The core layer is a high-speed switching backbone and should be designed to
switch packets as fast as possible. This layer of the network should not
perform any packet manipulation, such as access lists and filtering, that
would slow down the switching of packets.
The distribution layer of the network is the demarcation point between the
access and core layers and helps to define and differentiate the core. The
purpose of this layer is to provide boundary definition and is the place at
which packet manipulation can take place.
The access layer is the point at which local end users are allowed into the
network. This layer may also use access lists or filters to further optimise
the needs of a particular set of users.
Judging by your diagram, your core and access switches are one and the same,
such that you do not have separate, dedicated backbone switches providing
high-speed interconnections between distribution and access layer devices.
I expect that these definitions slip somewhat when you move into smaller
networks as this design concept is really geared towards the large campus
network rather than the small and medium sized networks such as is in your
illustration.
--
Edward Solomon
CCNA, CCSI
Senior I/T Specialist
Networking Solutions
IBM Canada Ltd. - Learning Services
Tel.: (905) 316-3241 Fax: (905) 316-3101
E-mail: [EMAIL PROTECTED]
Internet: http://www.can.ibm.com/services/learning/net_internet.html
"Ole Drews Jensen" <[EMAIL PROTECTED]> wrote in message
2019FB428FD3D311893700508B71EBFB134AAC@RWR_MAIL_SVR">news:2019FB428FD3D311893700508B71EBFB134AAC@RWR_MAIL_SVR...
> (this e-mail is best viewed with a fixed font like Courier)
>
>
> I can't seem to picture the theory behind Cisco's 'Three Layer Model' with
> Core, Distribution and Access layers.
>
> Below, I have designed a minor network where the headquarter's LAN is made
> up of three switches (1,2 and 3) and they are connecting to four branch
> offices via a WAN connection from router 1 and 2. Router 1 connects the
> first three branch offices via Frame Relay, and Router 2 connects the last
> office via DSL.
>
> Can someone kindly match the right layers (core, dist. or access) with the
> right switches and routers?
>
> Also, if someone has a very good way of explaining this, I would
appreciate
> it.
>
>
> =======================
> R-n = Router Number n
> S-n = Switch Number n
> -----------------------
> PRN = Printer
> SVR = Server
> W = Workstation
> =======================
>
> 1GB BACKBONE
> ---------------------------
> | | |
> [S-1] [S-2] [S-3]
> W-------||||| SVR--||||| SVR-|||||
> W--------|||| SVR---|||| SVR--||||
> W---------||| W------||| PRN---|||
> W----------|| W-------|| PRN----||
> W-----------| | |
> | |
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~[R-1]~~~~~~~~[R-2]~~~~~~~
> | |
> | |
> FRAME RELAY DSL
> | | | |
> [S-4] | | | | [S-7]
> |||||--[R-3]-----------| | | [R-6]------|||||--W
> W--|||| | | ||||---W
>
> W---||| | | |||----W
> W----|| [R-4] | ||-----W
> W-----| |-------| | |------W
> [S-5] [R-5]
> | |
> W |
> [S-6]
> | |
> W W
>
>
>
> Thanks in advance,
>
> Ole
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~
> Ole Drews Jensen
> Systems Network Manager
> CCNA, MCSE, MCP+I
> RWR Enterprises, Inc.
> [EMAIL PROTECTED]
> ~~~~~~~~~~~~~~~~~~~~~~~~~
>
> ___________________________________
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