Establish MPLS Transport Label Distribution via LDP¶

Preparing The Lab¶

Log into the LabAccess jumpserver:
1. Type labs, or select Option 97 to get to the Additional Labs menu.
2. Type or select the option for mesh-topology-ipvpn-labs to access the LDP and IPVPN labs.
3. Type ldp in this menu to configure the topology with the necessary prerequisites.

Lab Tasks¶

With IS-IS in place as the IGP for Loopback reachability, enable LDP for MPLS Label Distribution on EOS1.
1. First, we must enable MPLS forwarding on the router.
```
mpls ip
```
2. Enable the Label Distribution Protocol for MPLS.
```
mpls ldp
    no shutdown
```
3. Set Loopback0 as the interface for transport and Router-ID functions.
```
mpls ldp
    router-id interface Loopback0
    transport-address interface Loopback0
```
4. Disable LDP globally on the router interfaces then selectively enable on Service Provider facing interfaces and the Loopback0 interface for transport.
  
  Note
  
  By default when LDP is enabled, EOS will attempt peering on all interfaces.
```
interface Ethernet1
    mpls ldp interface
!
interface Ethernet2
    mpls ldp interface
!
interface Ethernet4
    mpls ldp interface
!
interface Ethernet5
    mpls ldp interface
!
interface Loopback0
    mpls ldp interface
!
mpls ldp
    interface disabled default
```
5. Enable LDP Hello Redundancy to help maintain adjacencies in link-flap scenarios to cut down on session reestablishment time.
  
  Note
  
  Devices with Hello Redundancy enabled will begin sending Targeted Hello messages to the Transport Address found in the received LDP Link Hello message. The Targeted Hello adjacency can support the session established between peers even when all Link Hello adjacencies have timed out. The FEC label bindings between two peers with no Link Hello adjacency will not be active because the Interior Gateway Protocol will not use the other peer as the next hop. Nevertheless, maintaining the FEC label bindings and the session between the two peers can save significant time when the Link Hello adjacency is reestablished.
```
mpls ldp
    neighbor hello-redundancy
```
6. Enable Grace Restart capabilities for LDP to maintain forwarding when agent restarts occur.
  
  Info
  
  LDP Graceful Restart allows the device to preserve its entire MPLS LDP label if the LDP agent restarts and can also preserve the LFIB entries of the peer whose LDP agent has restarted.
```
mpls ldp
    !
    graceful-restart role speaker
        timer state-holding 500
        timer reconnect 500
```
7. Lastly, enable LDP synchronization with IS-IS to ensure MPLS LSPs are generated on valid underlay links.
  
  Note
  
  Sync timers can be adjusted in LDP as desired.
```
router isis 100
    mpls ldp sync default
```
Verify local LDP configuration and MPLS label allocation on EOS1.
1. Display the configured Node SID and other ISIS-SR information.
```
show mpls ldp bindings detail
```
2. Verify the MPLS label range assigned for use with LDP.
  
  Note
  
  EOS has a default allocation range for each type of MPLS label, which you can view. Of interest here is the ldp (dynamic) label range. LDP label bindings are locally significant to the router whose LFIB they exist in.
```
show mpls label ranges
```
Repeat the above configuration steps on the other Service Provider nodes (EOS2 - EOS8) while only activating LDP on the necessary interfaces for each device.

Testing¶

Now that the LDP topology is deployed, verify MPLS label advertisement and reachability. These steps can be performed on any of the Service Provider EOS nodes.

Verify that all router adjacencies are successfully established. You should see an entry for each connected router.
```
show mpls ldp neighbor
show mpls ldp discovery detail
```
Now display the tunnel information LDP will use to inform the data-plane which MPLS labels and interfaces to use to reach the other routers in the topology.

Note

An MPLS label value of the 3 represents the implicit-null label, which signifies the destination or endpoint router is adjacent to this node.
```
show mpls ldp tunnel
```
Verify the Label Bindings dynamically allocated to local and remote interfaces attached to LDP enabled peers.

Info

As mentioned, these labels are dynamically allocated by EOS out of the ldp (dynamic) label range. Also note these label values are only locally significant to the router, so they may overlap between the various nodes in the topology.
```
show mpls ldp bindings detail
```
Test MPLS LSP reachability between routers by using MPLS ping and traceroute functions. This example is from EOS1 to EOS8.
```
ping mpls ldp ip 8.8.8.8/32 source 1.1.1.1
traceroute mpls ldp ip 8.8.8.8/32 source 1.1.1.1
```

Success

Lab Complete!