Cisco 10000 - Manual (Page 388)

18-20
Cisco 10000 Series Router Software Configuration Guide
OL-2226-23
Chapter 18 Configuring L2 Virtual Private Networks
Configuration Tasks for L2VPN
• Port mode—Allows a frame coming into an interface to be packed into an MPLS packet and
transported over the MPLS backbone to an egress interface. The entire Ethernet frame is transported
without the preamble or FCS as a single packet.
• VLAN ID Rewrite—Enables you to use VLAN interfaces with different VLAN IDs at both ends of
the tunnel.
You can configure Ethernet over MPLS in the following ways:
• Configuring Ethernet over MPLS in VLAN Mode, page 18-20
• Configuring Ethernet over MPLS in Port Mode, page 18-21
• Configuring Ethernet over MPLS with VLAN ID Rewrite, page 18-27
Ethernet over MPLS Restrictions
The following restrictions pertain to the Ethernet over MPLS transport:
• Packet format: Ethernet over MPLS supports VLAN packets that conform to the IEEE 802.1Q
standard. The 802.1Q specification establishes a standard method for inserting VLAN membership
information into Ethernet frames. The Inter-Switch Link (ISL) protocol is not supported between
the PE and customer edge (CE) routers.
• When the first Ethernet over MPLS in VLAN mode circuit is configured, the controller (the entire
port) is automatically placed in promiscuous mode. The promiscuous mode is removed only when
the last Ethernet over MPLS in VLAN mode circuit associated with that controller is removed.
• The AToM control word is supported. However, if the peer PE router does not support a control
word, the control word is disabled. This negotiation is done by LDP label binding.
• Ethernet packets with hardware-level cyclic redundancy check (CRC) errors, framing errors, and
runt packets are discarded on input.
Configuring Ethernet over MPLS in VLAN Mode
A virtual LAN (VLAN) is a switched network that is logically segmented by functions, project teams,
or applications regardless of the physical location of users. Ethernet over MPLS allows you to connect
two VLAN networks that are in different locations. You configure the PE routers at each end of the
MPLS backbone and add a point-to-point virtual circuit (VC). Only the two PE routers at the ingress and
egress points of the MPLS backbone know about the VCs dedicated to transporting Layer 2 VLAN
traffic. All other routers do not have table entries for those VCs.
For Ethernet over MPLS in VLAN mode, it is possible for VPN circuits to coexist with pseudowire
circuits. Because the port is in promiscuous mode, the frames are filtered by the VLAN ID.
Note You must configure Ethernet over MPLS in VLAN mode on the subinterfaces. However, you cannot
configure Ethernet over MPLS (VLAN mode) on a Q-in-Q subinterface.