Le 15/04/2010 07:55, Parav Pandit a écrit :
Hi,
As per RFC 2464, Link local address for Ethernet based interfaces
are based on the EUI-64 (derived from the MAC address).
Right, that is probably a very widespread way of how the link local
addresses are derived from a MAC address.
There are many other ways, for example link negotiation with PPP IPv6
which for interfaces not having MAC addresses, like a 3G phone... and
knowing that 3G IPv6 handheld computers (watches, phones, pdas, pads,
netbooks) are potentially very numerous one may think it could be as
widespread as the first.
For these, deriving the MAC address from the link-local address (w/o
doing ND) - will not work.
A case that comes to mind is 6LoWPAN's _some_ version of "6LoWPAN
Neighbor Discovery" which requires the end node to do just that: derive
the MAC address from the LL address. I believe this intention wrongly
aimed.
One shoudl try to identify why would one need to reversely derive the
MAC address from the LL address of some neighbor? Is it to save
messages? We can discuss that and see that sometimes it's not needed to
save, better use point-to-point links.
Why do you need to do this message-less reverse resolution?
I have #3 questions based on this.
In this case, when one Ethernet based host(from its link-local
source) tries to ping the other Ethernet based host, it knows the
Mac address implicitly (from the Link local address).
In this case, if the problem is ping then the solution may be
"ping -I iface" (-I specifies the outgoing interface).
1. Why is it required to explicitly do the Neighbor discovery for
the link-local addresses? RFC 4861 says to do the neighbor discovery
even for link-local addresses. Correct me if my understanding is
incorrect.
IMHO, one aspect is that it requires so in order to have the most up to
date info about the other node. Sometimes nodes change their LLs and
their MAC addresses (ifconfig does that).
2. Does it mean that in Ethernet networks, interface can have only
one Link-local address? If not then we violate the RFC 2464.
I think I can do "ifconfig eth0 add fe80::1/64; ifconfig eth0 add
fe80::2/64; echo $?" and see success, I suppose - have you tried?
3. Does RFC 4941 Privacy extension for autoconf apply to Ethernet
interfaces?
Well yes I believe so, I suppose I have it running on my PC right now.
Alex
Regards, Parav Pandit
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