Subnetting

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#2
For subnetting scenarios that I give to my students, I specify the size of the subnetworks as well (either varied with specifics or equal size).
In that way, I would have a specific answer that I can use to check if my students have done them correctly or not.

If you just say make 11 networks, then they can have varied responses which could strain you with marking/checking
 
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#3
nateg said:
How does one prove if his subnetting is correct?

for example on 172.16.0.0 and I'm making 11 networks

How do I prove that what I'm doing is correct? I hope I'm making sense :)
Click to expand...
To be blunt: your question mentions zero information about subnet masks, desired network size, etc. So your question is incomplete. There is nothing to prove.
 
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#4
Tess Sluijter said:
To be blunt: your question mentions zero information about subnet masks, desired network size, etc. So your question is incomplete. There is nothing to prove.
Click to expand...
Quite right. Without a subnet mask, the general assumption is that we're talking about a Class B address, which suggests the mask is going to be 255.255.0.0. Of course, that's assumptive in the absence of the mask or CIDR notation.

However, to complete the square, let me suggest that a mask of 255.255.240.0, or a /20 applied to 172.16.0.0 will create 11 networks. (actually it creates 16).
172.16.0.0 - 172.16.0.15
172.16.0.16 - 172.16.0.31
172.16.0.32 - 172.16.0.47
172.16.0.48 - 172.16.0.63
172.16.0.64 - 172.16.0.79
172.16.0.80 - 172.16.0.95
172.16.0.96 - 172.16.0.111
172.16.0.112 - 172.16.0.127
172.16.0.128 - 172.16.0.143
172.16.0.144 - 172.16.0.159
172.16.0.160 - 172.16.0.175
172.16.0.176 - 172.16.0.191
172.16.0.192 - 172.16.0.207
172.16.0.208 - 172.16.0.223
172.16.0.224 - 172.16.0.239
172.16.0.240 - 172.16.0.255

Additionally, remember that when CompTIA asks about what the mask needs to be to get "this many networks/hosts", they are looking for the bare minimum. Naturally, /21 /22, etc will also give you 11 networks, but in questions like this, they are looking for the line. So a /20 will give you the 11 networks you need, but a /19 will not (that only produces 8).

/r
 
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#5
Agree with the above. Sharing on related note, this is a good practice site or can be used to generate scenarios.

IPv4 Subnetting Practice

Practice IPv4 Subnetting with a problem generator. Still learning? Great! We have the BEST Subnetting instructional videos on the planet -- all free!
subnetipv4.com

Lee
 
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#7
A nice way to illustrate subnetting is defining a particular need, like a router to router network, where all you want to end up with is two valid host IP addresses for the subnetwork (255.255.255.252). Example:

172.16.0.0 = Network Address
172.16.0.1 = Host 1
172.16.0.2 = Host 2
172.16.0.3 = Broadcast Address
 
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#10
Rick Butler said:
Quite right. Without a subnet mask, the general assumption is that we're talking about a Class B address, which suggests the mask is going to be 255.255.0.0. Of course, that's assumptive in the absence of the mask or CIDR notation.

However, to complete the square, let me suggest that a mask of 255.255.240.0, or a /20 applied to 172.16.0.0 will create 11 networks. (actually it creates 16).
172.16.0.0 - 172.16.0.15
172.16.0.16 - 172.16.0.31
172.16.0.32 - 172.16.0.47
172.16.0.48 - 172.16.0.63
172.16.0.64 - 172.16.0.79
172.16.0.80 - 172.16.0.95
172.16.0.96 - 172.16.0.111
172.16.0.112 - 172.16.0.127
172.16.0.128 - 172.16.0.143
172.16.0.144 - 172.16.0.159
172.16.0.160 - 172.16.0.175
172.16.0.176 - 172.16.0.191
172.16.0.192 - 172.16.0.207
172.16.0.208 - 172.16.0.223
172.16.0.224 - 172.16.0.239
172.16.0.240 - 172.16.0.255

Additionally, remember that when CompTIA asks about what the mask needs to be to get "this many networks/hosts", they are looking for the bare minimum. Naturally, /21 /22, etc will also give you 11 networks, but in questions like this, they are looking for the line. So a /20 will give you the 11 networks you need, but a /19 will not (that only produces 8).

/r
Click to expand...
Thank you for this.
 
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#11
Lee McWhorter said:
Agree with the above. Sharing on related note, this is a good practice site or can be used to generate scenarios.

IPv4 Subnetting Practice

Practice IPv4 Subnetting with a problem generator. Still learning? Great! We have the BEST Subnetting instructional videos on the planet -- all free!
subnetipv4.com

Lee
Click to expand...
Thank you.
 
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#12
Rick Butler said:
Quite right. Without a subnet mask, the general assumption is that we're talking about a Class B address, which suggests the mask is going to be 255.255.0.0. Of course, that's assumptive in the absence of the mask or CIDR notation.

However, to complete the square, let me suggest that a mask of 255.255.240.0, or a /20 applied to 172.16.0.0 will create 11 networks. (actually it creates 16).
172.16.0.0 - 172.16.0.15
172.16.0.16 - 172.16.0.31
172.16.0.32 - 172.16.0.47
172.16.0.48 - 172.16.0.63
172.16.0.64 - 172.16.0.79
172.16.0.80 - 172.16.0.95
172.16.0.96 - 172.16.0.111
172.16.0.112 - 172.16.0.127
172.16.0.128 - 172.16.0.143
172.16.0.144 - 172.16.0.159
172.16.0.160 - 172.16.0.175
172.16.0.176 - 172.16.0.191
172.16.0.192 - 172.16.0.207
172.16.0.208 - 172.16.0.223
172.16.0.224 - 172.16.0.239
172.16.0.240 - 172.16.0.255

Additionally, remember that when CompTIA asks about what the mask needs to be to get "this many networks/hosts", they are looking for the bare minimum. Naturally, /21 /22, etc will also give you 11 networks, but in questions like this, they are looking for the line. So a /20 will give you the 11 networks you need, but a /19 will not (that only produces 8).

/r
Click to expand...
With a /20 I assume the networks have to be
172.16.0.0 - 172.16.15.255
172.16.16.0 - 172.16.31.255
172.16.32.0 - 172.16.47.255
172.16.48.0 - 172.16.63.255
172.16.64.0 - 172.16.79.255
172.16.80.0 - 172.16.95.255
172.16.96.0 - 172.16.111.255
172.16.112.0 - 172.16.127.255
172.16.128.0 - 172.16.143.255
172.16.144.0 - 172.16.159.255
172.16.160.0 - 172.16.175.255
172.16.176.0 - 172.16.191.255
172.16.192.0 - 172.16.207.255
172.16.208.0 - 172.16.223.255
172.16.224.0 - 172.16.239.255
172.16.240.0 - 172.16.2545.255
 
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#13
Ramasankar said:
With a /20 I assume the networks have to be
172.16.0.0 - 172.16.15.255
172.16.16.0 - 172.16.31.255
172.16.32.0 - 172.16.47.255
172.16.48.0 - 172.16.63.255
172.16.64.0 - 172.16.79.255
172.16.80.0 - 172.16.95.255
172.16.96.0 - 172.16.111.255
172.16.112.0 - 172.16.127.255
172.16.128.0 - 172.16.143.255
172.16.144.0 - 172.16.159.255
172.16.160.0 - 172.16.175.255
172.16.176.0 - 172.16.191.255
172.16.192.0 - 172.16.207.255
172.16.208.0 - 172.16.223.255
172.16.224.0 - 172.16.239.255
172.16.240.0 - 172.16.255.255
Click to expand...
You would be right. I actually ran a /28 not a /20. It was an early morning without coffee. Nice work. /r
 
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