SUMMARY : interesting IP problem

From: Vasu Vuppala (
Date: Tue Jun 24 1997 - 23:45:55 CDT

Here is the original posting :

> I've a sparc-20 (running Solaris 2.5.1) with two network interfaces
> le0 and le1. The two interfaces are connected to different LANs and
> have the IP addresses (le0) and (le1).
> netmask is The LANs are connected by a router.
> I have a program running on this machine which sends UDP packets from
> to I want the packets to go out through
> le0,
> go through the router and come back through le1. I tried various
> things
> with the routing table but no use. The packets never go out on the
> LANs
> because IP figures out that is a local interface and
> loops
> the packets back.
> Is there any way to do this ?

Summary :

I got a lot of suggestions, many of which I had already tried and the others
did not work. Here is a list of things which were tried (in conjuction and
various combinations)

      * disabling ip_forwarding (ndd -set /dev/ip ip_forwarding 0)
      * removing the local network routing table entry for le1 that is
        added during the ifconfig invocation
      * adding a routing table entry for through le0 (via the
        router or via
      * making a (host) routing entry to through le0
      * making default route go through le0
      * removing localhost routing entry
      * setting a large metric value for le1 using ifconfig
      * setting large metric value for the routes through le1

I find that the problem has to do with the following entry (gotten
with 'netstat -nra' )

  Destination Gateway Flags Ref Use Interface
-------------------- -------------------- ----- ----- ------ --------- -- UHL 0 14 le1

There is no way to remove it. Even if I could remove it packets coming
in through le1 probably will not be accepted ! So looks like there is no
way to do it. If someone has more insight into this please let me know.

Thanks to:

"Stevan P. Meck" <>
Ing._Erick_Cedeņo <> (Charles Gagnon)
Tom Vayda <>
"Liu, Micky (DTSI)" <>
"Phil J. DuLong" <>
adnan dzinic <>
bismark@alta.Jpl.Nasa.Gov (Bismark Espinoza)
"Bruce S. Jurilla" <>

- vasu

This archive was generated by hypermail 2.1.2 : Fri Sep 28 2001 - 23:11:57 CDT