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Description of problem:

RHEL 3 machine is routing/forwarding to internal interfaces regardless
of /proc/sys/net/ipv4/ip_forward value.





Version-Release number of selected component (if applicable):
kernel-2.4.9-e.38

How reproducible:
Always

Steps to Reproduce:

   scenario and equipment used:
an RHL 7.3 box which is multi-homed, 
and an RHEL AS 3 system which is also multi-homed.
neither of the machines are configured as routers.

configuration basis of test:
when using a client homed in one of the RHL 7.3/RHEL AS 3 LANS and
using the
relative local interface on the RHL 7.3/RHEL AS 3 server as the
clients default
gateway:




Actual Results:  pinging the opposing network interface of the
multi-homed RHEL AS 3 machine shows that:
the client can ping the opposing network interface regardless of
ip_forward being active or inactive.
Thus the machine is routing/forwarding across the internal bus to
internal interfaces and ignoring the ip_forward disable. 

Expected Results:  Expected results of a simple ping from a client to
the opposing interface on the multi-homed machine using the RHL 7.3
machine as an example:
when ip_forward is turned on it is possible to ping the other interface of
the multi-homed RHL 7.3 machine

When ip_forward is turned off it is not possible to ping the other
interface of the
multi-homed RHL 7.3 machine.

Just to re-iterate:
However this same scenario applied to the RHEL AS 3 machine shows that
the client can ping the opposing network interface regardless of
ip_forward being active or inactive.



Additional info:

I may be missing the point here:
Is there a switch in /proc/sys/net/ipv4/ to mask interfaces from icmp
echo requests (other than /proc/sys/net/ipv4/icmp_echo_ignore_all) and
subsequent network traffic for a multi-homed machine
that is NOT configured as a router and thus provide the same results
as the RHL 7.3 tests?