[CLUE-Tech] Cisco 678 Configuration

[Randy Arabie]

On Thu, Dec 04, 2003 at 10:27:35AM -0500, black at galaxy.silvren.com wrote:
> 
> > But, I could not ping my LAN host from the 678's management interface.
> >
> > The LAN host I am referring to was a laptop hooked directly
> > to the 678 via a cross-over cable.
> >
> > What are multicast MAC addresses?  And who/what/why use(s) them?
> 
> Multicast is used so that multiple recipients can receive a single
> message, and it doesn't have to be sent to them individually one at a
> time (unicast). It's a lot like a broadcast, except not every host on the
> network is obliged to look at the frame, only the hosts wanting to receive
> multicasts on that particular MAC address.
> 
> Multicasts at layer 2 start with "01:00:5E"
> 
> http://www.hep.ucl.ac.uk/~ytl/multi-cast/addresstranslation_01.html has
> some info on this, I googled it real fast. I'm sure there are better
> sources, but this has general info.
> 
> The most typical use of multicast on a LAN I see is routing protocols like
> EIGRP, OSPF, etc. Some applications use them as well. Anything that is
> sourced from a single location and is being sent to multiple recipients on
> the same LAN segment (like streaming video from the CEO going to your
> desktop for example) is a good candidate for it.
> 
> Why you'd be seeing those as belonging to your 678, I don't know.

Perhaps is has something to do with the Cisco's NAT
functionality?

The bad ARP entries were always related to events where a
LAN host tried to connect to a WAN address.
-- 

Allons Rouler!

Randy
http://www.arabie.org/