[nos-bbs] two jnos computers on same lan...

[jerome schatten]

OK... basic connectivity is going!  From machine #1's linux prompt, I
can ping the jnos side of the tun interface on machine #2. And
visa-versa.

Thanks for the xtal clear instructions.

Moving on...

jerome -ve7ass


On Wed, 2013-01-02 at 12:49 -0500, Mark Phillips wrote:
> Forget the JNOS for a minute.
> 
> It would seem that you need a primer in IPv4 subnetting. For the sake
> of the others here I'm not gonna go into it too deeply.
> 
> In a nutshell, a subnet describes the amount of IP addresses reachable
> in the circuit in question (in our case your LAN). Change to a
> different circuit (your TUN device) and you need a different subnet
> for that circuit. A simple way of calculating subnets is to subtract
> the amount of numbers you need/have from 256. So 256-8=248 or
> 255.255.255.248
> 
> 192.168.1.0/24 (255.255.255.0) as found on your LAN would give you 256
> IP's from 0-255 and should all be reachable on your LAN and _not_ via
> devices such as routers or other hosts. The first and last numbers of
> any subnet are always lost to network and broadcast addresses for a
> usable 254 addresses in your case.
> 
> A LAN does not work at the IP layer but rather at the MAC layer (this
> is true for RF as well as wired). Enter Address Resolution Protocol
> (ARP). To reach a given IP address the originating host fires out an
> ARP request to the whole LAN subnet asking for the MAC address of the
> host servicing the IP address it wants to contact. When this request
> is satisfied the originating host then addresses its packets to the
> MAC address rather than the IP address.
> 
> So, in your case you have 2 IP's residing at the other end of a TUN
> link rather than on the LAN where they should be. To solve this issue
> we have to get the servicing hosts to advertise the fact that they
> service the relevant IP address. At the Linux prompt try something
> like "arp -i eth0 -Ds jnos.end.of.tun0 eth0 pub" where
> jnos.end.of.tun0 is the 192.x.x.x IP of the JNOS instance. Test by
> pinging from your desktop PC to one of the JNOS IP's.
> 
> 
> One thing at a time. Get this basic connectivity going and then we can move on.
> 
> Mark
> 
>