Specifications

Configuring Routing Between VLANs
How to Configure Routing Between VLANS
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Configuring Routing Between VLANs with IEEE 802.1Q Encapsulation
This section describes the required and optional tasks for configuring routing between VLANs with
IEEE 802.1Q encapsulation. The IEEE 802.1Q protocol is used to interconnect multiple switches and
routers, and for defining VLAN topologies.
Prerequisites
Configuring routing between VLANs with IEEE 802.1Q encapsulation assumes the presence of a single
spanning tree and of an explicit tagging scheme with one-level tagging.
You can configure routing between any number of VLANs in your network.
Restrictions
The IEEE 802.1Q standard is extremely restrictive to untagged frames. The standard provides only a
per-port VLANs solution for untagged frames. For example, assigning untagged frames to VLANs takes
into consideration only the port from which they have been received. Each port has a parameter called a
permanent virtual identification (Native VLAN) that specifies the VLAN assigned to receive untagged
frames.
The main characteristics of the IEEE 802.1Q are that it assigns frames to VLANs by filtering and that
the standard assumes the presence of a single spanning tree and of an explicit tagging scheme with
one-level tagging.
This section contains the configuration tasks for each protocol supported with IEEE 802.1Q
encapsulation. The basic process is the same, regardless of the protocol being routed. It involves the
following tasks:
• Enabling the protocol on the router
• Enabling the protocol on the interface
• Defining the encapsulation format as IEEE 802.1Q
• Customizing the protocol according to the requirements for your environment
To configure IEEE 802.1Q on your network, perform the following tasks. One of the following tasks is
required depending on the protocol being used.
• Configuring AppleTalk Routing over IEEE 802.1Q (required)
• Configuring IP Routing over IEEE 802.1Q (required)
• Configuring IPX Routing over IEEE 802.1Q (required)
The following tasks are optional. Perform the following tasks to connect a network of hosts over a simple
bridging-access device to a remote access concentrator bridge between IEEE 802.1Q VLANs. The
following sections contain configuration tasks for the Integrated Routing and Bridging, Transparent
Bridging, and PVST+ Between VLANs with IEEE 802.1Q Encapsulation:
• Configuring a VLAN for a Bridge Group with Default VLAN1 (optional)
• Configuring a VLAN for a Bridge Group as a Native VLAN (optional)