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Old February 4th 06, 10:10 PM posted to rec.radio.amateur.digital.misc
 
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Default Can't run TCP/IP through AX.25 using Linux

Hi Bob,

I compiled net-tools on the slug and I now get this, which looks much
better:
root@slug:~# ifconfig ax0
ax0 Link encap:AMPR AX.25 HWaddr VA2JF-2
inet addr:172.25.25.2 Bcast:172.25.255.255 Mask:255.255.0.0
UP BROADCAST RUNNING MTU:1500 Metric:1
RX packets:52 errors:0 dropped:0 overruns:0 frame:0
TX packets:22 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:10
RX bytes:4238 (4.1 Kb) TX bytes:898 (898.0 b)

net-tools also provided a version of arp. When I use it, though, I get
this strange behavior:
=====
root@slug:~# arp -an
? (192.168.0.5) at 00:01:53:80:57:E6 [ether] on eth0
root@slug:~# arp -H ax25 -i ax0 -s 172.25.25.1 VA2JF-1
root@slug:~# arp -an
? (172.25.25.1) at * [ax25] PERM on -
? (192.168.0.5) at 00:01:53:80:57:E6 [ether] on eth0
root@slug:~# cat /proc/net/arp
IP address HW type Flags HW address Mask Device
172.25.25.1 0x3 0x6 * ax0
192.168.0.5 0x1 0x2 00:01:53:80:57:E6 * eth0
=====
I'm not sure if this is related to my version of arp or the kernel but
I have a feeling that this is at the heart of the problem...

If you arent intent on using busybox you may want to try the Knoppix
run from CD version that has the amateur radio add-ons.


The slug is in fact a NSLU2 from Linksys, which is not much bigger than
my hand. There's no CD player on this, so I'm stuck with busybox if I
want to use the NSLU2. http://xrl.us/NSLU2

re PPP and HDX/FDX. Well in a way you are simply shifting the HDX
switching back to the computer instead of using the radio hardware.
I'd suspect that in the end you wouldnt do any better. I am however
prepared to be shot down over this!


When working in FDX simulation, the radio hardware does the HDX
switching 50:50. This is fixed and cannot be changed. I hope that AX.25
will switch it dynamically, sometimes 90:10 sometimes 70:30, so that I
can get better performance when I need it. I'm not sure if it's worth
the trouble, however.

I have an application of sorts for this same mind of thing. My mother
in law lives about 500 yards away just over the brow of a hill. There
are also lots of trees! I doubt 2.4GHz will work and was looking at
something with at least 115K throughout to connect her PC to our
network. What has been your experience with the 900MHz gear and how
well does it do with path obstacles? Oh and what did the units cost?


I bought the Connexlink radios a couple months ago from Mouser. I
bought the starter pack (Includes 1 server and 1 client Unit, RS-232
cables, Antennas, Power Supplies and Software) for US$225 (Mouser Stock
No. 814-CL4490-232-SP). About 1 week after ordering, I got a phone call
from a ConnexLink technician asking for informations about my project
and giving me his phone number if I needed any help.

My link is similar to yours, it's to my mother's house and I'm afraid
that 2.4 GHz is not going to cut it unless I install a 100' tower on
each side. It's 2.9 Km long (1.8 miles). I have a hill and lots of
trees doing obstruction. Take a look at my path profile, I'm about at
F0.9. It's made with Radio Mobile:
http://www.cplus.org/rmw/english1.html

Path profile scaled 10:1:
http://guillaume.filion.org/80211lin...l-900-10-1.gif

Path profile not scaled (1:1):
http://guillaume.filion.org/80211lin...el-900-1-1.gif

I haven't tested the hardware outside yet -- it's winter time here and
I don't feel like climbing on the roof top full of snow. The specs says
it can do 32 Km LOS with the stock antennas. I'm not LOS, but with yagi
antennas replacing the stock antennas, I'm pretty sure that I could
have a decent link.

Common wisdom says that 900 MHz is too crowded for any good use, but I
live in the country and there is not a lot of 900 MHz activity around
here. The ConnexLink uses Frequency Hopping Spread Spectrum so it's
more resistant to QRM. Your mileage may vary...

Some links:
http://www.mouser.com/aerocomm/
http://www.aerocomm.com/Devices/link.htm

73
GFK's
--
Guillaume Filion, ing. jr
Logidac Tech., Beaumont, Québec, Canada - http://logidac.com/
PGP Key and mo http://guillaume.filion.org/