On 22/04/13 10:20 AM, James Harper wrote:
Mostly replying via the Russell's post to the OP...
If you know a bit about OSPF (or RIP) and can arrange a router at each end then yes, easily. That's likely to cause other issues, since broadcasts won't propagate across the network (good way to screw up applications that rely on broadcasts). I know there are a couple that would need to operate across the link.
If you have a proper wireless bridge at each end and can run Linux bridge at each end to bridge the two interfaces (wifi and powerline) and turn on STP then also yes, easily. That's one for the future
My laptop has "LAN/WLAN switching" so that if I plug a network cable in the wireless switches off, which saves a heap of DHCP addresses when you consider 100 laptops on a single network. If your far end machine has that sort of capability then it would work in the "Ethernet link down" case, but not if there was some other fault that still presented a link connected without actually having end to end connectivity. If your far end machine runs linux then a simple ping script to swap over might be easiest. I think the Ethernet link stays up if the powerline connectivity is lost. The rest would only work is there was a Linux box directly connected to both interfaces (there won't be, there will be a switch).
If it were me, I'd get a couple of openwrt based devices (netgear wndr3800's are what I've been using lately) and create separate /30 networks over each of the wireless and powerline links, then use OSPF to route over whichever one has connectivity, giving the powerline link priority if that has the better performance. Of As above, not the ideal case, there are a couple of applications used across the network occasionally that rely on being in the same broadcast domain (Bonjour based, etc). course that doesn't work if you need the same broadcast domain, in which case I'd bridge them and use STP, but I'm less familiar with that. Also, that doesn't necessarily handle the case where powerline link is up but performing badly etc. I've only had all or nothing performance in the past, but I don't think there is any hardware indication of link failure (i.e. the connected device still sees a link active), it simply looks the same as if you were plugged into a dumb switch with nothing else connected to it.
-- 73 de Tony VK3JED http://vkradio.com