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Re: [LUG] TCPIP over PPP problems

 

On 27 May 2015 21:26, "Rob Beard" <rob@xxxxxxxxxxxxx> wrote:
>
> Hi folks,
>
> I'm working on a project for work where we want to have a slow link between two sites across a road (with a few trees in the way) to capture a JPG image from a Raspberry Pi every minute. Eventually the site will have some decent network connectivity (probably fibre to our main building) but in the mean time it's a building site so we don't want to risk laying fibre and then having a digger go through it.
>
> The solution I've come up with is two Raspberry Pis (older model B that we had kicking around) with a Slice Of Radio module on each one. For those of you who aren't familiar with it, the Slice Of Radio module basically converts the serial connection on a Pi to RF (800 and something MHz I think) and on other Pi it converts it back to serial. In a way it's like a null modem connection over RF (at a whopping 115200 bps).
>
> So I've managed to get the Pis to talk to each other via serial. I've configured PPP on each Pi and they can connect to each other and I can ping each Pi (with IP forwarding enabled I can also ping the Internet and do DNS lookups over the RF connection). However when I try and grab something over HTTP this is where it falls flat on it's face.

Do you *need* to have PPP in your setup? Could you not set up a separate IP range (say 172.16.1.1 and 172.16.1.2) on the Pi's SoR ttys and simply route traffic through them appropriately using iptables? Or are you doing this so the Ethernet attached to one Pi appears to be in the same subnet as (and so communicates effortlessly with) the Ethernet devices on the LAN that the other Pi is attached to? If you can get your Layer 2 connecting fine, would bridging the relevant interfaces not work?

Grant

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