[OT] Traffic from ff:ff:ff:ff:ff:ff in switched environment

[Jason Opperisano]

On Tue, 2004-11-16 at 16:45, Eduardo Fernández wrote:
> Hi all,
> 
> i know this is not strictly about netfilter, but here it goes:

it sure isn't.

> While I was deploying my firewall script, I noticed some weird traffic
> from mac ff:ff:ff:ff:ff:ff in my router's private interface. 

it's more likely that ff:ff:ff:ff:ff:ff is the destination mac, not the
source...

> Later on I
> noticed the same traffic in other computers within the network. The
> traffic was arp who-has packets at a constant rate of about 35 kbytes/s.
> It's a /16 network in a switched environment.

arp "who-has" packets are vital to the proper functioning of a local
area network--it's how each host finds the MAC address associated with
each IP on the network.

the volume of traffic you're seeing is a symptom of the fact that you
have a /16 configured as a flat, switched network.

the guy that i learned TCP/IP networking from once told me a good
guideline is to never have more than 1024 hosts in a single layer-2
broadcast domain, as the broadcast traffic becomes unmanageable.  he
knew a whole lot more than i ever will--so i try to stick to that when i
(re)design a network.

-j

--
"Silly customer, you cannot hurt a Twinkie!"
	--The Simpsons