Forwarding?

[Andrew Ball]

Hello,

I'm preparing to move up to a NetBSD 3.1 machine. As a
temporary measure, I have connected the new machine to my
existing one via a serial cable and (with help! :-) built
a SLIP connection between them...

,--------------, ,--------------,
| tinman | | almond |
| ~~~~~~ | | ~~~~~~ |
| 192.168.0.129|--rs232--|192.168.0.128 |
| | | 192.168.0.254|--10baseT--> to NAT
`--------------' `--------------' gateway

...my existing machine, almond, has a 10baseT card and
is connected to the Internet via a (non-NetBSD) NAT gateway.

What is the cleanest, simplest way to let tinman share
almond's Internet connectivity? I would like to fetch pkgsrc
and start building a comfortable place to live. I looked in
the NetBSD Guide, but it seemed to point towards NAT on
almond, which feels like overkill.

Any thoughts or suggestions?

- Andy Ball



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[Marcin Jessa]

Post by Andrew Ball
Hello,
I'm preparing to move up to a NetBSD 3.1 machine. As a
temporary measure, I have connected the new machine to my
existing one via a serial cable and (with help! :-) built
a SLIP connection between them...
,--------------, ,--------------,
| tinman | | almond |
| ~~~~~~ | | ~~~~~~ |
| 192.168.0.129|--rs232--|192.168.0.128 |
|
| | | 192.168.0.254|--10baseT--> to NAT
`--------------' `--------------' gateway
...my existing machine, almond, has a 10baseT card and
is connected to the Internet via a (non-NetBSD) NAT gateway.
What is the cleanest, simplest way to let tinman share
almond's Internet connectivity? I would like to fetch pkgsrc
and start building a comfortable place to live. I looked in
the NetBSD Guide, but it seemed to point towards NAT on
almond, which feels like overkill.
Any thoughts or suggestions?

You could set up VLAN between them and use the IP of almond's VLAN end as
tinman's default gw.

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[Hubert Feyrer]

Post by Andrew Ball
Any thoughts or suggestions?

With that setup, you can use proxy arp ("arp -s") to make tinman appear to
be on the ethernet, with almond answering any ARP queries ("what is the
MAC address of tinman?"), and then getting the packets for tinman. almond
just needs to have a route to forward those packets to tinman,
and I guess vice versa.

Such setups are pretty uncommon these days, which is why this is not
documented. Here's a very old document that has a few words about it:
http://www.feyrer.de/Texts/Own/NWF/nwf_69.html#SEC69


- Hubert

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[Martin Husemann]

Probably the easiest way is to set up NAT (network address translation) on
the gateway and treat the host behind the slip link just like your regular
LAN.

Martin

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[Hubert Feyrer]

Post by Martin Husemann
Probably the easiest way is to set up NAT (network address translation) on
the gateway and treat the host behind the slip link just like your regular
LAN.

How is that easier?
It introduces all the NAT problems, needs a seperate management of IP
addresses, you can't directly address the host and its services, etc.


- Hubert

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[Herb Peyerl]

Post by Martin Husemann
Probably the easiest way is to set up NAT (network address
translation) on
the gateway and treat the host behind the slip link just like your
regular
LAN.

No, hubert's right. If he can get proxyarp working, then that's the
right answer. I've only ever done it with ppp though.


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[Andreas_Hallmann]

Post by Andrew Ball
Hello,
I'm preparing to move up to a NetBSD 3.1 machine. As a
temporary measure, I have connected the new machine to my
existing one via a serial cable and (with help! :-) built
a SLIP connection between them...
,--------------, ,--------------,
| tinman | | almond |
| ~~~~~~ | | ~~~~~~ |
| 192.168.0.129|--rs232--|192.168.0.128 |
| | | 192.168.0.254|--10baseT--> to NAT
`--------------' `--------------' gateway
...my existing machine, almond, has a 10baseT card and
is connected to the Internet via a (non-NetBSD) NAT gateway.

You have choosen static ip numbers.
So you don't need proxy-arp.

Configure almond as a router.

Tell tinman, that it's default route has next hop almond.
Tell almond the static route to tinman.

Either activate routed on almond and let almond and your nat-box exchange routing information via RIP or RIPv2.

Or Tell your nat-box statically, that the next hop to tinman is almond.

I prefer the rip-solution, since network tend to grow once you have started.
You already have two routers in your setup. Adding a third will start a growing
static route conplexity. Maybe you like to add a backup-route to internet via (nowadays cheep) isdn or modem router? Them dynamic routing will switch from your standard route to backup automatically for you. Nice isn't it?

Andreas

[der Mouse]

I'm preparing to move up to a NetBSD 3.1 machine. As a temporary
measure, I have connected the new machine to my existing one via a
serial cable and (with help! :-) built a SLIP connection between
them... [tinman SLIP to almond 10baseT to NAT to world]
What is the cleanest, simplest way to let tinman share almond's
Internet connectivity?

My money would be on using proxy arp. Create a proxy arp entry on
almond for tinman's IP, and set tinman's default route to point to
almond's end of the SLIP link, and it should all Just Work.

I would like to fetch pkgsrc

Over a serial line? I hope you have lots of patience. Even if you're
using a baudrate like 115200, that'll take a long time.

I looked in the NetBSD Guide, but it seemed to point towards NAT on
almond, which feels like overkill.

I agree.

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[Andrew Ball]

Hello Mouse,

dM> My money would be on using proxy arp. Create a proxy

arp entry on almond for tinman's IP, and set tinman's
default route to point to almond's end of the SLIP
link, and it should all Just Work.

I get...

almond# arp -s tinman 00:10:4b:a5:ba:5b pub
cannot intuit interface index and type for tinman
almond# arp -s 192.168.3.129 00:10:4b:a5:ba:5b pub
cannot intuit interface index and type for 192.168.3.129

ASB> I would like to fetch pkgsrc

dM> Over a serial line? I hope you have lots of patience.

Even if you're using a baudrate like 115200, that'll
take a long time.

Until recently I was fetching it over a V.34 analogue modem,
so 115,200 BpS is a step up :-)

- Andy.


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[der Mouse]

Post by Andrew Ball

Post by der Mouse
My money would be on using proxy arp. Create a proxy arp entry on
almond for tinman's IP, and set tinman's default route to point to
almond's end of the SLIP link, and it should all Just Work.

I get...
almond# arp -s tinman 00:10:4b:a5:ba:5b pub
cannot intuit interface index and type for tinman
almond# arp -s 192.168.3.129 00:10:4b:a5:ba:5b pub
cannot intuit interface index and type for 192.168.3.129

Either 192.168.3.129 is not on-subnet for almond's Ethernet, and the
address tinman resolves to isn't on-subnet either, or someone has
broken proxy arp in the version you have.

Your initial email shows almond has having 192.168.0.254 on its
Ethernet, with no subnet mask specified and thus probably a /24, and
tinman at 192.168.0.129 (not .3.129). Tinman's address needs to be
on-subnet for almond's Ethernet for the proxy arp method to be possible
at all. (In passing, I would recommend that almond's end of the SLIP
link use the same address that almond's Ethernet does, though this is a
comparatively minor issue.)

Post by Andrew Ball

Post by der Mouse

Post by Andrew Ball
I would like to fetch pkgsrc

Over a serial line? I hope you have lots of patience. Even if
you're using a baudrate like 115200, that'll take a long time.

Until recently I was fetching it over a V.34 analogue modem, so
115,200 BpS is a step up :-)

Heh. Yes, I guess it is. :-)

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[Andrew Ball]

Hello Mouse,

dM> Either 192.168.3.129 is not on-subnet for almond's

Ethernet, and the address tinman resolves to isn't on
-subnet either, or someone has broken proxy arp in
the version you have.
Your initial email shows almond has having
192.168.0.254 on its Ethernet, with no subnet mask
specified and thus probably a /24, and tinman at
192.168.0.129 (not .3.129).

That's my fault. When I first set up the link, my hope was
to have the link between tinman and almond as part of the
same subnet (192.168.0.n/24) as the 10baseT LAN that almond
connects to. To make SLIP work, I eventually moved to
192.168.3.n/24.

Mihai Chelaru has very kindly provided an ipnat setup that
enables tinman to access the Internet via almond. I have yet
to invest the time needed to wrap my head around how this
works. I may set up another machine with SLIP using the same
subnet as the LAN so that I can have another go at proxy-arp
without breaking tinman's current configuration.

- Andy Ball


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[Andrew Ball]

Hello Hauke,

HF> http://la.causeuse.org/hauke/slip/ has some

information, including a proxy-arp setup. I should
probably go and fill in the gaps.

Sadly that link doesn't work for me (404). proxy-arp would
seem to make sense, since the neither end of the SLIP link
will have an Ethernet MAC address. The SLIP link is working
well, but I'm not sure how to connect the interfaces.

- Andy Ball


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