Ethernet LAN Mac address and VLAns

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Subject Author Date
Mac address and VLAns vicky 06-17-08
Posted by vicky on June 26, 2008, 4:00 am
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wrote:
> In article
>
>
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>
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> > wrote:
> > > --
> > > Rich Seifert =A0 =A0 =A0 =A0 =A0 =A0 =A0Networks and Communications C=
onsulting
> > > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 21885 Bear Creek =
Way
> > > (408) 395-5700 =A0 =A0 =A0 =A0 =A0 =A0Los Gatos, CA 95033
> > > (408) 228-0803 FAX
>
> > > Send replies to: usenet at richseifert dot com
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> > -----------------------------------------------------------------------=
----=AD---
> > -----------------------------------------------------------
>
> > Hello Mr. Rich Seifert
>
> > I want to discuss some of my queries with u as some are not totally
> > asked by text so these also requires figures.
> > but here its not possible to draw figure
> > So can u give me u'r mail id =A0so that i send the queries in files to
> > U....
>
> Did you consider reading the signature on my posting?
>
> --
> Rich Seifert =A0 =A0 =A0 =A0 =A0 =A0 =A0Networks and Communications Consu=
lting
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 21885 Bear Creek Way
> (408) 395-5700 =A0 =A0 =A0 =A0 =A0 =A0Los Gatos, CA 95033
> (408) 228-0803 FAX
>
> Send replies to: usenet at richseifert dot com
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0*****************************- Hide qu=
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--------------------------------------------------------------------

Hello

Can u plz tell me about the DA (Destination Mac Address) and SA
(Source mac Address)

of a frame which contains multicast data (or multicast member ship
requist or leave requist)

is at this case is DA =3D=3D SA
or SA contain a unique mac address of either router or host.

Please tell me

Thanks in advance


Vikrant

Posted by Rich Seifert on June 26, 2008, 11:47 am
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In article

>
> Can u plz tell me about the DA (Destination Mac Address) and SA
> (Source mac Address)
>
> of a frame which contains multicast data (or multicast member ship
> requist or leave requist)
>
> is at this case is DA == SA
> or SA contain a unique mac address of either router or host.
>

You really should read the relevant standards (IEEE 802.3, IEEE
802.1D/Q) and then ask your questions, rather that looking to this group
to provide a tutorial on every aspect of your design.

That said, a source MAC address is never a multicast; it is always a
unique identifier of the station sending the frame, whether an end
station or router.


--
Rich Seifert Networks and Communications Consulting
21885 Bear Creek Way
(408) 395-5700 Los Gatos, CA 95033
(408) 228-0803 FAX

Send replies to: usenet at richseifert dot com

Posted by Walter Roberson on June 27, 2008, 12:53 am
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>That said, a source MAC address is never a multicast; it is always a
>unique identifier of the station sending the frame, whether an end
>station or router.

It's been several years since I last looked at the relevant
documentation, and memory certainly fades with disuse.
Are there exceptions to the above statement that have to do with
virtual redundancy protocols? I have this idea poking out of corner
of my mind that the active master for VRRP (or perhaps it was
a related protocol) assumes as the source MAC the multicast address
for the redundancy group ?

Posted by on August 21, 2008, 2:13 pm
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On Jun 26, 11:53=A0pm, rober...@hushmail.com (Walter Roberson) wrote:
>
> >That said, a source MAC address is never a multicast; it is always a
> >unique identifier of the station sending the frame, whether an end
> >station or router.

> It's been several years since I last looked at the relevant
> documentation, and memory certainly fades with disuse.
> Are there exceptions to the above statement that have to do with
> virtual redundancy protocols?

FYI, what was going through my mind at the time was
RFC 3768

Section 8.2

When a host sends an ARP request for one of the virtual router IP
addresses, the Master virtual router MUST respond to the ARP
request
with the virtual MAC address for the virtual router. The Master
virtual router MUST NOT respond with its physical MAC address.
This
allows the client to always use the same MAC address regardless of
the current Master router.

Section 8.3

If Proxy ARP is to be used on a VRRP router, then the VRRP router
must advertise the Virtual Router MAC address in the Proxy ARP
message. Doing otherwise could cause hosts to learn the real MAC
address of the VRRP router.

7.3. Virtual Router MAC Address

The virtual router MAC address associated with a virtual router is
an
IEEE 802 MAC Address in the following format:

00-00-5E-00-01- (in hex in internet standard bit-order)

This is *not* in the multicast MAC range.

Section 9.2 talks about use with Token Ring and indicates that MACs
from
03-00-00-00-00-80 to 03-00-02-00-00-00 are used for this. The low
order bit is set in this
but because the next higher bit is set as well, this is Token Ring,
not a broadcast or
multicast address.

But then,

5.2.2. Destination Address

The IP multicast address as assigned by the IANA for VRRP is:

224.0.0.18

This is a link local scope multicast address. Routers MUST NOT
forward a datagram with this destination address regardless of its
TTL.


So... we are into some fine distinctions in this discussion. In the
case I was thinking of,
VRRP, source -MAC- addresses will not be multicast, but the -IP-
addresses are
in the multicast range. But the VRRP does twist the second half of
Rich's sentence, that

>> it is always a
> >unique identifier of the station sending the frame, whether an end
> >station or router.

as VRRP uses a constant identifier (per instance) regardless of which
system
is master at the moment: it is "unique" in the sense that *only* the
VRRP master
is allowed to sendout such frames, but it is -not- "unique" in the
sense that the
same MAC could be from any of the configured VRRP servers, dependent
on which one is
in control at the time.

Posted by vicky on June 27, 2008, 1:01 am
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wrote:
> In article
>
>
> > Can u plz tell me about the DA (Destination Mac Address) =A0 and =A0 SA
> > (Source mac Address)
>
> > of a frame which contains multicast data (or multicast member ship
> > requist or leave requist)
>
> > is at this case =A0is =A0DA =3D=3D SA
> > or SA contain a unique mac address of either router or host.
>
> You really should read the relevant standards (IEEE 802.3, IEEE
> 802.1D/Q) and then ask your questions, rather that looking to this group
> to provide a tutorial on every aspect of your design.
>
> That said, a source MAC address is never a multicast; it is always a
> unique identifier of the station sending the frame, whether an end
> station or router.
>
> --
> Rich Seifert =A0 =A0 =A0 =A0 =A0 =A0 =A0Networks and Communications Consu=
lting
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 21885 Bear Creek Way
> (408) 395-5700 =A0 =A0 =A0 =A0 =A0 =A0Los Gatos, CA 95033
> (408) 228-0803 FAX
>
> Send replies to: usenet at richseifert dot com

----------------------------------------------------------------------

Hi,

please go to that link below to see my query stored in a file which
is
accessable as my query need some graphics along with it


http://vikrantpandey.diinoweb.com/files/


and please answer me


Thanks in advance


Vikrant



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