for, you need more hosts
in a network so that it can be flat
(switched) and you don't need a router.I tend to agree with Brian, more than 1024
devices on a network can be trouble.-J
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It's not Classful, Classful you can't pass the mask, classless you can..
OPSP
EIGRP
ISISThese are Classless, you have to be running a classless routing protocol to do supernetting
http://safari.oreilly.com/main.asp?bookname=iprouting&snode=52
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