Re: how to "join" LAN with plip link?

Hello. Thank you very much for giving me very detailed answer last time
over the plip/proxy-arp topic. For the last serveral days I have been
trying to dig through documents and figure out how to configure a
proxy-ftp and would like to later write an aritcle (or complement
current
PLIP howto) about a real case on how I have made a plip connected host
looking like on the LAN.

However I still didn't successfuly set it up. There are many steps so I
worry maybe some steps I have made wrong, thus here is what I did:

I set up my network this way:


1) setup plip0
host joe.realss.com (SuSE 10.2) has NIC with address 218.193.55.195,
plip0 with address 218.193.55.195 pointopoint 218.193.55.210
host quasimodo.realss.com (FreeBSD 6) has only plip0 with address
218.193.55.210 pointopoint 218.193.55.195

Now ping from host joe to host quasimodo works, ping from host
quasimodo to host joe works.

2) setup proxy-arp
on host joe.realss.com do:

# modprobe iptable_filter
# echo 1 > /proc/sys/net/ipv4/conf/eth0/proxy_arp
# echo 1 > /proc/sys/net/ipv4/conf/plip0/proxy_arp
# echo 1 > /proc/sys/net/ipv4/ip_forward

All commands run without error message. Then I test the proxy-arp by
using a third host: exupery.realss.com which is 218.193.55.198. I ran a
test on exupery.realss.com
[zhangweiwu@exupery ~]$ arp 218.193.55.210
? (218.193.55.210) at 00:0f:ea:4b:82:58 on fxp0 [ethernet]
[zhangweiwu@exupery ~]$ arp 218.193.55.195
? (218.193.55.195) at 00:0f:ea:4b:82:58 on fxp0 [ethernet]

The result seems to suggest arp proxy is actually running (because the
NIC of joe.realss.com reports it has two IP address)

3) set up route

I don't change the route on joe at all, because I think nothing needs to
change.
zhangweiwu@joe:> netstat -r
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
218.193.55.210 * 255.255.255.255 UH 0 0 0 plip0
218.193.55.0 * 255.255.255.0 U 0 0 0 eth0
loopback * 255.0.0.0 U 0 0 0 lo

i changed route on quasimodo.realss.com to let it use plip0 to access
other hosts on LAN
# route add 218.193.55.0 -netmask 255.255.255.0 -iface plip0
add net 218.193.55.0: gateway plip0

Test on quasimodo:
# ping 218.193.55.198
[time out]

Test on exupery:
# ping 218.193.55.210
[time out]

Looks like packets are not forwarded or /proc/sys/net/ipv4/ip_forward
simply doesn't work.

so how should I go on from here?



Moe Trin (ibuprofin@xxxxxxxxxxxxxxxxxxxxxx) 2006/12/26 06:46
On 25 Dec 2006, in the Usenet newsgroup comp.os.linux.networking, in article
<4v96b5F1ag7v8U1@xxxxxxxxxxxxxxxxxx>, Zhang Weiwu wrote:

Hello. I have successfully connected two computers through plip0 (don't
know if current speed of 3kB/s is reasonable).

-rw-rw-r-- 1 gferg ldp 46049 Apr 26 2001 PLIP

That's a mini-howto, and section 1 states:

The speed achieved depends completely on your hardware (CPU and
parallel port) and system load, in general it may be from 5 Kb/sec up
to even 40 Kb/sec.

but you may also want to have a look at the "Linux Network Administrator's
Guide" (nag2 at any LDP mirror, or http://tldp.org/guides.html). It has a
whole chapter on PLIP.

The 'server' has a parallel port and is connected to LAN, the 'client'
have a parallel port and is not connected to LAN, I guess this is typical.
Now how can I make this 'client' join the LAN?

The nag2 should help. Either you need to configure the "server" as a router,
and have all systems know to send packets to the router as a gateway to the
LAN (or client), or you need to configure the server to do 'proxy-ARP'. In
the first method, the 'client' and LAN hosts would be on different networks
(such as 192.168.1.0/24 for the LAN, and 192.168.2.0/24 for the client),
while the proxy-ARP method would require client and LAN to be on the same
network range. See also

-rw-rw-r-- 1 gferg ldp 19372 Aug 28 2000 Proxy-ARP-Subnet

another mini-howto.

For client to access LAN I need to set up nat on the 'server',

Not really - proxy-ARP is much simpler.
.

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