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This chapter describes the required and optional tasks for configuring routing between VLANs with IEEE 802.1Q encapsulation.
Shared port adapters (SPAs) on Cisco ASR 1000 Series Aggregation Services Router have a limit of 8,000 TCAM entries, which limits the number of VLANs you can create on a single SPA.
The IEEE 802.1Q protocol is used to interconnect multiple switches and routers, and for defining VLAN topologies. 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 IEEE 802.1Q are as follows:
Assigns frames to VLANs by filtering.
The standard assumes the presence of a single spanning tree and of an explicit tagging scheme with one-level tagging.
IP routing over IEEE 802.1Q extends IP routing capabilities to include support for routing IP frame types in VLAN configurations using the IEEE 802.1Q encapsulation.
To route IP over IEEE 802.1Q between VLANs, you need to customize the subinterface to create the environment in which it will be used. Perform the tasks described in the following sections in the order in which they appear:
IP routing is automatically enabled in the Cisco IOS XE software for routers. To reenable IP routing if it has been disabled, perform the following steps.
Once you have IP routing enabled on the router, you can customize the characteristics to suit your environment. If necessary, refer to the IP configuration chapters in the Cisco IOS XE IP Routing Protocols Configuration Guide , Release 2, for guidelines on configuring IP.
| Command or Action | Purpose | |
|---|---|---|
|
Step 1 |
enable Example: |
Enables privileged EXEC mode.
|
|
Step 2 |
configure terminal Example: |
Enters global configuration mode. |
|
Step 3 |
ip routing Example: |
Enables IP routing on the router. |
|
Step 4 |
end Example: |
Exits privileged EXEC mode. |
To define the encapsulation format as IEEE 802.1Q, perform the following steps.
| Command or Action | Purpose | |
|---|---|---|
|
Step 1 |
enable Example: |
Enables privileged EXEC mode.
|
|
Step 2 |
configure terminal Example: |
Enters global configuration mode. |
|
Step 3 |
interface gigabitethernet card / spaslot / port . subinterface-number Example: |
Specifies the subinterface on which IEEE 802.1Q will be used, and enters interface configuration mode. |
|
Step 4 |
encapsulation dot1q vlanid Example: |
Defines the encapsulation format as IEEE 802.1Q (dot1q ), and specifies the VLAN identifier |
|
Step 5 |
end Example: |
Exits subinterface configuration mode. |
An interface can have one primary IP address. To assign a primary IP address and a network mask to a network interface, perform the following steps.
| Command or Action | Purpose | |||
|---|---|---|---|---|
|
Step 1 |
enable Example: |
Enables privileged EXEC mode.
|
||
|
Step 2 |
configure terminal Example: |
Enters global configuration mode. |
||
|
Step 3 |
interface gigabitethernet card / spaslot / port . subinterface-number Example: |
Specifies the subinterface on which IEEE 802.1Q will be used, and enters interface configuration mode. |
||
|
Step 4 |
ip address ip-address mask Example: |
Sets a primary IP address for an interface.
|
||
|
Step 5 |
end Example: |
Exits subinterface configuration mode. |
To indicate whether a VLAN is a native VLAN, perform the following steps.
| Command or Action | Purpose | |
|---|---|---|
|
Step 1 |
enable Example: |
Enables privileged EXEC mode.
|
|
Step 2 |
show vlans Example: |
Displays VLAN information. |
|
Step 3 |
end Example: |
Exits privileged EXEC mode. |
This configuration example shows IP being routed on VLAN 101:
!
ip routing
!
interface gigabitethernet 4/1/1.101
encapsulation dot1q 101
ip addr 10.0.0.0 255.0.0.0
!|
Related Topic |
Document Title |
|---|---|
|
IP LAN switching commands: complete command syntax, command mode, defaults, usage guidelines, and examples |
|
Standard |
Title |
|---|---|
|
No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature. |
-- |
|
MIB |
MIBs Link |
|---|---|
|
No new or modified MIBs are supported by this feature, and support for existing MIBs has not been modified by this feature. |
To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL: |
|
RFC |
Title |
|---|---|
|
No new or modified RFCs are supported by this feature, and support for existing standards has not been modified by this feature. |
-- |
|
Description |
Link |
|---|---|
|
The Cisco Support website provides extensive online resources, including documentation and tools for troubleshooting and resolving technical issues with Cisco products and technologies. To receive security and technical information about your products, you can subscribe to various services, such as the Product Alert Tool (accessed from Field Notices), the Cisco Technical Services Newsletter, and Really Simple Syndication (RSS) Feeds. Access to most tools on the Cisco Support website requires a Cisco.com user ID and password. |
The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.|
Feature Name |
Releases |
Feature Information |
|---|---|---|
|
Configuring Routing Between VLANs with IEEE 802.1Q Encapsulation |
Cisco IOS XE Release 2.1 |
This feature was introduced on the Cisco ASR 1000 Series Aggregation Services Routers. |
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