Re: Serial SLIP Connection

[Greg Troxel <gdt%lexort.com@localhost>]

Dan Plassche <boomer3200%gmail.com@localhost> writes:

> On 11/1/18, Andy Ruhl <acruhl%gmail.com@localhost> wrote:
>> On Thu, Nov 1, 2018 at 10:50 AM Dan Plassche <boomer3200%gmail.com@localhost> wrote:
>>> ifconfig sl0 inet 10.0.2.7 10.0.2.6 arp up
>>> route add default 10.0.2.6
>>>
>>> 5. Setup interface on server
>>>
>>> ifconfig sl0 create
>>> slattach -l -s 9600 -t slip /dev/tty00
>>> ifconfig sl0 inet 10.0.2.6 10.0.2.7 arp up
>
> Thanks, Andy.  The netmask was defaulting to 255.0.0.0 and I now
> set it to 255.255.255.252 at each end.  I tried again without cu
> and setting both ends as 10.0.5.1 and 10.0.5.2, but still had the
> same behavior (can ping out, but no packets received or route to
> DNS on the cient). The test server's network card is at 10.0.2.15
> with the gateway at 10.0.2.2 and the DNS at 10.0.2.3.  Adding
> additional static routes to those endpoints through the NetBSD
> server did not seem to help.

I am not really following your descriptions of what is working and what
isn't, in particularly "ping out".

On the two machines with slip, you should run tcpdump, and on each, see
what happens when you "ping -n 10.0.5.2" from 1, and vice versa.  If
that works, your slip configuration itself is ok.

Then, on the machine that has a regular interface and slip (yes, an old
timer is cringing hearing that :-), presumably you can successfully ping
machines on the greater internet, telnet to 80/443, etc.

Then, the questions are:

  is IP forwarding enabled on the gateway machine?

  if you ping 10.0.2.2 from the slip-only machine, and run tcpdump on
  the gateway machine, first on the slip line, and then on the ethernet,
  do you see the outgoing ICMP echo request packets?  Do you see
  replies?

  run netstat -s, then do the above for 10s, then netstat -s again, and
  diff the results.  Explain all changed counters.  (Really; this will
  find things you don't realize you should look for.)

  on another machine on the lan, ping 10.0.5.2.  tcpdump and see what
  happens.  Explain how you have routes set up for normal lan machines
  to know that 10.0.5.0/30 is reached via the gateway machine.