A, MPLS
MPLS (Multiprotocol Label Switching, MPLS) is an IP Backbone. The Layer three routing and switching technology, supports IPv4, IPv6, IPX network protocols, is a tunneling technique.
Two, MPLS forwarding principle
1, MPLS header structure
MPLS header is inserted between the header and the Layer-layer header, the MPLS header length of 4 bytes.
- 20 as the tag bit;
- 3-bit EXP field, typically used in COS;
- 1-bit S field, identifies whether the bottom of the stack;
- 8-bit TTL field
2, MPLS architecture
MPLS architecture with a control plane and forwarding plane configuration.
- Control plane: responsible for generating and maintaining routing information and label information
- Forwarding plane: IP is responsible for packet forwarding and packet forwarding MPLS label
3, forwarding process
1) each router or a route entry corresponding to a forwarding equivalence class labels to generate the tag into the tag forwarding table
2) when the data from the IP packets into MPLS domain to the time domain, the insertion of LER MPLS header for a particular tag the paper label forwarding table generated.
3) LSR equipment, according to the label forwarding of MPLS header label to do a swap
4) When IP packets leave the label packets pop operation (POP), forwarded by IP routing.
Third, the label distribution protocol
1 Introduction
Label Distribution Protocol (LDP) for forwarding equivalence class classification, distribution labels, and the label switched path (LSP) establishment and maintenance operations.
2, LDP neighbor relationship
LDP neighbor establishment is divided into two stages, neighbor discovery phase and the session establishment phase
- Neighbor discovery phase
Hello packets are sent using UDP port 646 protocol to discover neighbors- Session establishment phase
using TCP unicast message, the message parameter negotiation after negotiation successfully sent keepalive packets, keepalive packets received when the two sides to end, LDP neighbors build success
Four, MPLS Basic Configuration
Experimental Topology 
Configuration Step
1) Configure the IP address
2) MPLS domain configuration IGP protocol
3) Configure the MPLS
// Configure-ID LSR
MPLS LSR-ID XXXX
// open interfaces and Global MPLS
MPLS
. 4) arranged the LDP
// open interfaces and globally MPLS
MPLS ldp
Experimental verification
// View LDP interfaces
the DISP MPLS interface 
// View LDP neighbor
disp mpls ldp peer