6
Tasks at a glance
(Optional.)
660H
Setting MPLS MTU
(Optional.)
661H
Specifying the label type advertised by egress
(Optional.)
662H
Configuring TTL propagation
(Optional.)
663H
Enabling sending MPLS TTL-expired messages
(Optional.)
664H
Enabling MPLS forwarding statistics
(Optional.)
665H
Enabling split horizon for MPLS forwarding
(Optional.)
666H
Enabling SNMP notifications for MPLS
16B
Enabling MPLS
Before you enable MPLS, perform 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. As a best practice, 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
4.
Enable MPLS on the
interface.
mpls enable
By default, MPLS is disabled on
the interface.
17B
Setting MPLS MTU
MPLS adds the label stack between the link layer header and network layer header of each packet.
To make sure the size of MPLS labeled packets is smaller than the MTU of an interface, configure an
MPLS MTU on the interface.
MPLS compares each MPLS packet against the interface MPLS MTU. When the packet exceeds the
MPLS MTU:
•
If fragmentation is allowed, MPLS performs the following operations:
a.
Removes the label stack from the packet.
b.
Fragments the IP packet. The length of a fragment is the MPLS MTU minus the length of the
label stack.
c.
Adds the label stack to each fragment, and forwards the fragments.
•
If fragmentation is not allowed, the LSR drops the packet.