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VC types
Before encapsulating Layer 2 packets with VC labels, PEs process the Layer 2 packets of different link
layer protocols in different manners. A VC type identifies the mode in which a PE processes the Layer 2
packet on the VC. VC types and AC (PE-CE link) types are closely related. An Ethernet link can work with
the following VC types:
•
Ethernet
—P-Tag is not transferred on a PW. For a packet from a CE, if the packet contains a P-tag,
the PE removes the P-tag before encapsulating the packet. If the packet contains no P-tag, the PE
encapsulates the packet directly. For a packet to be sent from a PE to a CE, if the user access mode
is VLAN, the PE adds a P-tag into the packet and then forwards the packet to the CE. If the user
access mode is Ethernet, the PE does not adds a P-tag but directly forwards the packet to the CE.
Rewriting and removing the existing tags are not allowed.
•
VLAN
—Packets transmitted over a PW must carry a P-Tag.
{
If the peer PE does not require the ingress to rewrite the P-tag:
For a packet from a CE to a PE, if the packet contains a P-tag, the PE keeps the P-Tag unchanged
and then encapsulates the packet. If the packet contains no P-tag, the PE adds a null label (the
label value is 0) into the packet, and then encapsulates the packet.
{
If the peer PE requires the ingress to rewrite the P-tag:
For a packet from a CE to a PE, if the packet contains a P-tag, the PE changes the P-Tag to the
VLAN tag (the tag may be a null tag) expected by the peer PE, and then encapsulates the
packet. If the packet contains no P-tag, the PE adds a VLAN tag expected by the peer PE (the
tag value may be 0) and then encapsulates the packet.
For a packet to be sent from a PE to a CE, if the user access mode is VLAN, the PE rewrites or
retains the original P-tag in the packet and then forwards the packet to the CE. If the user access
mode is Ethernet, the PE removes the P-tag and then forwards the packet to the CE.
MPLS L2VPN configuration task list
To set up a remote VC of MPLS L2VPN between two PEs, complete the following tasks:
•
Configure an IGP on the PEs and P devices to ensure IP connectivity in the backbone.
•
Configure MPLS, GRE, or MPLS TE to set up public tunnels across the backbone network.
•
Configure a tunneling policy on the PEs for the PEs to select the public tunnels that carry the VC.
•
Configure MPLS L2VPN, set up the VC, and bind the AC to the VC.
NOTE:
The MPLS L2VPN is transparent to a user network. You do not need to perform MPLS L2VPN-specific
configurations on CEs.
To configure MPLS L2VPN:
Task Remarks
Required.
Perform this task to enable MPLS L2VPN. You can
configure other MPLS L2VPN configurations only after
you enable MPLS L2VPN.
