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Cisco CCNP / BCMSN Exam Tutorial: Static VLANs |
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BCMSN exam success and earning your CCNP certification requires
you to add to your knowledge of VLAN configuration. When you
studied for your CCNA exam, you learned how to place ports
into a VLAN and what the purpose of VLANs was, but you may
not be aware that there are two types of VLAN membership.
To pass the BCMSN exam, you must know the details of both
types.
In this tutorial, we'll take a look at the VLAN type you
are most familiar with, the "static VLAN". As you
know, VLANs are a great way to create smaller broadcast domains
in your network. Host devices connected to a port belonging
to one VLAN will receive broadcasts and multicasts only if
they were originated by another host in that same VLAN. The
drawback is that without the help of a Layer 3 switch or a
router, inter-VLAN communication cannot occur.
The actual configuration of a static VLAN is simple enough.
In this example, by placing switch ports 0/1 and 0/2 into
VLAN 12, the only broadcasts and multicasts hosts connected
to those ports will receive are the ones transmitted by ports
in VLAN 12.
SW1(config)#int fast 0/1
SW1(config-if)#switchport mode access
SW1(config-if)#switchport access vlan 12
% Access VLAN does not exist. Creating vlan 12
SW1(config-if)#int fast 0/2
SW1(config-if)#switchport mode access
SW1(config-if)#switchport access vlan 12
One of the many things I love about Cisco switches and routers
is that if you have forgotten to do something, the Cisco device
is generally going to remind you or in this case actually
do it for you. I placed port 0/1 into a VLAN that did not
yet exist, so the switch created it for me!
There are two commands needed to place a port into a VLAN.
By default, these ports are running in dynamic desirable trunking
mode, meaning that the port is actively attempting to form
a trunk with a remote switch in order to send traffic between
the two switches. The problem is that a trunk port belongs
to all VLANs by default, and we want to put this port into
a single VLAN only. To do so, we run the switchport mode access
command to make the port an access port, and access ports
belong to one and only one VLAN. After doing that, we placed
the port into VLAN 12 with the switchport access vlan 12 command.
Running the switchport mode access command effectively turns
trunking off on that port.
The hosts are unaware of VLANs; they simply assume the VLAN
membership of the port they're connected to. But that's not
quite the case with dynamic VLANs, which we'll examine in
the next part of this BCMSN tutorial.
About the Author:
Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage,
home of free CCNA and CCNP tutorials, The Ultimate CCNA Study
Package, and Ultimate CCNP Study Packages.
For a FREE copy of his latest e-books, “How To Pass
The CCNA” and “How To Pass The CCNP”, visit
the website and download your free copies. You can also get
FREE CCNA and CCNP exam questions every day! Pass the CCNA
exam with The Bryant Advantage!
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