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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
1.
Enter system view.
2.
Configure an LSR ID for the
local node.
3.
Enter the view of the interface
that needs to perform MPLS
forwarding.
4.
Enable MPLS on the interface.
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.
To set an MPLS MTU for an interface:
Step
1.
Enter system view.
2.
Enter interface view.
3.
Set an MPLS MTU for the
interface.
The following applies when an interface handles MPLS packets:
Command
system-view
mpls lsr-id lsr-id
interface interface-type
interface-number
mpls enable
Command
system-view
interface interface-type
interface-number
mpls mtu value
6
Remarks
N/A
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.
N/A
By default, MPLS is disabled on the
interface.
Remarks
N/A
N/A
By default, no MPLS MTU is set
on an interface.
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