SUMMARY: ip-forwarding problem in gateway

From: Heo Sung Gwan (heo@cslsun10.sogang.ac.kr)
Date: Mon Mar 04 1996 - 22:34:52 CST


My question is :

 Hi. I have some trouble with setting up the gateway. So I ask your help.
 We have 30 new SUN workstations and will connect them to the our school's LAN.
 So I have the plan to make one of 30 machines a gateway.

 Our school network is 163.239.0.0 and new subnetwork for 30 new machines is
 163.239.150.0. And the gateway has two ip addresses - 163.239.150.210 and
 163.239.130.41. le0(163.239.150.210) is connected to hub to which all other
 new machine is connected. le1(163.239.130.41) is connected to hub through
 which the gateway can reach school's LAN.
 
 First the summary of my environment follows :

                            gateway hub
          hub 163.239.130.41 ----
          ---- |--| | |-----
          | |---------------|__|-------------| | |--|
 ---------| | 163.239.150.210 | |---------|__|
 to our | | ---- 163.239.150.212
school's | |-------------------------------------
LAN ---- |
                            | 163.239.130.50
                           |--|
                           |__|

 * I run SunOS 4.1.3 on all machines.

 * At gateway, I can 'telnet 163.239.150.212' and also 'telnet 163.239.130.50'.
 
 * But at 163.239.150.212, I can't 'telnet 163.239.130.50' and at 163.239.130.
  50, can't 'telnet 163.239.150.212'.
 
 * Therefore I supposed that the gateway failed to do ip-forwarding.
   That is true :
    gateway $ netstat -s
                  .
                  .
                0 packets forwarded
                5001 packets not forwardable
                  .
                  .
   So I checked the kernel variable, ip-forwarding, but it is set to 1.
    gateway $ adb -k -w /vmunix /dev/mem
               ip_forwarding?
               ip_forwarding 10000

 * And then check the routing tables and netmasks :
    gateway $ cat /etc/netmasks
              163.239 255.255.255.0
    

   1. Routing table of gateway :
            Dest Gateway Flags Interface
      127.0.0.1 127.0.0.1 UH lo0
      163.239.130.0 163.239.130.41 U le1
      163.239.150.0 163.239.150.210 U le0
     (These is set by routed(?) when booting)

   2. Routing table of one of other machines, 163.239.150.212 :
            Dest Gateway Flags Interface
      127.0.0.1 127.0.0.1 UH lo0
      163.239.130.0 163.239.150.210 UG le0
      163.239.150.0 163.239.150.212 U le0
   
   3. Netmask of each interfaces of each machines?
            IP address netmasks
       163.239.150.210 255.255.255.0 - le0 of the gateway
       163.239.130.41 255.255.255.0 - le1 of the gateway
       163.239.150.211 255.255.255.0
       163.239.150.212 255.255.255.0
              . .
              . .

 
 * And 2 interfaces are up :
   gateway $ ifconfig -a
           le0: flags=63<UP,BROADCAST,NOTRAILERS,RUNNING>
            inet 163.239.150.210 netmask ffffff00 broadcast 163.239.150.0
           le1: flags=63<UP,BROADCAST,NOTRAILERS,RUNNING>
            inet 163.239.130.41 netmask ffffff00 broadcast 163.239.130.0
           lo0: flags=49<UP,LOOPBACK,RUNNING>
            inet 127.0.0.1 netmask ff000000
 
 Why the gateway does not forward packets ?
 What is wrong?

 
The answer is :

 I shoud have had the following routing entry in 163.239.130.50.

         Dest Gateway Flags Interface
      127.0.0.1 127.0.0.1 UH lo0
      163.239.130.0 163.239.130.50 U le0
   * 163.239.150.0 163.239.130.41 UG le0
          
 The problem is in 163.239.130.0 network.

Thanks to all who responded :
 
 Robert Sessions <robert@pwl-sparc2.pwl.com>
 Venkata Ramakrishn <ramu@duettech.com>
 John Justin Hough <john@oncology.uthscsa.edu>
 Cheryl L. Southard <cld@astro.caltech.edu>
 Bismark Espinoza <bismark@alta.jpl.nasa.gov>

Good day Everyone !!!

-------------------------------------
E-mail : heo@cslsun10.sogang.ac.kr



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