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Date:      Wed, 28 Oct 1998 12:34:33 +0000
From:      "Nick A. Fikouras" <nick@dcs.shef.ac.uk>
To:        "freebsd-questions@FreeBSD.ORG" <freebsd-questions@FreeBSD.ORG>
Subject:   Routing table problem
Message-ID:  <36370F58.C6735D95@dcs.shef.ac.uk>

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Hi,

I have three freebsd-2.2.2 machines with two ethernet cards each. Each
machines is connected with each other with an Ethernet link. All
interfaces have IP addresses that belong to the same subnet (say:
255.255.252.0).
The task is: when machine A is having a connection with machine B then
traffic from AtoB should use their direct route while traffic from BtoA
should use the route with the intermediate router C.


A

ep1/    \ep0

/        \
                                                                    vx0
/vx1 vx1\ vx0

B ------- C

Now, the problem is: when I boot up cleanly, A and C can "see" each
other. I know because they can ping each other. It is noted that A and C
are inteconnected through their link#1 (ep0 and vx0). Machines A and B
or B and C can not see each other so I add a route from B to A and one
from A to B:

In machine B:
    route add -host A -interface vx0

In machine A:
    route add -host B -interface ep1

with netstat -r I can see that a route has been established to the
corresponding host but under GATEWAY I find the ethernet address of the
interface that was entered as a parameter to the 'route add' command and
not that of the destination node.

Now, the funny part comes. When A pings B, I can observe with TCPdump
that ping requests are received at interface vx0 of node B but it does
not make any replies. This event is observed when either of the machines
(B or A) is initiating the ping.

It looks as if it is a simple routing table problem, but I haven't been
able to get through it for the greatest part of three days.

I would appreciate any comment,

thanks in advance,

nick


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