It's Ars Tech's turn to bang the IPv4 exhaustion drum

Sun Aug 24 01:41:16 UTC 2008

On 21 Aug 2008, at 09:09, Iljitsch van Beijnum wrote:

> On 20 aug 2008, at 21:33, Crist Clark wrote:
>
>> No, that's my point. On a true point-to-point link, there is
>> only one other address on the link. That's what point-to-point
>> means.
>
>> For example, on the IPv4 ends gif(4) tunnel in my previous message,
>
>>
>> gif0: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> metric 0 mtu 1280
>>        tunnel inet 24.6.175.101 --> 72.52.104.74
>>        inet6 fe80::200:24ff:feca:91b4%gif0 prefixlen 64 scopeid 0x7
>>        inet6 2001:470:1f04:2fc::2 --> 2001:470:1f04:2fc::1  
>> prefixlen 128
>
> Note that this interface doesn't _have_ any IPv4 addresses: the  
> IPv4 addresses that you see are the tunnel endpoints.
>
> However, the IPv6 addresses do what you say: there is a local one  
> and a remote one and they don't share a subnet. Obviously it's  
> possible to do this, but in my opinion, this is just an  
> implementation variation, not the natural state of point-to-point  
> links. It makes much more sense to have one set of behaviors that  
> applies to all interfaces.
>
> And what is a point-to-point link, anyway? In theory gigabit  
> ethernet is CSMA/CD, but I don't think anyone ever bothered to  
> implement that, in practice it's point-to-point on layer 1, but  
> layer 2 is point-to-multipoint...
>
>

1000BASE-PX10 and 1000BASE-PX20 are both point to multipoint at layer 1.