[c-nsp] IPv6 subnets for point-to-point links

[Crist Clark]

Yucel Guven wrote:
> Crist,
> Routers need to identify networks uniquely, e.g, if a router has 50 x p2p
> subinterfaces, it must know into which subif the packet has to be forwarded.
> For this purpose, netmasks are inevitable.

No, they aren't.

> IPv6 doesn't need any broadcast mechanism, but we still need to identify 
> our subnets, uniquely.

There is no subnet. This is a point-to-point link!

The whole point of a netmask is when you have an interface connected to
a broadcast network with (potentially) many hosts, a host figures out
whether another one is local by checking the remote host's address
against the netmask. If you have a point-to-point link, there's only
one host, and it's local. Who needs a netmask?

In either IPv4 or IPv6 a P-to-P link does not need a subnet. There is no
reason, and this actually happens all of the time, I can't have a P-to-P
link like,

	10.10.10.100 <---> 172.20.20.10

And have a perfectly happy router and network. (This is especially true
for leaf nodes, but you can do it in the middle of your network too.)

Similarly, if we need to worry about netmasks of P-to-P links, why does
IPCP, the Network Configuration Protocol for IP over PPP, have no
mechanism at all to communicate a network mask between the peers?

> Btw, I also used /126 for p2p links on GSR12000 (with T-series image) without any problem
> -Yucel
> "..and outside the bright lights, can't hide the pain inside..." S.O.C. 
> -----------------------------------------------------------
> 
> 
>>In the IP world, or any world for that matter, why does one need to
>>assign a netmask to a point-to-point link at all? A point-to-point
>>link is, by definition... uh, point-to-point. Netmasks are for broadcast
>>media.
>>
>>The need for netmasks on a point-to-point link only happens when you
>>pretend a broadcast link is point-to-point.
>>
>>Please enlighten me if I'm missing something here.
>>--
>>Crist J. Clark                               crist.clark at globalstar.com
>>Globalstar Communications                                (408) 933-4387
> 
> 


-- 
Crist J. Clark                               crist.clark at globalstar.com
Globalstar Communications                                (408) 933-4387

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