Chapter 5: Configuration & Implementation

Learn practical MPLS configuration and implementation techniques, from basic MPLS setup to advanced L3VPN deployments, with real-world configuration examples and verification commands.

Basic MPLS Configuration

Setting up MPLS requires enabling MPLS forwarding on interfaces and configuring an IGP for LSP establishment. Here's the fundamental configuration steps:

MPLS Enablement Steps

1. Enable MPLS globally → 2. Configure IGP → 3. Enable MPLS on interfaces → 4. Configure LDP

Core Router Configuration

! Enable MPLS globally
ip cef
mpls ip

! Configure OSPF
router ospf 1
 router-id 1.1.1.1
 network 0.0.0.0 255.255.255.255 area 0

! Interface configuration
interface GigabitEthernet0/0
 ip address 10.1.1.1 255.255.255.252
 mpls ip
 no shutdown

PE Router Configuration

! Enable MPLS globally
ip cef
mpls ip

! Configure loopback
interface Loopback0
 ip address 2.2.2.2 255.255.255.255

! Core-facing interface
interface GigabitEthernet0/0
 ip address 10.1.1.2 255.255.255.252
 mpls ip
 no shutdown

LDP Configuration

LDP configuration involves setting up neighbor relationships, configuring router IDs, and establishing targeted LDP sessions for advanced services.

Configuration Task	Command	Purpose	Default
Enable LDP globally	mpls ldp router-id loopback0	Set LDP router ID	Highest IP address
Enable LDP on interface	mpls ip	Enable label distribution	Disabled
Configure targeted LDP	mpls ldp neighbor x.x.x.x targeted ldp	Establish remote sessions	Not configured
LDP discovery hello	mpls ldp discovery hello interval	Adjust hello timers	5 seconds

Complete LDP Configuration Example

! LDP global configuration
mpls ldp router-id loopback0 force
mpls ldp discovery hello interval 10
mpls ldp discovery hello holdtime 30

! Targeted LDP for PE-PE sessions
mpls ldp neighbor 3.3.3.3 targeted ldp
mpls ldp neighbor 4.4.4.4 targeted ldp

! Interface-specific LDP settings
interface GigabitEthernet0/0
 mpls ip
 mpls ldp igp sync

L3VPN Configuration

L3VPN configuration involves creating VRFs, configuring MP-BGP, and establishing PE-CE relationships. This section covers comprehensive VPN setup.

VRF Configuration

! Create VRF
ip vrf CUSTOMER_A
 rd 65001:100
 route-target export 65001:100
 route-target import 65001:100

! Assign interface to VRF
interface GigabitEthernet0/1
 ip vrf forwarding CUSTOMER_A
 ip address 192.168.1.1 255.255.255.0
 no shutdown

MP-BGP Configuration

! MP-BGP configuration
router bgp 65001
 bgp router-id 2.2.2.2
 no bgp default ipv4-unicast
 
 neighbor 3.3.3.3 remote-as 65001
 neighbor 3.3.3.3 update-source loopback0
 
 address-family vpnv4
  neighbor 3.3.3.3 activate
  neighbor 3.3.3.3 send-community extended

Static PE-CE

! Static routing
ip route vrf CUSTOMER_A 10.10.10.0 255.255.255.0 192.168.1.2

! Redistribute in BGP
router bgp 65001
 address-family ipv4 vrf CUSTOMER_A
  redistribute static

BGP PE-CE

! BGP PE-CE
router bgp 65001
 address-family ipv4 vrf CUSTOMER_A
  neighbor 192.168.1.2 remote-as 65002
  neighbor 192.168.1.2 activate
  neighbor 192.168.1.2 as-override

OSPF PE-CE

! OSPF PE-CE
router ospf 2 vrf CUSTOMER_A
 router-id 2.2.2.2
 area 0
 network 192.168.1.0 0.0.0.255 area 0
 redistribute bgp 65001 metric 100

Verification Commands

Proper verification is crucial for MPLS network operation. This section covers essential show commands and troubleshooting techniques.

Command	Purpose	Key Information	Troubleshooting Focus
show mpls interfaces	MPLS-enabled interfaces	Interface status, IP, tunnel	Interface MPLS enablement
show mpls ldp neighbors	LDP adjacencies	Neighbor state, addresses	LDP session establishment
show mpls forwarding-table	Label forwarding table	Local/remote labels, next-hops	Label distribution issues
show ip route vrf	VRF routing table	Routes, next-hops, sources	VPN route propagation
show bgp vpnv4 unicast all	VPNv4 BGP table	RD, RT, labels	BGP VPN route exchange

Core MPLS Verification

! Check MPLS interfaces
show mpls interfaces
show mpls interfaces detail

! Verify LDP neighbors
show mpls ldp neighbors
show mpls ldp discovery

! Check label distribution
show mpls forwarding-table
show mpls ldp bindings

VPN Verification

! Check VRF configuration
show ip vrf
show ip vrf detail

! Verify VPN routes
show ip route vrf CUSTOMER_A
show bgp vpnv4 unicast all

! Test connectivity
ping vrf CUSTOMER_A 10.10.10.1
traceroute vrf CUSTOMER_A 10.10.10.1

Troubleshooting Workflow

1. Check physical layer → 2. Verify IGP → 3. Confirm LDP sessions → 4. Validate label distribution → 5. Test VPN connectivity

Next Steps

Now that you understand MPLS configuration, continue to Chapter 6: Advanced Features to learn about traffic engineering, QoS, and other advanced MPLS capabilities.