Layer 2 (L2) LISP

Layer 2 LISP (Locator/ID Separation Protocol) is an extension of the LISP protocol designed for overlay network virtualization at Layer 2. While traditional LISP primarily operates at Layer 3, Layer 2 LISP focuses on enabling extension of Layer 2 domains across different locations, providing benefits such as mobility, scalability, and simplified network configuration.

Components

Overlay Networks

  • Layer 2 LISP creates an overlay network that allows Layer 2 segments (such as VLANs) to extend across disparate Layer 3 networks.
  • This is useful in scenarios like data center interconnect (DCI) or workload mobility across sites.

MAC Address Mobility

  • Supports seamless mobility of MAC addresses between sites.
  • Devices can retain their MAC addresses and VLAN IDs even when moved across geographic locations.

Locator/Identifier Separation

  • Separates the endpoint identifiers (MAC addresses) from their locations (IP addresses of devices handling the traffic, like routers).
  • Endpoints are identified by their MAC addresses, while traffic is routed based on RLOCs (Routing Locators).

Mapping System

  • Maintains a mapping database that associates endpoint identifiers (MAC addresses) with RLOCs.
  • When a frame is sent, the mapping system determines how to encapsulate and forward the traffic to the correct destination.

Encapsulation

  • Layer 2 traffic is encapsulated using a LISP header for transport across the Layer 3 infrastructure.
  • This encapsulation allows for flexibility in routing and switching Layer 2 frames.

Encapsulation and Decapsulation

  • Ingress Node: The device that receives the Layer 2 frame encapsulates it with a LISP header.
  • Core Network: Encapsulated traffic traverses the Layer 3 core network based on RLOCs.
  • Egress Node: The device that receives the encapsulated frame strips off the LISP header and delivers the original Layer 2 frame to its destination.

Layer 2 LISP enhances network virtualization by extending Layer 2 networks across Layer 3 boundaries while maintaining flexibility, scalability, and ease of management. It is particularly useful in environments requiring high mobility and interconnection of distributed Layer 2 domains.

Use Cases

  • Data Center Interconnect (DCI): Extending VLANs across data centers for workload mobility or disaster recovery.
  • Campus Networks: Simplifying Layer 2 segmentation across different buildings or sites.
  • Branch Connectivity: Extending the same Layer 2 network across branch offices.

Advantages

  • Scalability: Reduces the need for a flat Layer 2 network, which can be challenging to scale.
  • Flexibility: Enables easier segmentation and workload mobility.
  • Reduced Complexity: Simplifies the configuration and management of Layer 2 extensions compared to traditional tunneling methods like VXLAN or GRE.

https://networklessons.com/ip-routing/cisco-locator-id-separation-protocol-lisp