Bug 119421 - unexpected routing on multi-homed RHEL AS 3 machine
Summary: unexpected routing on multi-homed RHEL AS 3 machine
Alias: None
Product: Red Hat Enterprise Linux 3
Classification: Red Hat
Component: kernel (Show other bugs)
(Show other bugs)
Version: 3.0
Hardware: i686 Linux
Target Milestone: ---
Assignee: David Miller
QA Contact:
Depends On:
TreeView+ depends on / blocked
Reported: 2004-03-30 10:30 UTC by Roger Nunn
Modified: 2007-11-30 22:07 UTC (History)
2 users (show)

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of:
Last Closed: 2004-04-03 22:19:01 UTC
Type: ---
Regression: ---
Mount Type: ---
Documentation: ---
Verified Versions:
Category: ---
oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---

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Description Roger Nunn 2004-03-30 10:30:14 UTC
From Bugzilla Helper:
User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.5a)
Gecko/20030728 Mozilla Firebird/0.6.1

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):

How reproducible:

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

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?

Comment 1 Ernie Petrides 2004-03-31 20:34:44 UTC
Kernel version 2.4.9-e.38 refers to RHEL AS 2.1, not 3.  Could you
please confirm which information is correct, the kernel version or
the release you've specified?  (I've tentatively changed the bug's
product version and added our 2.1 maintainter to the cc: list.)

Thanks.  -ernie

Comment 2 Roger Nunn 2004-03-31 21:36:15 UTC
many apologies, the kernel version should reflect:
The version of Red Hat displaying the problem is RHEL ES version 3
I have reverted the version accordingly.


Comment 3 Ernie Petrides 2004-03-31 23:17:14 UTC
Ok, thanks.  -ernie

Comment 4 David Miller 2004-04-03 22:19:01 UTC
This is expected behavior.

When the kernel sends a packet out, it checks whether the destination
is an address assigned to one of the systems interfaces.  If so, it simply
passes the packet over the loopback interface and receives it, it never
actually goes onto the physical network.

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