# Network 10.1.0.0/16 with broadcast address 10.2.1.1?

## dE_logics

If a network 10.1.0.0/16, or let's say the IP 10.1.0.1/16 has a broadcast address of 10.2.1.1, will it be ridiculous?

But this's exactly what the ip command allows. You can set any broadcast address we want. I don't understand the point of 10.2.1.1 as a broadcast address. How is this supposed to work?

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## eccerr0r

Yeah I think that's wrong, not sure what it will do, if anything at all.  I thought the smallest possible subnet that could be useful was a /30.

Only reference I found to a /31 is http://tools.ietf.org/html/rfc3021 and is fairly recent due to ip address conservation - which is implied by a broadcast with 10.2.1.1.

I also wonder about the ambiguity of a broadcast address, of say, 11.13.255.255

Is this 11.8.0.0/18 or 11.13.0.0/16?

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## dE_logics

 *eccerr0r wrote:*   

> Yeah I think that's wrong, not sure what it will do, if anything at all.  I thought the smallest possible subnet that could be useful was a /30.
> 
> Only reference I found to a /31 is http://tools.ietf.org/html/rfc3021 and is fairly recent due to ip address conservation - which is implied by a broadcast with 10.2.1.1.
> 
> I also wonder about the ambiguity of a broadcast address, of say, 11.13.255.255
> ...

 

For network 11.8.0.0/18 it must be 11.8.255.255; I'm not sure if 11.8.0.0/18 is a valid network ID. It should be at least 11.8.1.0/18. The broadcast of this network will be 11.8.127.255

11.13.0.0/16 will have a broadcast 11.13.255.255

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## eccerr0r

Whoops... Typoed.  Not 11.8.0.0/18, but 11.8.0.0/14 ... Now is this a valid network, and is its broadcast 10.13.255.255.  Then again 10.13.0.0 /16 is completely within 10.8.0.0/14

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## papahuhn

11.8.0.0/18 is valid as well. Its hosts are 11.8.0.1 - 11.8.63.254 with broadcast 11.8.63.255. Also, 11.8.1.0/18 is not a network, it is a host within 11.8.0.0/18.

 *Quote:*   

> Then again 10.13.0.0 /16 is completely within 10.8.0.0/14

 

10.8.0.0/14 has hosts from 10.8.0.1 to 10.11.255.254, so 10.13.0.0/16 is disjoint with it.

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## eccerr0r

Argh... 1011 in binary is not 13... grr.. Yes that was supposed to be 11.

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