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IPv6 implementation...

To: netdev@xxxxxxxxxxx
Subject: IPv6 implementation...
From: Fabrizio Morbini <fabrizio.morbini@xxxxxxxxxx>
Date: Fri, 22 Feb 2002 09:11:07 +0100
Sender: owner-netdev@xxxxxxxxxxx
Hi at all, I'm  testing IPv6 (and I'm not an expert) I have encountered
a problem and after an exchange of some
mail with the autor of the IPv6 HowTo (Peter Bieringer) I have decided
to ask you:

#situation
-gateway
kernel 2.4.8 of Mandrake 8.1;
IPv6 in IPv4 tunnel with freenet6.net and /48 network;
-clients
kernel 2.4.17 from www.kernel.org;
one of the /48 address;

#problem
-on the gateway all runs fine for example:
ping6 ftp6.edisontel.com
-on the clients
ping6 ftp6.edisontel.com receive from the gateway the response:
Destination unreachable: Address unreachable.

IPv6 forwarding is enabled.
The problem was resolved adding the line route -Ainet6 add 2000::/3 dev
sit1 to the gateway routing table.

The strange behaviour is:
[IPv6 icmp6 packet] ->from the client to the gateway-> the gateway open
the packet see the destination address: 2001:750:2:0:202:a5ff:fefb:49ec
see it's routing table and then respond to the client:
>From 3ffe:b80:8a9:1::1: Destination unreachable: Address unreachable
(3ffe:b80:8a9:1::1 is the gateway)
But if the packet is generated by the gateway (change only the source
address): the kernel add the necessary routing line into the
routing table and all runs fine. Why the kernel doesn't add this line
also when the source address of the packet isn't one of it's
network interfaces?

(the line added is: 2001:750:2:0:202:a5ff:fefb:49ec/128        
2001:750:2:0:202:a5ff:fefb:49ec         UC    0      2        1 sit1   )

The question is:
Tcpdump doesn't report useful information (it's sniffing is:
09:05:08.711200 3ffe:b80:8a9:1:250:baff:fe0e:4d52 >
2001:750:2:0:202:a5ff:fefb:49ec: icmp6: echo request
09:05:08.711311 3ffe:b80:8a9:1::1 > 3ffe:b80:8a9:1:250:baff:fe0e:4d52:
[|icmp6])
How I can view why the packet from the clients doesn't follow the same
behaviour of the packet created directly
on the gateway?

Thank you very much for any help and Best Regards.
Fabrizio

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