[f-nsp] Problem with IPv6 anycast

[Wido den Hollander]

Hi Philipp,

Attached is my pcap from Wireshark.

My subnet is: 2a00:f10:10a:5::/64

RX-8 #1: 2a00:f10:010a:5::1
RX-8 #2: 2a00:f10:010a:5::2
Anycast: 2a00:f10:010a:5::3

My client: 2a00:f10:010a:5:0:1337:6:79

If you check the pcap file, it seems that the RX is responding
incorrect, isn't it?

As you can see, the ::3 address is working fine on the internet (You can
ping it), but not in the local network.

Is this a bug in RX-8?

Regards,

Wido

On Tue, 2010-11-30 at 18:24 +0100, Philipp Geschke wrote:
> Hello,
> 
> On Tue, 30 Nov 2010 15:36:20 +0100, Wido den Hollander <wido at widodh.nl>
> wrote:
> > When analyzing the traffic with Wireshark I see that the RX-8 responds
> > to the ND with it's unicast address, the ::2 in this case.
> 
> Depending on what you mean this is a wrong behaviour.
> The router MUST respond with it's UNIcast address as source address (as
> anycast addresses must not be the source address of an IPv6 packet, see
> RFC
> 3513 section 2.6) but the Target field of the ICMP message MUST be the
> Target field of the Neighbor solicitation that prompted the advertisement
> (See RFC2461 Section 4.4). If you specified the anycast address as the
> gateway this should be the anycast address.
> 
> So a correct Neighbor Solicitation for an IPv6 anycast address with a
> Linux client that has ::10 would basically look like this:
> 
> Client: Source ::10, Target field ::3
> Router: Source ::2, Target field ::3
> 
> This would work with Linux, at least tested with Debian.
> 
> What NI MLX does is:
> 
> Client: Source ::10, Target field ::3
> Router: Source ::2, Target field ::2
> 
> This will not work and is a bug. I have opened a bug report with Brocade
> and it's a confirmed defect.
> 
> If you want, send me a pcap or tcpdump output of your Neighbor
> Solicitation and I will tell you what the RX does wrong.
> 
> > Strange thing is, a Windows 2k3 machine works fine with the anycast
> > address as it's default gateway.
> 
> I have no working knowledge of IPv6 behaviour of Windows, so I really
> can't tell you why it is working. :(
> 
> 
> Regards,
> Philipp
> 
> 
> 
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