From: Michael Snyder (msnyder@xxxxxxx)
Date: Thu Aug 22 2002 - 11:07:41 GMT-3
The point of having four ports is to get four times the traffic. If
they all have the same mac, then you get one traffic flow at all four
ports.
This is a design flaw.
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Colin Barber
Sent: Thursday, August 22, 2002 8:31 AM
To: ccielab@groupstudy.com
Subject: RE: Challenge Question
Sun quad Ethernet cards seems to use the same mac address for all four
ports
by default. Looking at the cam entries on the switch it does indeed
create
multiple cam entries. Therefore both machines would get each others
traffic
as well as their own.
This would affect performance on the devices but they would still work.
Normally the Ethernet cards look for packets addressed to it's own mac
address, others are discarded. However as the mac address matches the
traffic would have to be passed up to layer 3 only for the TCP/IP stack
to
reject the packet as it has no record for the flow. This operation would
be
done by generating an interrupt on the main CPU which is why performance
would be affected.
Colin
-----Original Message-----
From: Brian [mailto:signal@shreve.net]
Sent: 22 August 2002 14:03
To: msnyder@revolutioncomputer.com
Cc: ccielab@groupstudy.com
Subject: RE: Challenge Question
On Thu, 22 Aug 2002, Michael Snyder wrote:
> The two ip address with one mac address isn't a problem. You can go
> into the ip advanced settings on a w2k box, and setup as many
addresses
> as you like. As long as the machine responds to the arp ip lookup, it
> works.
>
> Two of the same mac addresses on the same subnet would be a bad thing.
> Might work if you are using a hub instead of a switch, but both
machines
> would get each others traffic.
Are you 100% convinced that a switch would not install 2 CAM entries and
just send data to both? As far as both machines receiving eachothers
traffic, do you believe this would create a problem where the function
is
lost, or just slow performance.........think about how that traffic
would
be handled.
Brian
> > -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
Of
> Brian
> Sent: Thursday, August 22, 2002 6:34 AM
> To: ccielab@groupstudy.com
> Subject: Challenge Question
>
> I know this group likes these challenge questions, so I have one for
you
>
> and hopefully it has not been put to this group recently.
>
> You have two hosts each with identical MAC addresses on an ethernet
LAN.
> They also have identical IP addresses. Why or why not would this be a
> problem for the client communicating (assuming each of the dupe
machines
>
> doesnt need to communicate with eachother only to other hosts on the
LAN
> and through the gateway)?
>
> Ok, similar to above, same MAC addresses but different IP addresses.
> Why
> or why not would this create communications on the LAN or through the
> gateway?
>
> good luck!
>
> Brian
>
>
>
> -----------------------------------------------
> Brian Feeny, CCIE #8036 e: signal@shreve.net
> Network Engineer p: 318.222.2638x109
> ShreveNet Inc. f: 318.221.6612
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