MPLS

MPLS

notion image
Router generates local labels for each network in the routing table, and advertises to adjacent routers.
MPLS labels are locally significant to the router
  • A label is created for each IP destination
  • Neighbors use the labels learned from their neighbors
  • Labels of direclty connected neighbors need to be known
LDP - Label distribution protocol
LSP - Label switch path
LSR - Label switch router
Labels added to packets at layer 2.5
Routers swap the label, don’t need to look at layer 3 information.
IPv6 can go over IPv4 network.
Labels are 32 bits
  • 20 Bits Label
  • 3 bit Experimental (QoS)
  • 1 bit bottom of stack (set to 1, top/transit label set to 0)
  • 8 bits TTL
Labels 0-15 are reserved
imp-null (3) Directly connected
PHP - Penultimate hop popping - remove label before it hits the final router. (Default)
mpls ip

int gi1/0 
	mpls ip
Constrain range of lables
mpls label range 100 199
show mpls ldp bindings 5.5.5.5 32
show mpls forwarding-table 5.5.5.5
notion image
notion image
 
🏷️
Label distribution protocol (LDP)

Transport Address

Router ID, by default is the transport address
  1. Configured
  1. Highest IP on loopback
  1. Highest IP on Interface
int g2/0
	mpls ldp discovery transport-address interface

VRF Utilities

ping vrf 101:ACME 172.16.101.2
traceroute vrf 101:ACME 172.16.101.2

traceroute mpls ipv4 5.5.5.5 255.255.255.255

show ip route vrf 101:ACME
ip route vrf 101:ACME 10.10.10.0 255.255.255.0 172.16.101.2
MPLS Layer 2 VPNs
MPLS Layer 2 VPNs
MPLS Layer 3 VPNs
MPLS Layer 3 VPNs