Re: Mac address and VLAns
- From: vicky <vikrant.pandey@xxxxxxxxx>
- Date: Thu, 19 Jun 2008 21:04:01 -0700 (PDT)
On Jun 17, 8:05 pm, Rich Seifert <use...@xxxxxxxxxxxxxxxxxxxxxxx>
wrote:
In article
<217d310b-921f-40de-97d0-10f41b430...@xxxxxxxxxxxxxxxxxxxxxxxxxxx>,
vicky <vikrant.pan...@xxxxxxxxx> wrote:
Hi,
Plz explain ...
A single mac address is able to be a member of multiple vlans.
A MAC address is not a "member" of a VLAN. It is *frames* (not MAC
addresses, ports, IP addresses, or anything else) that are associated
with particular VLANs. The rules for associating frames with VLANs can
be based on almost any characteristic of the frame, such as:
-the switch port on which the frame arrived (port-based VLAN)
-the MAC source address in the frame (MAC address-based VLAN)
-the IP subnet identifier within the frame (IP subnet-based VLAN)
-the TCP/UDP port number within the frame (application-based VLAN), etc.
While many people may *think* they are associating a port (or a MAC
address) with a VLAN, they are really specifying a VLAN-association rule
that is based on switch port (or MAC address); the distinction is
subtle, but important, particularly when end stations are VLAN-aware,
and perform the association themselves.
Consider a multi-homed VLAN-aware end station (e.g., a server) that
associates frames with VLANs based on IP subnet identifiers. Since that
station has multiple IP addresses (that's what multi-homed means), it
will emit frames carrying different VLAN IDs, depending on the subnet to
which the frame is directed. However, that station may have the same MAC
address on all subnets (sidebar: I never said that the server had
multiple physical interfaces, and even if it did, it is permissible to
assign the same MAC address to multiple interfaces that are not on the
same LAN). Thus, this is a device that, according to *your* model, has a
MAC address that is a "member" of multiple VLANs. This dichotomy
disappears when one realizes that it is the *frames* that are associated
with the VLANs, and each frame is associated with one (and only one)
VLAN.
If you don't like the multi-homed station example, the same phenomenon
arises in the case of a single-homed station that associates VLAN IDs
based on application streams; e.g., a video delivery server (think:
Intranet multicast delivery of training videos) that assigns a VLAN to
each video stream so that bandwidth can be conserved within an
enterprise. Another example is a VoIP conference-call server,
associating each conference call (multicast) to a VLAN.
There is a complete explanation of this in Chapter 11 of "The Switch
Book."
--
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
------------------------------------------------------------------
Sir ...
As u mentioned about a book .... The Switch Book...
can u plz ... give a full detail of this book (publication, writer
etc)
so that it is easy for me to find it at book stores....
Vikrant.
.
- Follow-Ups:
- Re: Mac address and VLAns
- From: jpd
- Re: Mac address and VLAns
- References:
- Mac address and VLAns
- From: vicky
- Re: Mac address and VLAns
- From: Rich Seifert
- Mac address and VLAns
- Prev by Date: FREE SOFTWARE DOWNLOAD
- Next by Date: Re: Mac address and VLAns
- Previous by thread: Re: Mac address and VLAns
- Next by thread: Re: Mac address and VLAns
- Index(es):
Relevant Pages
|
