/31 on 2 interfaces

[Kim Shrier]

A /31 is not a point-to-point link.  A /32 is.  A /31 is a network  
with nothing
but a loopback and broadcast address.  You have to go to a /30 to  
have a block
of addresses that is useful or configure a point-to-point link where  
you specify
the address at each end of the link.

Kim

On May 16, 2006, at 7:09 PM, Baldur Gislason wrote:

> /31 is common practice today. You don't need broadcast on a point- 
> to-point link.
> The only broadcast you need is ARP and that's on layer 2.
>
> Baldur
>
> On Tue, May 16, 2006 at 05:55:46PM -0700, John-Mark Gurney wrote:
>> Unix-Solutions - Steven wrote this message on Wed, May 17, 2006 at  
>> 02:10 +0200:
>>> I have 2 servers with both 2x 'em' interfaces in it.
>>> I configged a /31 on both interfaces
>>> em0 in box 1 = 10.0.0.1
>>> em0 in box 2 = 10.0.0.2
>>
>> As someone else mentioned even if you did a /31, those addresses  
>> aren't
>> on the same network...
>> 254 & 1 == 0
>> 254 & 2 == 2
>>
>> Hence different networks.. the other thing is that you can't have  
>> a /31
>> due to the fact that one ip w/ all the node bits set is the broadcast
>> for the network causing other sorts of troubles...  the smallest  
>> usable
>> network is a /30...
>>
>> -- 
>>   John-Mark Gurney				Voice: +1 415 225 5579
>>
>>      "All that I will do, has been done, All that I have, has not."
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--
  Kim Shrier - principal, Shrier and Deihl - mailto:kim at tinker.com
Remote Unix Network Admin, Security, Internet Software Development
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