Token-Ring to Ethernet IP routing fails

[John Garnett]

In article <495 at janus.Quotron.com> todd at janus.Quotron.com (Todd Booth) writes:
>Has anyone got PS/2 AIX to perform IP routing between Token-Ring and
>Ethernet?  I have not been able to and here's my setup:

Yes, I have been able to get an AIX PS/2 machine to route IP packets
between Ethernet and Token Ring.

>
>todd	      psfile	    psfile        
>130.224.5.14  130.224.5.14--130.224.4.14  
>          |   |		     |		  
>          |   |	             |		  
>        +-+---+-+            |		  
>    MAU | Token |           (=========================)
>        +-------+           Ethernet
>
>Since psfile is connected to both Ethernet and Token-Ring networks, it
>*should* be able to act as an IP router (as documented in the IBM TCP/IP
>User's Guide).  

true

>
>I've setup todd to use psfile as the default IP gw (router).  From todd,
>I ping 130.224.5.14.  Psfile then sent did a RIP broadcast to 130.224.5.63
>to find 130.224.4.14!  Psfile didn't know that the packet was being sent
>to itself.  Often this would cause psfile's token-ring interface to stop
>accepting rlogin's although it would respond to icmp echo requests.
>

Unless you are using an appropriate subnetmask, the problem lies with
the IP addresses you are using.  Both 130.224.5.14 and 130.224.4.14
are on the same Class B network address 130.224.  Each network adapter
in a given machine needs its own distinct network address.  By 
default, Class B addresses use ff.ff.00.00 as the subnetmask.
Applying this mask to both of your addresses gives the same
network address of 130.224.  (you can use explicit subnetmasks to 
make 130.224.5.14 distinct from 130.224.4.14 - i.e. ff.ff.ff.00).  

Also, each machine on the token ring with need a route to point it
to its default gateway.  One way to do this is to add the following
route to all token ring machines:

route add 0 130.224.5.14 1

On all Ethernet machines, use:

route add 0 130.224.4.14 1

the best place to put these routes is in /etc/rc.tcpip

Finally, you should also make sure that you have a different host
name (in /etc/hosts) for each address of the bridge.  This is 
necessary so that the "ifconfig" commands in /etc/rc.tcpip will be able
to correctly configure the token and ether adapters.  You will
need to add an ifconfig statement to /etc/rc.tcpip for the Ethernet
card (the one for token [tk0] should already exist).

-- 
+------------------------------------+-----------------------------------+
| John Garnett                       |      Base 1.9                     |
| garnett at rpp386.cactus.org          |                                   |
| {bigtex|texbell}!rpp386!garnett    |      "It's almost binary"         |