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Routing between VLANs

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design your VLANs around the subnet design. For example, if you have engi-
neering, marketing, sales, and support departments, you will typically--not
always, but typically--create a subnet for each department, making sure you
have room for growth. You would then create a VLAN for each department.
In Chapter 3, we discussed the difference between local and end-to-end
VLANs. Regardless of the type of VLAN you configure, each of these types
would associate with a subnet.

Each device within a VLAN would have a default gateway of the inter-

VLAN device connected to its LAN. The inter-VLAN device would then
route any packets with a destination not on the local network.

Before configuring routing between your VLANs, you need to understand

the type of data sharing that is needed. By understanding the user and busi-
ness needs, you can design the network with load balancing and/or redun-
dant links if needed.

There are basically three options that you can choose from:

Multiple links

A single trunked link

Route Switch Module (RSM)

Multiple Links

You can configure your VLANs to communicate by connecting a router
interface into a switch port that is configured for each VLAN. Each work-
station in the VLAN would have its default gateway configured for this
router interface. Figure 6.1 shows how this might look in an internetwork.

F I G U R E 6 . 1

Routers with multiple links

F0/0
F0/1
F0/2

VLAN 1
VLAN 2
VLAN 3

VLAN 1

VLAN 2

VLAN 3

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