[TriLUG] help setting up Nextel BPL modem under Linux

[Joseph Mack NA3T]

On Thu, 8 Jul 2004, Aaron S. Joyner wrote:

> Okay, first, to clear up a few misconceptions.  The Nextel service is
> not BPL based.  It's a 3G (3rd Generation) Cellular Network, in other
> words it operates in similar spectrum and off the same towers, as the
> regular Nextel Cellular service does.

I really didn't have a clue, but I'd heard that it was BPL. Thanks

> So don't worry, your 10m band will be fine.  :)

it's 2m or higher for me

> You are precisely correct in that the "broadband modem" you have is just
> a bridge.  Also, if you're using the Static IP based service, you
> *probably* shouldn't be getting your address via DHCP.  You'll need to
> get a gateway address from Nextel that corresponds to your Static IP
> subnet - if I had to hazard a guess I'd bet on 65.76.244.254 or
> 65.76.244.1  Try setting your gateway to one of those addresses, and see
> what you get.

this is probably the usual case, but here you ask for a static IP
and they tell you to dhcp and it comes from the modem, with an
expiration of 60secs. I had assumed it's hardwired into the modem,
but if it's 3G Cellular, I have no idea where the dhcp server is.

> Bottom line, from a purely networking perspective, you can't have a
> default gateway that a) is not on your local subnet or b) you don't have
> a static route to --- and b is really uncommon.

yes, I understand this :-)

> So uncommon that in my 8 years in the ISP industry, I've never seen it
> done.

it may be mathematically impossible

> So let's hazard a guess that your default gateway really is accessible
> on the other side of that connection, and you can send it traffic
> directly.  What you'd need to setup in Linux is something like this: #
> route add -host 172.29.251.133 dev eth0

I can run this command (unlike with the route add default gw command),

> ...Which would give you something like this...
> # route
> Destination     Gateway         Genmask         Flags Metric Ref    Use
> Iface
> 172.29.251.133  *               255.255.255.255 UH    0      0        0 eth0
>
> At which point you'd be able to add 172.29.251.133 as your default gateway.

but I still don't have a route to 172.29.251.133 (can't ping it)
presumably because I don't have that IP in the network of any NIC on my
machine.

> Other, sneaky yet valid, options - try nmap'ing your entire subnet.  See
> what IPs respond, and try setting your default gateway to that IP
> address and pinging out.  :)

when I set up in windows, I can't ping the default gw (or the nameservers
I get from dhcp) even though I can route to the outside world, and can get
name resolution (and nslookup works)

what did you do to configure your setup, just run dhclient?

> Above all, let us know what you come up with - I'd really like to hear.
> Also, if you want further help, I'll be at the meeting tonight w/ my
> working Nextel broadband connection.  :)  The only difference being that
> I don't have the static IP based service.

I did have something else planned this evening, but if I don't get this
running this afternoon, I'll gladly come along. Will you be wearing a red
rose in your lapel and hopping up and down on one foot? I'll bring my
nextel modem, and plug it into your machine if that's OK.

Joe

-- 
Joseph Mack NA3T EME(B,D), FM05lw North Carolina
jmack (at) wm7d (dot) net - azimuthal equidistant map
generator at http://www.wm7d.net/azproj.shtml
Homepage http://www.austintek.com/ It's GNU/Linux!