802.1Q Vlan; 802.1Q Tagged Frames; Subinterfaces - Cisco ASR 9000 Series Configuration Manuallines

802.1Q VLAN

• L2 Switched Service (Bridging)—The EFP is mapped to a bridge domain, where frames are switched
• L2 Stitched Service (AC to AC xconnect)—This covers point-to-point L2 associations that are statically
• Tunneled Service (xconnect)—The EFP is mapped to a Layer 3 tunnel. This covers point-to-point services
• L2 Terminated Service (Ethernet access to Layer 3 service)—The EFP is mapped to an IP interface that
802.1Q VLAN
A VLAN is a group of devices on one or more LANs that are configured so that they can communicate as if
they were attached to the same wire, when in fact they are located on a number of different LAN segments.
Because VLANs are based on logical instead of physical connections, it is very flexible for user and host
management, bandwidth allocation, and resource optimization.
The IEEE's 802.1Q protocol standard addresses the problem of breaking 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 Gigabit Ethernet and10-Gigabit Ethernet
interfaces.

802.1Q Tagged Frames

The IEEE 802.1Q tag-based VLAN uses an extra tag in the MAC header to identify the VLAN membership
of a frame across bridges. This tag is used for VLAN and Quality of Service (QoS) priority identification.
The VLANs can be created statically by manual entry or dynamically through Generic Attribute Registration
Protocol (GARP) VLAN Registration Protocol (GVRP). The VLAN ID associates a frame with a specific
VLAN and provides the information that switches must process the frame across the network. A tagged frame
is four bytes longer than an untagged frame and contains two bytes of Tag Protocol Identifier (TPID) residing
within the type and length field of the Ethernet frame and two bytes of Tag Control Information (TCI) which
starts after the source address field of the Ethernet frame.

Subinterfaces

Subinterfaces are logical interfaces created on a hardware interface. These software-defined interfaces allow
for segregation of traffic into separate logical channels on a single hardware interface as well as allowing for
better utilization of the available bandwidth on the physical interface.
L2VPN and Ethernet Services Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.3.x
18
based on their destination MAC address. This includes multipoint services:
• Ethernet to Ethernet Bridging
• Multipoint Layer 2 Services
established and do not require a MAC address lookup.
• Ethernet to Ethernet Local Switching—The EFP is mapped to an S-VLAN either on the same port
or on another port. The S-VLANs can be identical or different.
only:
• EoMPLS
• L2TPv3
has a global address or belongs to a VRF (includes both IP and MPLS Layer 3 VPNs).
The Carrier Ethernet Model