Subinterface Mtu; Vlan Subinterfaces On Ethernet Bundles; Layer 2 Vpn On Vlans - Cisco ASR 9000 Series Configuration Manuallines

The Carrier Ethernet Model
Subinterfaces are distinguished from one another by adding an extension on the end of the interface name
and designation. For instance, the Ethernet subinterface 23 on the physical interface designated TenGigE
0/1/0/0 would be indicated by TenGigE 0/1/0/0.23.
Before a subinterface is allowed 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,
the VLAN identifier must be explicitly defined.

Subinterface MTU

The subinterface Maximum Transmission Unit (MTU) is inherited from the physical interface with an additional
four bytes allowed for the 802.1Q VLAN tag.

VLAN Subinterfaces on Ethernet Bundles

An Ethernet bundle is a group of one or more Ethernet ports that are aggregated together and treated as a
single link. Multiple VLAN subinterfaces can be added to a single Ethernet bundle.
For more information about configuring Ethernet bundles, see the
document. The procedure for creating VLAN subinterfaces on an Ethernet bundle is exactly the same as the
procedure for creating VLAN subinterfaces on a physical Ethernet interface.
To create a VLAN subinterface on an Ethernet bundle, see the
later in this chapter.

Layer 2 VPN on VLANs

The Layer 2 Virtual Private Network (L2VPN) feature enables Service Providers (SPs) to provide L2 services
to geographically disparate customer sites, as described in the
the The Carrier Ethernet Model, on page 5
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 Attachment Circuit, you need to include the l2transport
keyword in the interface command string to specify that the interface is a L2 interface.
VLAN ACs support three modes of L2VPN operation:
• Basic Dot1Q Attachment Circuit—The Attachment Circuit covers all frames that are received and sent
• QinQ Attachment Circuit—The Attachment Circuit covers all frames received and sent with a specific
• Q-in-Any Attachment Circuit—The Attachment Circuit covers all frames received and sent with a specific
with a specific VLAN tag.
outer VLAN tag and a specific inner VLAN tag. QinQ is an extension to Dot1Q that uses a stack of two
tags.
outer VLAN tag and any inner VLAN tag, as long as that inner VLAN tag is not Layer 3 terminated.
Q-in-Any is an extension to QinQ that uses wildcarding to match any second tag.
Note The Q-in-Any mode is a variation of the basic Dot1Q mode. In Q-in-Any mode,
the frames have a basic QinQ encapsulation; however, in Q-in-Any mode the
inner tag is not relevant, except for the fact that a few specific inner VLAN tags
are siphoned for specific services. For example, a tag may be used to provide L3
services for general internet access.
L2VPN and Ethernet Services Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.3.x
Configuring Link Bundles
Configuring 802.1Q VLAN Interfaces
Layer 2 VPN on Ethernet Interfaces
chapter.
Subinterface MTU
chapter in this
section
section of
19