Re: Getting slip(4) to work beyond two machines

[Johnny Billquist <bqt%update.uu.se@localhost>]

On 2020-03-10 21:45, Björn Johannesson wrote:
> Hello.
>
> I'm trying to connect two machines via slip(4) and then get communication going outside those two.
> One of the machines have a NIC and I wan't to get the machine behind that one to reach outside.
> I have done this once long ago and I had jotted down these notes: https://pastebin.com/UK43aV5x
> I'm trying to get this working on again now. IP's have changed ofc.
>
> On the machine w/o NIC I do:
> ifconfig sl0 create
> slattach -s 115200 /dev/tty00
> ifconfig sl0 inet 192.168.0.51 192.168.0.50
> route add default 192.168.0.50
>
> On the machine with NIC:
> ifconfig sl0 create
> slattach -s 115200 /dev/tty00
> ifconfig sl0 inet 192.168.0.50 192.168.0.51
> arp -s 192.168.0.51 6c:3b:e5:1f:98:d8 pub proxy
> sysctl -w net.inet.ip.forwarding=1
> (The real NIC on this machine has ip 192.168.0.114 netmask ffffff00)
>
> The two machines communicate fine with each other - however the forwarding part does not.
> 192.168.0.51 cannot communicate past .0.50 and cannot be reached from outside .0.50.
> There is also a _significant_ delay when communicating from .51 to .50 after adding the "route" command.
> If I ping .50 from .51 it takes many seconds (>10) before it starts sending packets.
>
> What am I missing?
> Please CC for reply.

The delays are most probably because DNS timeouts.

As for reachability, .50 will assume it can directly reach anything on 
192.168.0. It won't use the default router for those.
Might be that you can make that happy by setting a really narrow netmask?

Any other machine on your local network might be able to reach .50, 
since you have proxy arp setup. So it might only be an issue on the .50 
side...?

  Johnny

--
Johnny Billquist                  || "I'm on a bus
                                  ||  on a psychedelic trip
email: bqt%softjar.se@localhost             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol