A VLAN is a group of devices on one or more LANs that you can configure so that the devices can communicate as if they were attached to the same wire. When in fact, they are located on several different LAN segments. Because VLANs are based on logical instead of physical connections, they are flexible for user and host management, bandwidth allocation, and resource optimization.

The IEEE 802.1Q protocol standard addresses the problem of dividing large networks into smaller parts so broadcast and multicast traffic does not consume more bandwidth than necessary. The standard also helps provide a higher level of security between segments of internal networks.

The 802.1Q specification establishes a standard method for inserting VLAN membership information into Ethernet frames.

Cisco IOS XR software supports VLAN subinterface configuration on 40Gigabit, HundredGig, FourHundredGig, and bundle interfaces.

Subinterfaces are logical interfaces that you can create on a hardware interface. These software-defined interfaces allow the segregation of traffic into separate logical channels on a single hardware interface. It also allows for the better utilization of the available bandwidth on the physical interface.

You can distinguish subinterfaces from each other by adding an extension at the end of the interface name and designation. For instance, the system indicates Ethernet subinterface 23 on the physical interface designated TenGigE 0/1/0/0, by TenGigE 0/1/0/0.23.

Before the system allows a subinterface to pass traffic, it must have a valid tagging protocol encapsulation and VLAN identifier assigned. All Ethernet subinterfaces always default to the 802.1Q VLAN encapsulation. However, you must explicitly define the VLAN identifier.

The system inherits the subinterface maximum transmission unit (MTU)from the physical interface with an additional four bytes allowed for the 802.1Q VLAN tag.

The router does not support a native VLAN. However, the equivalent functionality is accomplished using an encapsulation command as follows:

encapsulation dot1q TAG-ID

The Layer 2 Virtual Private Network (L2VPN) feature enables Service Providers (SPs) to provide Layer 2 services to geographically disparate customer sites.

The configuration model for configuring VLAN attachment circuits (ACs) is similar to the model used for configuring basic VLANs, where the user first creates a VLAN subinterface, and then configures that VLAN in subinterface configuration mode. To create an AC, you need to include the l2transport keyword in the interface command string to specify that the interface is a Layer 2 interface.

VLAN ACs support three modes of L2VPN operation:

• Basic Dot1Q AC—The AC covers all frames that are received and sent with a specific VLAN tag.

• QinQ AC— Only outer tag (s-tag) of 0x88a8 and inner tag (c-tag) of 0x8100 is supported.

Keep the following in mind when configuring L2VPN on a VLAN:

• Cisco IOS XR software supports 255 ACs per LC.

Use the show interfaces command to display AC information.

This task explains how to configure 802.1Q VLAN subinterfaces. To remove these subinterfaces, see the “Removing an 802.1Q VLAN Subinterface” section.

Note

You can programmatically configure and retrieve the VLAN interfaces and subinterfaces parameters using openconfig-vlan.yang OpenConfig data model. To get started with using data models, see the Programmability Configuration Guide for Cisco 8000 Series Routers. The OpenConfig VLAN data model uses structured vlan/match containers to represent VLAN matching. The vlan-id leaf supports only a single VLAN value and does not represent VLAN lists or ranges. See the OpenConfig model documentation for details.

RP/0/RP0/CPU0:router# configure

/* Enter subinterface configuration mode and specifies the interface type, location, and subinterface number. */

RP/0/RP0/CPU0:router(config)# interface TenGigE 0/2/0/4.10

• Replace the interface-path-id argument with one of the following instances:

• Physical Ethernet interface instance, or with an Ethernet bundle instance. Naming notation is rack /slot /module /port , and a slash between values is required as part of the notation.

• Ethernet bundle instance. Range is from 1 through 65535.

• Replace the subinterface argument with the subinterface value. Range is from 0 through 4095.

• Naming notation is interface-path-id.subinterface , and a period between arguments is required as part of the notation.

/* Set the Layer 2 encapsulation of an interface. */

RP/0/RP0/CPU0:router(config-subif)# encapsulation dot1q 100

Note	The dot1q vlan command is replaced by the encapsulation dot1q command on the Cisco 8000 Series Router. It is still available for backward-compatibility, but only for Layer 3 interfaces.

/* Assign an IP address and subnet mask to the subinterface. */

RP/0/RP0/CPU0:router(config-subif)# ipv4 address 178.18.169.23/24

• Replace ip-address with the primary IPv4 address for an interface.

• Replace mask with the mask for the associated IP subnet. The network mask can be specified in either of two ways:

• The network mask can be a four-part dotted decimal address. For example, 255.0.0.0 indicates that each bit equal to 1 means that the corresponding address bit belongs to the network address.

• The network mask can be indicated as a slash (/) and number. For example, /8 indicates that the first 8 bits of the mask are ones, and the corresponding bits of the address are network address.

/* The exit command is not explicitly required. */

RP/0/RP0/CPU0:router(config-subif)# exit
RP/0/RP0/CPU0:router(config)# end
or
RP/0/RP0/CPU0:router(config)# commit

• When you issue the end command, the system prompts you to commit changes:

  
  Uncommitted changes found, commit them before exiting(yes/no/cancel)?
  [cancel]:
  

  - Entering yes saves configuration changes to the running configuration file, exits the configuration session, and returns the router to EXEC mode.

  - Entering no exits the configuration session and returns the router to EXEC mode without committing the configuration changes.

  - Entering cancel leaves the router in the current configuration session without exiting or committing the configuration changes.

• Use the commit command to save the configuration changes to the running configuration file and remain within the configuration session.

"RP/0/RP0/CPU0:S3(config)#interface fourHundredGigE 0/5/0/1.100
RP/0/RP0/CPU0:S3(config-subif)#ipv4 address 100.100.100.100/31      
RP/0/RP0/CPU0:S3(config-subif)#encapsulation dot1q 100              
RP/0/RP0/CPU0:S3(config-subif)#no shutdown                          
RP/0/RP0/CPU0:S3(config-subif)#commit 
Mon Jul  8 23:05:01.979 PDT
RP/0/RP0/CPU0:S3(config-subif)#end
RP/0/RP0/CPU0:S3#show interfaces fourHundredGigE 0/5/0/1.100 brief 
Mon Jul  8 23:05:08.784 PDT

               Intf       Intf        LineP              Encap  MTU        BW
               Name       State       State               Type (byte)    (Kbps)
--------------------------------------------------------------------------------
      FH0/5/0/1.100        up        up             802.1Q  1518  400000000

RP/0/RP0/CPU0:S3#show interfaces brief location 0/5/CPU0 | include 802.1Q
Mon Jul  8 23:07:43.929 PDT
      FH0/5/0/1.100        up        up             802.1Q  1518  400000000
RP/0/RP0/CPU0:S3#

RP/0/RP0/CPU0:S3#"

This task explains how to remove 802.1Q VLAN subinterfaces that have been previously configured using the Configuring 802.1Q VLAN subinterfaces section in this module.

RP/0/RP0/CPU0:router# configure

RP/0/RP0/CPU0:router(config)# no interface TenGigE 0/2/0/4.10

Naming notation is instance.subinterface , and a period between arguments is required as part of the notation.

Note	Repeat to remove other VLAN subinterfaces.

RP/0/RP0/CPU0:router(config)# end
or
RP/0/RP0/CPU0:router(config)# commit