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

Thu Aug 21 08:09:58 UTC 2008

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...