Grant Taylor a écrit :
Pascal Hambourg wrote:
Iptables will happily redirect anything you like to localhost, but the
kernel IP routing prohibits communications with a loopback address on
a non loopback interface and thus will drop the packets.
Does this apply if the reverse path filter is turned off?
Yes. This is not a reverse path issue, as rp_filter=1 checks only the
source address, not the destination address.
Or is this a
hard coded filter in the kernel that can not be gotten around?
AFAIK, it is hard coded. I guess the reason is that RFC 3330 reserves
127.0.0./8 for the loopback and prohibits its use on any network outside
the host. Unfortunately, the routing code does not know that the packet
was DNATed and has an original non-loopback destination address.
Another thought to the OP would be to use the Dummy interface in lieu of
the Loop Back interface as I believe it does not have the same
restrictions that Loop Back does. However I could be mistaken.
I do not see how a dummy interface might be useful here. Can you please
clarify ?
I have often considered using lo for local only but using dummy as a
spur network to bind services to and then route traffic in to the spur
network. Thoughts / Opinions?
A dummy interface is a black hole, a kind of "/dev/null" interface,
traffic you route to it is lost. This is very different from a loopback
interface, whose traffic you route to it loops back and is received by
the local host. It is fine to use a dummy interface if you want to add
an extra address to the host and bind services to it, but I guess you
could do the same with the loopback interface.
