v6 subnet size for DSL & leased line customers

Tony Li tony.li at tony.li
Wed Dec 26 18:22:07 UTC 2007


On Dec 26, 2007, at 8:26 AM, Leo Bicknell wrote:

> In a message written on Tue, Dec 25, 2007 at 12:43:45AM -0500,  
> Kevin Loch wrote:
>> RA is a shotgun.  All hosts on a segment get the same gateway.  I  
>> have
>> no idea what a host on multiple segments with different gateways  
>> would
>> do.  Hosting environments can get complex thanks to customer
>
> I would like to point out that in IPv4 we have ICMP Router
> Advertisement messages.  I have never seen them used on a production
> network.  I know one of the worries is security, that a compromised  
> host
> could send out advertisements, drawing traffic to it that it can then
> snoop and pass on to the real gateway.
>
> Having not looked in great detail, I am unclear if IPv6 has done
> something to fix this concern or not.
>
> Is this feature going to get turned off when the first worm comes  
> along
> that spoofs RA's
>


It's unlikely that it will matter.  In practice, ICMP router  
discovery died a long time ago, thanks to neglect.  Host vendors  
didn't adopt it, and it languished.  The problem eventually got  
solved with HSRP and its clone, VRRP.

This doesn't resolve the real underlying problem: Ethernet is  
inherently insecure.  MAC addresses can be forged, protocols (ARP,  
ND) can be forged and at this point, there's not much that we can do  
about it.  Architecturally, we need authentication over each and  
every control plane packet sent.  Getting there without invoking the  
full complexity of a public key infrastructure is still an unsolved  
problem, AFAIK.

Tony




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