Inter-VLAN Routing THE CCNP EXAM TOPICS COVERED IN THIS

Inter-VLAN Routing
THE CCNP EXAM TOPICS COVERED IN THIS
CHAPTER INCLUDE THE FOLLOWING:


Understand VLAN trunking protocols including 802.1Q, ISL,
and the dynamic trunking protocol.


Describe inter-VLAN routing and name the components.


Configure access ports for static membership of single and
multiple VLANs.


Configure ports as 802.1Q trunks and verify their operation.


Configure ports as ISL trunks and verify their operation.


Identify the Cisco Route Switch processors and explain how
they are implemented.

First, let’s have a quick review. Routers break up broadcast domains,
and layer 2 switches are used to break up collision domains. If you
connect all your switches together, they will be in one broadcast
domain. You can break up broadcast domains in layer 2 switched networks by creating virtual
LANs (VLANs). However, the hosts within a VLAN can communicate only within the same VLAN
by default.
Obviously you cannot bridge together VLANs, because that would allow the forwarding
of broadcasts across the VLAN boundary and would just create a larger single VLAN. For
devices in one VLAN to communicate with devices in a different VLAN, they must be routed
through a layer 3 device. This is called
inter-VLAN routing
. You can perform inter-VLAN
routing with internal route processors in a layer 2 switch or with an external router called an
external route processor
.
In this chapter, we cover both internal route processors and external route processors and
explain how to configure them for inter-VLAN configuration.

The term
route processor
is used commonly when discussing the device used
for inter-VLAN communications, but we should be clear. This is really just a
router, either running externally or as firmware or software in a switch. Modern
implementations of route processors run IOS and support routing protocols in
common with routers.