HP FlexNetwork 10500 Series Configuration Manual page 335

−
If the packet contains a P-tag, the PE removes the P-tag, and adds a PW label and an
outer tag into the packet before forwarding it.
−
If the packet contains no P-tag, the PE directly adds a PW label and an outer tag into the
packet before forwarding it.
For a packet to a CE:

−
If the access mode is configured as VLAN by using the ac interface command, the PE
adds a P-tag into the packet before sending it to the CE.
−
If the access mode is configured as Ethernet by using the ac interface command, the
PE directly sends the packet to the CE.
You cannot rewrite or remove existing tags.
•
VLAN—Packets transmitted over a PW must carry a P-tag.
For a packet from a CE:

−
If the peer PE does not require the ingress to rewrite the P-tag, the PE keeps the P-tag
unchanged for the packet, 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, the PE changes the P-tag to the
expected VLAN tag (the tag value might be 0), and then adds a PW label and an outer
tag into the packet. If the packet contains no P-tag, the PE adds a VLAN tag expected by
the peer PE (the tag value might be 0), and then adds a PW label and an outer tag into
the packet.
For a packet to a CE:

−
If the access mode is configured as VLAN by using the ac interface command, the PE
rewrites or retains the P-tag before forwarding the packet.
−
If the access mode is configured as Ethernet by using the ac interface command, the
PE removes the P-tag before forwarding the packet.
Ethernet over MPLS supports the following modes:
•
Port mode—A Layer 3 Ethernet interface is bound to a PW. Packets received from the Layer 3
Ethernet interface are forwarded through the bound PW. The default PW type for port mode is
Ethernet.
Figure 85 Packet encapsulation in port mode
packet
CE 1
•
VLAN mode—A Layer 3 Ethernet subinterface is bound to a PW. Packets received from the
VLAN are forwarded through the bound PW. The peer PE can modify the VLAN tag as needed.
The default PW type for VLAN mode is VLAN.
•
Flexible mode—An Ethernet service instance on a Layer 2 Ethernet interface or Layer 2
aggregate interface is bound to a PW. Packets that are received from the interface and meet the
match criteria of the Ethernet service instance are forwarded through the bound PW. You can
Tunnel label
PW label
Control word
(optional)
packet
Tunnel
PE 1
MPLS or IP backbone
326
packet
PE 2 CE 2