Multi-Protocol Label Switching (MPLS) is a routing technique that assigns short, fixed-length labels to data packets to improve routing speed. MPLS works by mapping IP addresses to labels at the edge of the network. Label Switched Routers inside the network use these labels to make forwarding decisions instead of long IP addresses. The document provides details on MPLS headers, label switched routers, label edge routers, and how to configure and verify MPLS on a sample network topology.

1. Multi-Protocol Label Switching
(MPLS)
Prepared By: Ripan Kumar Ray
Email: riponroy79@gmail.com
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2. Contents
• Introduction
• Characteristics
• How does it work
• MPLS Header
• Label Switched Routers (LSRs) & Label Edge Routers (LERs)
• Configuration
• Verifying MPLS Interfaces

3. Introduction
• Multi-Protocol Label Switching (MPLS) was originally presented as a way of
improving the forwarding speed of routers but is now emerging as a crucial
standard technology that offers new capabilities for large scale IP networks.
• The Internet Engineering Task Force is developing MPLS with draft standards
expected by the end of 1998. MPLS is viewed by some as one of the most
important network developments of the 1990's

4. Characteristics
• Mechanisms to manage traffic flows of various granularities (Flow Management)
• It independent of Layer-2 and Layer-3 protocols.
• Maps IP-addresses to fixed length labels.
• Supports ATM, Frame-Relay and Ethernet

5. HOW DOES IT WORK

6. MPLS Header
The essence of MPLS is the generation of
a short fixed-length label that acts as a
shorthand representation of an IP packet's
header. This is much the same way as a
ZIP code is shorthand for the house, street
and city in a postal address, and the use of
that label to make forwarding decisions
about the packet.

7. Label Switched Routers (LSRs) & Label Edge
Routers (LERs)
In MPLS terminology, the packet handling
nodes or routers are called Label Switched
Routers (LSRs)
At the edge of the network, we require high
performance packet classifiers that can apply
(and remove) the requisite labels: we call
these MPLS edge routers or Label Edge
Routers (LERs)
Finally, as MPLS labelled packets leave the
network, another edge router removes the
labels.

8. Configuration
Fig: Topology

9. Configuration
R1
!
interface Serial2/0
ip address 192.168.12.1 255.255.255.0
no shut
!
interface Serial3/0
ip address 192.168.13.1 255.255.255.0
no shut
!
router ospf 1
network 192.168.12.0 255.255.255.0 area 0
network 192.168.13.0 255.255.255.0 area 0
R2
!
interface Serial2/0
ip address 192.168.12.2 255.255.255.0
no shut
!
interface Serial3/0
ip address 192.168.23.1 255.255.255.0
no shut
!
router ospf 1
network 192.168.12.0 255.255.255.0 area 0
network 192.168.23.0 255.255.255.0 area 0
R3
!
interface Serial2/0
ip address 192.168.13.2 255.255.255.0
no shut
!
interface Serial3/0
ip address 192.168.23.2 255.255.255.0
no shut
!
router ospf 1
network 192.168.13.0 255.255.255.0 area 0
network 192.168.23.0 255.255.255.0 area 0

10. Enabling MPLS
Once you have done this the OSPF adjacencies should be up and running.
Now what we need to do is apply the necessary MPLS command to enable MPLS on network.
R1(config)#int se2/0 R2(config)#int se2/0 R3(config)#int se2/0
R1(config-if)#mpls ip R2(config-if)#mpls ip R3(config-if)#mpls ip
R1(config-if)#int se3/0 R2(config-if)#int se3/0 R3(config-if)#int se3/0
R1(config-if)#mpls ip R2(config-if)#mpls ip R3(config-if)#mpls ip
Once you have applied the single command "mpls ip" on the both sides of the link, an LDP adjacency
will be formed and will display a log shown below:
*Nov 16 04:15:51.811: %SYS-5-CONFIG_I: Configured from console by console
*Nov 16 04:15:52.135: %LDP-5-NBRCHG: LDP Neighbor 192.168.12.1:0 (2) is UP
This means that MPLS is enabled on both sides and the neighbors are exchanging label information.

11. Verifying MPLS Interfaces
R3#sh mpls interfaces
Interface IP Tunnel Operational
Serial1/0 Yes (ldp) No Yes
Serial1/1 Yes (ldp) No Yes

12. Thank You