Hi,

I have read several times on this group that on linux systems by default
IPv4 packets received by  a host will be answered irrespective of which
interface the packets are received on. For instance, if you have a
multihomed linux host and you configure one IPv4 address, A, on say eth0
and another IPv4 address, B, on say eth1, then pings for B that are
received on eth0 will be answered by the linux host.

Is the same true for IPv6 addresses?

What I see on my Redhat FC4 PC (kernel version 2.6.11 according to
/proc/version), is if I assign say 192.168.78.101/24 to eth0 and
192.168.78.105/24 to dummy0 and then ping 192.168.78.105 from another
host connected to eth0, the PC answers the pings.

But if I do the analogous thing with IPv6 addresses (in this case I
assigned 2001::2/64 to eth0 and 2001::4/64 to dummy0) and try to ping6
from the connected host, the PC answers pings to 2001::2 but not those
to 2001::4. Running ip neigh show on the other host (also a linux 2.6
system but not a PC) says:

2001::4 dev eth0  nud failed

Running ethereal on the Redhat PC shows that the PC is receiving ICMPv6
Neighbor solicitation packets from the other host containing ICMP type
135 target 2001::4, but shows no responses to these solicitations being
transmitted.

Is this the expected behavior?

Is there some twiddling down in /proc that will make it respond to IPv6
addresses irrespective of received interface as with IPv4 addresses, or
are the protocol specs just different in this regard?

Thanks,

Jeff Haran
Brocade
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