Re: [fw-wiz] Layer 2 (stealth) firewalls - PBR?



On Mon, 7 Apr 2008, Darden, Patrick S. wrote:

Except that a layer two device can't tell if something is multicast or
broadcast or unicast or Anything in ipv4 or ipv6.... That's sorta the
definition of a layer two device. If it could discriminate amongst
layer 3 traffic, it would be a layer 3 device--a router, firewall, etc.

I've been doing networking since the broadband/baseband LAN thing a long
time ago, and I'm pretty cognizant of how it all works...

Layer 2 devices like switches have to forwrd layer 3 multicast packets out
ports for the multicast group, so they in essence have to peek up a layer
even though they're not "routers, firewalls, etc." They also have to
forward layer 3 broadcasts out all ports in a LAN or VLAN, once again
without being "routers, firewalls, etc."

Finally, there are alyer 2 broadcasts and layer 2 multicast addresses.
I'd suggest a Google of "layer 2 multicast addresss" for your increased
edification, and a good read of the IPv6 RFCs- because if you don't think
this stuff is going to be where "interesting" attacks and "poor
implementations" happen...

Paul
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