Getting slip(4) to work beyond two machines

[Björn Johannesson <rherdware%yahoo.com@localhost>]

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.

/B