[ILUG] PAN0 killing net

[Gareth 'bigbro' Eason]

Ian wrote:
> what do you mean by L2-adjacent ?
[snip]

	While it's not quite a correct use of the term in this case, the
implication is clear - for convenience (and to save routing table space
and computation power) the internet IP space is broken up into networks
and hosts - so:
	192.168.100.0/24 indicates to a router / computer that you have a
network addressed as 192.168.100.x, and hosts potentially numbered 1
thru 254 (allowing 254 hosts in a /24 network.)

	Since you used a 24 bit netmask ( /24 or 255.255.255.0 ) you were
effectively telling your computer that eth0 and pan0 were in the same
network, and that any traffic bound for that network could be routed to
either. (The actual priority used is rather more involved and depends on
lots of other things.) This means that your computer would be equally
likely (depending on a lot of things) to send traffic to your default
route (and onwards to the internet) via eth0 or pan0, since
192.168.100.1 (possibly your default route) is accessible equally well
from pan0 and eth0 - it's in the same network - and mostly in networking
terms we'd make the assumption that it is also L2 (Layer 2) adjacent -
it plugs into the same Layer 2 switch and can communicate with other
devices in the 192.168.100.0/24 space without having to route. In
technical terms, L2 adjacency means routing is not performed, and a MAC
address is sought (via arp request) - a scenario likely to fail since I
imagine your default route router is not really accessible from pan0.

	I hope this helps - it's rather a simple concept once you know the
background to how ethernet and TCP/IP works, but there's quite a lot of
background there :)

	If I can clarify further, please just ask. I've tried to throw in
enough technical terms that you can use Google to find out more (if
you're interested) but I hope I've explained things well enough that you
at least can understand the basic concept. Do let me know if I've
pitched at the right level or if I'm way off ;)

	Best regards,
	-->Gar