[nos-bbs] tun0 and more Linux routing commands

[Maiko Langelaar]

Bill,

> It appears the JNOS startup creates the TUN0 interface, which is then
> configured back in the linux world with the shell ifconfig command.

Correct, that gives a basic route between JNOS and LINUX. Depending on
what distro you are running, it would be wise to use the full pathname
to the 'ifconfig' linux command.

> /bin/modprobe tun

On any redhat based system I've used, that is automatic. Otherwise
you could put the command in the rc.local file.

> echo "1" > /proc/.../enable_forwarding

You mean this one below :

    echo 1 >/proc/sys/net/ipv4/ip_forward

Only needed if you want clients on your linux LAN to reach JNOS and
back. Without it, packets will not traverse between eth0 and tun0
on your linux box, and they will never reach JNOS then.

> And finally, so the Linux box responds to arp requests for the JNOS box.
> # Proxy ARP for jnos2 port of local LAN
> # $ARP -s 192.168.27.12 00:0d:60:29:56:bb pub

I've never understood this need for ARP that I see so many times. Is this
something from the old days ? I've never used it. If I am on a particular 
Winxp on my LAN, I simply do 'route add 192.168.1.201 192.168.1.60' on the
particular PC, and I can telnet, browse, whatever to my JNOS. In the above
example route, JNOS=192.168.1.201 and LINUX(running JNOS)=192.168.1.60.

Can anyone educate me on why I see so many people putting this arp thing 
in ? Is there some functionality that I am missing out of this ?

Maiko