H3C Technologies H3C S12500-X Series Switches - Manual (Page 16)

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Sometimes, the egress node must use the TC field in the label to perform QoS. To keep the TC information,
you can configure the egress node to send the penultimate node an explicit null label of 0. If an incoming
packet matches an LFIB entry comprising the explicit null label, the penultimate hop replaces the value of
the top label with value 0, and forwards the packet to the egress node. The egress node gets the TC
information, pops the label of the packet, and forwards the packet.
Protocols and standards
• RFC 3031, Multiprotocol Label Switching Architecture
• RFC 3032, MPLS Label Stack Encoding
• RFC 5462, Multiprotocol Label Switching (MPLS) Label Stack Entry: "EXP" Field Renamed to "Traffic
Class" Field
MPLS configuration task list
Tasks at a glance
(Required.) Enabling MPLS
(Optional.) Configuring MPLS MTU
(Optional.) Specifying the label type advertised by the egress
(Optional.) Configuring TTL propagation
(Optional.) Enabling sending of MPLS TTL-expired messages
(Optional.) Enabling SNMP notifications for MPLS
Enabling MPLS
You must enable MPLS on all interfaces related to MPLS forwarding.
Before you enable MPLS, complete the following tasks:
• Configure link layer protocols to ensure connectivity at the link layer.
• Configure IP addresses for interfaces to ensure IP connectivity between neighboring
nodes.Configure static routes or an IGP protocol to ensure IP connectivity among LSRs.To enable
MPLS:
Step Command Remarks
1. Enter system view. system-view N/A
2. Configure an LSR ID for the local
node.
mpls lsr-id lsr-id
By default, no LSR ID is configured.
An LSR ID must be unique in an MPLS
network and in IP address format.
H3C recommends that you use the IP
address of a loopback interface as
an LSR ID.
3. Enter the view of the interface
that needs to perform MPLS
forwarding.
interface interface-type
interface-number
N/A