The specific steps and complexity of setting up an L3 VPN may vary based on your unique requirements, the technology chosen, and whether you use a service provider. It's often beneficial to work with experienced network professionals or consult with your chosen service provider for guidance and support. Typically, the steps involved are:
Planning: Determine your network requirements, including the number of sites, IP address schemes, and routing protocols to use.
Select a provider: Choose a service provider or decide if you will manage the VPN in-house.
Choose VPN type: Decide between MPLS-based VPNs (typically provided by carriers) or IPsec-based VPNs (for site-to-site or remote access).
Design IP addressing: Plan IP address assignments for each site and ensure they don't overlap.
Configure routers: Set up customer edge (CE) routers at each site. Configure routing protocols (e.g. BGP) for communication.
Provider edge (PE) routers: Configure PE routers at provider network edges, enabling MPLS (for MPLS VPNs) or IPsec (for IPsec VPNs).
VRF instances: Create Virtual Routing and Forwarding (VRF) instances on PE routers for each VPN, ensuring traffic isolation.
Route distinguishers (RD) and Route targets (RT): Assign unique RDs and RTs to VRF instances to control route distribution.
BGP configuration: Set up BGP sessions between CE and PE routers, applying import and export policies to control routing.
Label distribution: For MPLS VPNs, ensure MPLS label distribution between PE routers to establish label-switched paths (LSPs).
Quality of Service (QoS): Optionally, configure QoS policies for traffic prioritisation or management.
Security measures: Implement security measures, such as access control lists (ACLs), to protect VPN traffic.
Testing and verification: Thoroughly test the VPN configuration, verifying connectivity and functionality.
Monitoring and maintenance: Continuously monitor the VPN's performance, addressing any issues and making necessary adjustments.
