How do I find the subnet with lack of info..?

Hello all, I have ran across something tonight while taking practice test.

There was a scenario with a network diagram, and I was supposed to figure out what the Subnet prefix of a certain LAN was. Normally this is easy easy for me when I have enough info to work with, but in this question I was lost.

I was given 2 IP addresses:

192.168.10.100 and 192.168.10.122

From that I was supposed to figure out that it was a /26 or 255.255.255.192

________________________________________________________

Maybe I just went blank, but I sure do not have a clue on how they got that answer. I have searched Google on how to figure this out but there is soo much generalized stuff out there about subnetting basics that its hard to find exactly what I am looking for.

- Thanks in advanced. - Shane

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Comments

Forsaken_GA

Any chance you can post the diagram?

sthompson86

Well I did start to, but its from the Boson Practice exams, and I know how some people on here are really ticky when it comes to showing copyrighted stuff.

Basically what the diagram was was a Router with a LAN connected to it. 192.168.10.100 was the router interface and 192.168.10.122 was the IP address of the host.

I am used to seeing more info like /24 /26 or 255.255.255.192 etc, which give me some working room to figure out what subnet the IP address range is on.

But this question only had 2 IP addresses with no subnet info, and the question was wanting to know what Prefix the 2 IP addresses belonged 2 - I am lost lol

Thanks

Forsaken_GA

Well, it's kind of hard to tell without the full context hehe. It's possible it was a bad question, it's also possible that the diagram or the text of the question had a hint.

docrice

I had a question like this in an interview for a desktop support position back in 2000. It was basically, "Given two addresses, determine the most restrictive subnet mask." I had no clue how to perform that back then.

If that's what the question is implying, then I can see where they're coming from.

impz

sthompson86 wrote: »

Hello all, I have ran across something tonight while taking practice test.

There was a scenario with a network diagram, and I was supposed to figure out what the Subnet prefix of a certain LAN was. Normally this is easy easy for me when I have enough info to work with, but in this question I was lost.

I was given 2 IP addresses:

192.168.10.100 and 192.168.10.122

From that I was supposed to figure out that it was a /26 or 255.255.255.192

________________________________________________________

Maybe I just went blank, but I sure do not have a clue on how they got that answer. I have searched Google on how to figure this out but there is soo much generalized stuff out there about subnetting basics that its hard to find exactly what I am looking for.

- Thanks in advanced. - Shane

From what I understand from the info provided, I think that you need to find a subnet mask where the the 2 IP addresses would be valid hosts in.

/24 /25 /26 /27 would be correct and I'm assuming the /24 /25 /27 wasnt in the possible choices ? ...... or there is a bit more info to eliminate /24 /25 and /27?

mella060

The only possible subnet masks that you could use would be /24 /25, /26 or /27. But you can probably rule out a /24 or /25 mask since the question most likely wants a more specific mask to be used. A /27 mask, which is the most specific mask that includes the two addresses is probably the answer that they are after.

A /26 would include 62 possible host addresses

192.168.10.64 would be the subnet address

The host range would be 192.168.10.65 - 126

A /27 would include 30 possible host addresses

192.168.10.96 would be the subnet address

The host range would be 192.168.10.97 - 126

sthompson86

docrice wrote: »

I had a question like this in an interview for a desktop support position back in 2000. It was basically, "Given two addresses, determine the most restrictive subnet mask." I had no clue how to perform that back then.

If that's what the question is implying, then I can see where they're coming from.

Thats exactly what it was asking lol

sthompson86

mella060 wrote: »

The only possible subnet masks that you could use would be /24 /25, /26 or /27. But you can probably rule out a /24 or /25 mask since the question most likely wants a more specific mask to be used. A /27 mask, which is the most specific mask that includes the two addresses is probably the answer that they are after.

A /26 would include 62 possible host addresses

192.168.10.64 would be the subnet address

The host range would be 192.168.10.65 - 126

A /27 would include 30 possible host addresses

192.168.10.96 would be the subnet address

The host range would be 192.168.10.97 - 126

Thank you sir.