working out subnet mask from IP

[cisco8887]

hi guys,

is it possible to derive a subnet mask of an ip from its IP ?

I am sure the answer is no but wanted to ask.

for instance I give you an ip address of 100.0.0.1  and you are ping it from 200.0.0.1 with no access to the router that is providin/forwarding traffic for 100.0.0.1 .

You can't work out the subnet, right?

Thanks

[Karsten Iwen · Accepted solution]

If you travel back in time, there could be a way to find this out. Today, that shouldn't work any more.

[cisco8887]

many thanks, if disabled option then i won't bother

Thanks for letting me know

I didn't know such icmp existed

[Karsten Iwen]

> I didn't know such icmp existed

And in the future, you'll never need to know that again ... ;-)

[cisco8887]

:) you are very knowledgable . how many years of experience do you have if you don't mind me asking .

[Karsten Iwen]

The new year started really good and now I suddenly feel really old ;-)

About 20 years, 15 with Cisco-stuff ...

[cisco8887]

impressive :)

on my route to CCIE