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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal>This is a follow-up to my previous post on trying to run Heterodyne from a MacBook laptop remotely connected to Metis. It’s working now (though bandwidth limited), so I want to document what I did.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>The Mac communicates via wifi link through a wireless router to an Ubuntu system. The Ubuntu system has a wired Ethernet connection to Metis, on a separate subnet from the one used on the wireless interface. I set up IP forwarding in the Ubuntu system and the Mac (see for details), to enable IP connectivity in both directions from the Mac to Metis. This was confirmed with ping, but something more is needed to run SDR software that communicates with Metis.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Metis must be “discovered” by the SDR app using the pre-defined discovery protocol. This protocol relies on the Link layer (e.g. Ethernet in this case) in such a way that the SDR processor and Metis must be on the same LAN segment. This does not mean just the same IP subnet; there must be no routers between the two systems, as routers do not pass broadcast frames, which are the frames that contain the discovery protocol packets.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Ubuntu supports “bridging” between two Ethernet interfaces, which means that the software establishes a Link layer connection that makes the two interfaces behave as if they are on the same LAN segment. This means they should pass broadcast frames. I tried two documented approaches for doing this, and in both cases, the broadcast frames were not transferred across the bridge. I don’t know if this is a bug in Ubuntu, or if I did it wrong, but I gave up trying in favor of a hardware solution. My failed attempt using Ubuntu is documented here: <a href="http://ubuntuforums.org/showthread.php?t=1906359">http://ubuntuforums.org/showthread.php?t=1906359</a><o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>For the hardware solution, I purchased a used wireless router for $10 that is capable of running DD-WRT firmware. I used a Linksys WRT54G, but any wireless router than runs DD-WRT should work. I connected the Linksys wired ports (i.e. the LAN side) to the Ubuntu system and to Metis. I configured the DD-WRT firmware to operate in “client bridge” mode. In this configuration, the Linksys router connects wirelessly to the wireless router that is connected to my ISP, and bridges its wired ports into that LAN. In this way, the two routers are bridged together as if they were on the same LAN segment. Instructions for configuring a DD-WRT device to run in “client bridge’ mode can be found here: <a href="http://www.dd-wrt.com/wiki/index.php/Client_Bridged">http://www.dd-wrt.com/wiki/index.php/Client_Bridged</a><o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>With this configuration, the broadcast packets go all the way through from the Mac laptop to Metis, and Heterodyne works, although only at the lowest sample rate (48,000 sps). Both wireless routers are running the older 802.11g protocol, and one of them (the one connected to the ISP) has to split its bandwidth, as it simultaneously receives packets from Metis and forwards them to the MacBook. Nevertheless I’m surprised that the app is bandwidth-limited in this configuration. I tried a separate wireless router made by Rosewill with similar results. I will post a separate message with some details about observed behavior and measured bandwidth, and related questions.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Mark – K4XML<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>