[c-nsp] Learning L2 switching and spanning tree by doing

[Gert Doering]

Hi,

On Thu, Apr 10, 2008 at 04:09:42AM +0200, Kim Onnel wrote:
> I cant seem to get myself to understand spanning tree, SVIs and all the sort
> by just reading, i dont have access to switches to get my hands to
> configure, any suggestions?

For spanning tree, I can recommend the book "Bridges and Routers" from
Radia Perlman (look on amazon.com for "Radia Perlman").  After that, there
is a good whitepaper on Cisco.com that explains rapid spanning-tree, 
which is the "next-generation" STP.

SVI is what Cisco uses for IP routing on the layer2/layer3 devices,
like a 6500 (and it has not really anything to do with "spanning tree").  

It works like this:

 - the layer 2 part of the box defines a VLAN, e.g. "vlan 100", and
   bridges it across layer 2 ports

 - the router side of the box connects into the layer 2 box, with a
   "virtual interface" (there is no "real" ethernet).  This virtual
   interface is named "interface Vlan 100" and cisco names this a "SVI".

Example:

switched things ("as in a layer 2 only switch"):

interface gigabit 3/7
  switchport
  switchport mode access
  switchport access vlan 100
interface gigabit 3/8
  switchport
  switchport mode access
  switchport access vlan 100

routed things:

interface vlan 100
  ip address 10.0.100.1 255.255.255.0

- this is a routed layer 3 interface that's connected to the switch
side that talks to gig 3/7 + gig 3/8.

gert
-- 
USENET is *not* the non-clickable part of WWW!
                                                           //www.muc.de/~gert/
Gert Doering - Munich, Germany                             gert at greenie.muc.de
fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de
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