Panasonic NN46240-710 - Manual (Page 153)

Nortel Secure Router 8000 Series
Troubleshooting - VPN___________ 4 MPLS L2VPN troubleshooting
[Nortel] mpls switch-l2vc 1.1.1.1 2345 between 2.2.2.2 1234 encapsulation
ip-interworking
[Nortel] mpls switch-l2vc 1.1.140.3 2345 between 1.1.140.2 1234 encapsulation hdlc
A combination of VC ID and VC type identifies a VC uniquely in PWE3. When the VC ID is
the same, but the VC type differs, two VCs are determined.
Q: What are the conditions for a PW being up?
A: In a SVC, if a PW is to be Up the conditions are: the local AC is Up and the tunnel is Up. You
can use the display mpls static-l2vc interface command to check the PW status.
In LDP, the conditions for a PW status of Up are:
• The local AC is Up.
• The tunnel is Up.
• The LDP session is Up.
• The MTUs, VC types, and control words are consistent on both ends.
You can use the display mpls l2vc interface command to check the PW status.
Q: What are the differences between tag or untagged configuration in the
Ethernet interface view and tagged or raw configuration in the PWE3 view?
A: The tag or untagged mode of an Ethernet interface has no direct relation with the tagged or
raw mode of a PWE3 tunnel.
• The tag or untagged mode of an Ethernet interface identifies a VLAN and a subinterface
that receives packets sent from AC. By default, Ethernet packets are untagged and VLAN
packets are tagged.
• The tagged or raw mode of PWE3 sets the PWE3 payload to carry a VLAN tag. A PWE3
packet coming out of a tunnel finds its egress based on the tagged or raw configuration.
The fact that the PWE3 packet carries the VLAN tag does not imply that the Ethernet interface
bound with the PWE3 tunnel is configured with the VLAN tag.
Specifying the PWE3 with the Raw mode, you can realize the switching function of the VLAN
tag. For example, the local AC interface is the Ethernet main interface while the remote is the
Ethernet subinterface:
• The packet is received on the Ethernet main interface and the packet is untagged. The
VLAN tag is not added to the packet because the mode of PWE3 is Raw. When the PWE3
tunnel sends the packet to the remote end, the VLAN tag is added to the packet because the
egress is an Ethernet subinterface.
• After the remote Ethernet subinterface receives the packet with the VLAN tag, according
to the Raw mode, the interface removes the VLAN tag and sends out the packet from the
Ethernet main interface.
If both ends of a PW are a VLAN subinterface in tag mode, they must use the same VLAN tag.
Otherwise, the packet is discarded.
In Q-in-Q mode, packets entering a tunnel carry multiple layers of tags. If the mode of PW is
Raw, the outer tag of the packet is removed before the packet is forwarded to the remote tunnel
end.
Issue 5.3 (30 March 2009) Nortel Networks Inc. 4-43