IPv6 router advertisement

Ted Lemon Ted.Lemon at nominum.com
Wed May 6 20:00:49 UTC 2009

On May 6, 2009, at 2:34 PM, Mihai Moldovan wrote:
>> Given the symptoms you're describing, my working theory is that
>> Microsoft's autoconf implementation is synthesizing the default route
>> using the source address of the RA message, and Linux is not.
> Sorry for asking such a stupid question, but isn't this was RA is
> actually meant to be used for? Or where does Linux get the router
> address from?

This is what I get for speculating without reading the RFC.   Here's  
what RFC 4861 says:

On receipt of a valid Router Advertisement, a host extracts the source  
address of the packet and does the following:
- If the address is not already present in the host's Default Router  
List, and the advertisement's Router Lifetime is non- zero, create a  
new entry in the list, and initialize its invalidation timer value  
from the advertisement's Router Lifetime field.
- If the address is already present in the host's Default Router List  
as a result of a previously received advertisement, reset its  
invalidation timer to the Router Lifetime value in the newly received  
- If the address is already present in the host's Default Router List  
and the received Router Lifetime value is zero, immediately time-out  
the entry as specified in Section 6.3.5.

So to me this means that the behavior you are seeing is wrong.    
What's the steady-state value of net.ipv6.conf.all.autoconf on your  
linux machine?   Also, do you have any kind of firewall setup on  your  
linux machine?

I'm running 2.6.29 right now, but I've run with earlier versions of  
the kernel on a /64 and not seen this problem.

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