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Thomas Mangin edited this page Mar 6, 2026 · 1 revision

VPLS (Virtual Private LAN Service) Overview

VPLS (Virtual Private LAN Service) is a BGP-based Layer 2 VPN technology that provides multipoint-to-multipoint Ethernet connectivity over IP/MPLS networks. Defined in RFC 4761 (BGP-based autodiscovery) and RFC 4762 (LDP signaling), VPLS enables service providers to deliver transparent LAN services across WAN infrastructure.

ExaBGP provides BGP-based VPLS support per RFC 4761, allowing applications to programmatically announce and receive VPLS routes for automated L2VPN provisioning, service provider networks, and Layer 2 data center interconnect.

Table of Contents

What is VPLS?

VPLS (Virtual Private LAN Service) is a Layer 2 VPN service that emulates a LAN across a WAN. It creates a virtual bridge that connects multiple sites, making them appear as if they're on the same local Ethernet segment, regardless of physical distance.

How VPLS Works

[VPLS Architecture]

Customer Site A                                    Customer Site B
    LAN: 10.1.0.0/24                                  LAN: 10.1.0.0/24
    VLAN: 100                                         VLAN: 100
         │                                                 │
         │                                                 │
      ┌──▼──┐                                          ┌──▼──┐
      │ CE  │                                          │ CE  │
      └──┬──┘                                          └──┬──┘
         │                                                 │
      ┌──▼──────┐       MPLS Core Network          ┌──────▼──┐
      │ PE1     │◄──────────────────────────────────│     PE2 │
      │ VPLS-A  │       BGP Autodiscovery          │  VPLS-A │
      │         │      Pseudowire Mesh              │         │
      └─────────┘                                   └─────────┘
           │                                              │
           │              ┌──────────┐                    │
           └──────────────┤   PE3    │────────────────────┘
                          │  VPLS-A  │
                          └────┬─────┘
                               │
                            ┌──▼──┐
                            │ CE  │
                            └─────┘
                    Customer Site C
                    LAN: 10.1.0.0/24
                    VLAN: 100

Process:

  1. VPLS Instance Creation: PE routers create VPLS instance (virtual bridge)
  2. BGP Autodiscovery: PEs announce VPLS membership via BGP (RFC 4761)
  3. Pseudowire Setup: Full mesh or hub-and-spoke pseudowires established (using LDP or BGP signaling)
  4. Label Block Allocation: Each PE advertises MPLS label block for incoming traffic
  5. MAC Learning: PEs learn MAC addresses from local CEs and remote PEs
  6. Forwarding: Ethernet frames encapsulated in MPLS and forwarded through pseudowires

Key Components:

  • PE (Provider Edge): Router connected to customer, maintains VPLS instance
  • CE (Customer Edge): Customer Ethernet switch/router, unaware of MPLS
  • VPLS Instance: Virtual bridge (broadcast domain) on PE
  • Pseudowire: Point-to-point tunnel between two PEs for a VPLS instance
  • MP-BGP: Autodiscovery mechanism for VPLS membership (RFC 4761)
  • Label Block: Range of MPLS labels for demultiplexing pseudowires

Why Use VPLS?

Advantages Over Traditional L2 Technologies

Feature VPLS Traditional L2 (VPWS, L2TP) EVPN
Topology Multipoint-to-multipoint Point-to-point Multipoint-to-multipoint
Scalability Moderate (hundreds of sites) Limited (manual config) High (thousands of sites)
MAC Learning Data plane flooding N/A Control plane (BGP)
Autodiscovery Yes (BGP-based) No Yes (BGP-based)
Provisioning Automated (BGP) Manual Automated (BGP)
Multi-homing Basic No Advanced (active-active)
Protocol RFC 4761/4762 RFC 4447, L2TP RFC 7432

Common Use Cases

  1. Enterprise WAN: Connect multiple branch offices as single LAN
  2. Data Center Interconnect: Layer 2 stretch between data centers
  3. Service Provider L2VPN: Carrier Ethernet services (E-LAN)
  4. Legacy Application Support: Applications requiring Layer 2 adjacency
  5. Disaster Recovery: Active-standby sites with Layer 2 replication

ExaBGP VPLS Capabilities

ExaBGP provides RFC 4761 BGP-based VPLS autodiscovery implementation:

Supported Features

✅ VPLS NLRI (Network Layer Reachability Information):

  • Route Distinguisher (RD) for uniqueness
  • VPLS Endpoint ID (VE-ID)
  • Label Block (base, offset, size)
  • BGP-based VPLS autodiscovery

✅ Route Target Extended Communities:

  • Import RT: Controls VPLS instance route import
  • Export RT: Attached to VPLS routes
  • Layer 2 Info extended community (encapsulation, MTU)

✅ Label Block Signaling:

  • Base label (starting label in block)
  • Block offset (position within block)
  • Block size (number of labels)
  • Automatic label allocation signaling

✅ Standard BGP Attributes:

  • AS-PATH, MED, LOCAL_PREF, COMMUNITIES
  • All standard attributes apply to VPLS routes

Implementation:

  • src/exabgp/bgp/message/update/nlri/vpls.py (VPLS NLRI encoding/decoding)
  • src/exabgp/configuration/l2vpn/vpls.py (VPLS configuration parsing)

RFC Support

  • RFC 4761: Virtual Private LAN Service (VPLS) Using BGP for Auto-Discovery and Signaling - Fully Implemented
  • RFC 4762: Virtual Private LAN Service (VPLS) Using LDP Signaling (BGP autodiscovery portion)
  • RFC 4360: BGP Extended Communities Attribute - Fully Implemented
  • RFC 4664: Framework for Layer 2 Virtual Private Networks (L2VPNs) - Context

VPLS vs EVPN

VPLS is the predecessor to EVPN. While both provide Layer 2 VPN services, EVPN offers significant improvements.

Feature VPLS (RFC 4761/4762) EVPN (RFC 7432)
MAC Learning Data plane (flooding) Control plane (BGP)
BUM Traffic Flooding required Optimized (Route Type 3)
Multi-homing Active-standby Active-active (ESI)
Scalability Moderate (flooding limits) High (BGP MAC learning)
ARP Suppression No Yes (built-in)
Integrated L3 No (separate protocol) Yes (Route Type 5)
Use Case Focus Service provider L2VPN Data center fabrics, VXLAN
Maturity Legacy (2007) Modern (2015+)

Migration Path: Many deployments are migrating from VPLS to EVPN for improved scalability and features. ExaBGP supports both for transitional architectures.

When to Use VPLS:

  • Legacy networks with existing VPLS infrastructure
  • Service provider Carrier Ethernet services (where EVPN not yet deployed)
  • Interoperability with older PE routers lacking EVPN support

When to Use EVPN:

  • New deployments (greenfield)
  • Data center fabrics with VXLAN
  • High-scale environments (10,000+ MACs)
  • Multi-homing requirements

Key Concepts

Route Distinguisher (RD)

The Route Distinguisher makes each VPLS instance unique in the BGP routing table, allowing multiple customers to use overlapping Ethernet addresses (same MAC addresses in different VPNs).

Format: ASN:Value or IP:Value

Types:

  • Type 0: 65000:100 (2-byte AS : 4-byte value)
  • Type 1: 192.0.2.1:100 (IPv4 address : 2-byte value)
  • Type 2: 4200000000:100 (4-byte AS : 2-byte value)

Purpose: Uniqueness in BGP table (does NOT control import/export - that's RT's job).

Example:

Customer A VPLS: RD 65001:100
Customer B VPLS: RD 65002:100

BGP Table:
  65001:100:VPLS-Route → Customer A
  65002:100:VPLS-Route → Customer B

Route Target (RT)

The Route Target extended community controls which VPLS instances import which routes.

Format: target:ASN:Value

Example:

PE1 VPLS-A:
  Route Distinguisher: 65001:100
  Export RT: target:65001:100
  Import RT: target:65001:100

PE2 VPLS-A:
  Route Distinguisher: 65002:100
  Export RT: target:65001:100  ← Exports with same RT
  Import RT: target:65001:100  ← Imports routes with this RT

Result: PE1 and PE2 establish pseudowire for VPLS-A

VPLS NLRI Components

The VPLS NLRI advertised via BGP contains:

  1. Route Distinguisher (RD): Makes route unique
  2. VE-ID (VPLS Edge Identifier): Endpoint identifier (0-65535)
  3. Label Block:
    • Base Label: Starting MPLS label value
    • Offset: Position within label block
    • Size: Number of labels in block

Example VPLS NLRI:

RD: 65001:100
VE-ID: 10
Base Label: 10000
Offset: 0
Size: 10

Result: PE allocates labels 10000-10009 for this VPLS instance

Label Block

The Label Block is a range of MPLS labels advertised by each PE for a VPLS instance. Remote PEs use labels from this block to forward traffic to the advertising PE.

How Label Blocks Work:

PE1 advertises:
  VE-ID: 10
  Base: 10000, Offset: 0, Size: 10
  → Labels 10000-10009 available

PE2 advertises:
  VE-ID: 20
  Base: 20000, Offset: 0, Size: 10
  → Labels 20000-20009 available

PE3 advertises:
  VE-ID: 30
  Base: 30000, Offset: 0, Size: 10
  → Labels 30000-30009 available

Pseudowire Establishment:
  PE1 → PE2: PE1 uses label 20000 (PE2's base label)
  PE1 → PE3: PE1 uses label 30000 (PE3's base label)
  PE2 → PE1: PE2 uses label 10000 (PE1's base label)
  PE2 → PE3: PE2 uses label 30000 (PE3's base label)
  PE3 → PE1: PE3 uses label 10000 (PE1's base label)
  PE3 → PE2: PE3 uses label 20000 (PE2's base label)

Label Selection Formula:

Label = Base + (Remote_VE_ID - Offset) % Size

Note: The label block mechanism allows efficient full-mesh pseudowire setup without per-peer signaling.

Configuration Examples

Basic VPLS Configuration

# /etc/exabgp/vpls.conf

neighbor 192.0.2.1 {
    router-id 192.0.2.2;
    local-address 192.0.2.2;
    local-as 65001;
    peer-as 65000;

    # Enable L2VPN VPLS address family
    family {
        l2vpn vpls;
    }

    # API process for dynamic VPLS announcements
    api {
        processes [ vpls-controller ];
    }
}

process vpls-controller {
    run python3 /etc/exabgp/vpls-announce.py;
    encoder text;
}

Static VPLS Route Configuration

# /etc/exabgp/vpls-static.conf

neighbor 192.0.2.1 {
    router-id 192.0.2.2;
    local-address 192.0.2.2;
    local-as 65001;
    peer-as 65000;

    family {
        l2vpn vpls;
    }

    # Static VPLS route
    l2vpn {
        vpls customer-a {
            endpoint 10;                      # VE-ID
            base 10000;                       # Base label
            offset 0;                         # Block offset
            size 10;                          # Block size (10 labels)
            rd 65001:100;                     # Route Distinguisher
            next-hop 192.0.2.2;              # Next-hop (this PE)

            # Route Target for import/export
            extended-community [ target:65001:100 ];

            # Optional: Layer 2 Info
            # l2info:<encapsulation>:<control>:<MTU>:<reserved>
            extended-community [ l2info:19:0:1500:0 ];
        }
    }
}

Encapsulation Types (l2info):

  • 19: Ethernet (most common)
  • 10: Frame Relay
  • 11: ATM

API Examples

Announce VPLS Route (Text API)

Basic VPLS announcement:

#!/usr/bin/env python3
# /etc/exabgp/vpls-announce.py

import sys
import time

def announce_vpls(ve_id, base, offset, size, rd, rt, nexthop="self"):
    """Announce VPLS route"""
    print(f"announce vpls "
          f"route-distinguisher {rd} "
          f"endpoint {ve_id} "
          f"base {base} "
          f"offset {offset} "
          f"size {size} "
          f"next-hop {nexthop} "
          f"extended-community [ target:{rt} l2info:19:0:1500:0 ]")
    sys.stdout.flush()

def withdraw_vpls(ve_id, base, offset, size, rd, rt, nexthop="self"):
    """Withdraw VPLS route"""
    print(f"withdraw vpls "
          f"route-distinguisher {rd} "
          f"endpoint {ve_id} "
          f"base {base} "
          f"offset {offset} "
          f"size {size} "
          f"next-hop {nexthop} "
          f"extended-community [ target:{rt} l2info:19:0:1500:0 ]")
    sys.stdout.flush()

# Announce VPLS instance
announce_vpls(
    ve_id=10,           # This PE's VE-ID
    base=10000,         # Base label
    offset=0,           # Label block offset
    size=10,            # 10 labels (10000-10009)
    rd="65001:100",     # Route Distinguisher
    rt="65001:100"      # Route Target
)

# Keep process running
while True:
    time.sleep(60)

Text API Format Examples

Announce VPLS route:

print("announce vpls "
      "route-distinguisher 65001:100 "
      "endpoint 10 "
      "base 10000 "
      "offset 0 "
      "size 10 "
      "next-hop self "
      "extended-community [ target:65001:100 l2info:19:0:1500:0 ]")
sys.stdout.flush()

Withdraw VPLS route:

print("withdraw vpls "
      "route-distinguisher 65001:100 "
      "endpoint 10 "
      "base 10000 "
      "offset 0 "
      "size 10 "
      "next-hop self "
      "extended-community [ target:65001:100 l2info:19:0:1500:0 ]")
sys.stdout.flush()

JSON API Format

Received VPLS route (JSON format from ExaBGP):

{
  "exabgp": "5.0",
  "type": "update",
  "neighbor": {
    "address": {"local": "192.0.2.2", "peer": "192.0.2.1"},
    "message": {
      "update": {
        "announce": {
          "l2vpn vpls": {
            "65001:100": {
              "endpoint": 20,
              "base": 20000,
              "offset": 0,
              "size": 10,
              "attributes": {
                "next-hop": "192.0.2.1",
                "extended-community": [
                  "target:65001:100",
                  "l2info:19:0:1500:0"
                ]
              }
            }
          }
        }
      }
    }
  }
}

Use Cases

1. Enterprise WAN (Multi-Site LAN Extension)

Scenario: Enterprise with 50 branch offices requiring transparent LAN connectivity (same broadcast domain).

How VPLS Helps:

  • All sites appear on same Ethernet segment
  • Any-to-any connectivity without complex VPN mesh
  • Transparent to end devices (plug-and-play)
  • Support for non-IP protocols (NetBIOS, IPX, etc.)

ExaBGP Role:

  • Automate VPLS instance provisioning
  • Announce VPLS routes for each PE
  • Integrate with orchestration for dynamic branch addition
  • Programmatic VE-ID and label block management

Example Topology:

Branch 1 ──┐
Branch 2 ──┤
Branch 3 ──┼─── [MPLS Core + ExaBGP VPLS] ─── All branches in single
Branch 4 ──┤                                   Layer 2 broadcast domain
Branch 5 ──┘

2. Data Center Interconnect (L2 Stretch)

Scenario: Two data centers requiring Layer 2 connectivity for VM mobility and shared VLANs.

How VPLS Helps:

  • Stretch VLANs across data centers
  • VM migration without IP address changes
  • Shared storage traffic (iSCSI, NFS)
  • Disaster recovery with Layer 2 replication

ExaBGP Role:

  • Announce VPLS routes for DCI links
  • Health-check-based route withdrawal (failover)
  • Integration with data center orchestration
  • Dynamic VPLS instance creation per tenant

3. Service Provider Carrier Ethernet (E-LAN)

Scenario: Service provider offering Ethernet multipoint services to enterprise customers.

How VPLS Helps:

  • Deliver multipoint Ethernet service (E-LAN)
  • Each customer gets isolated VPLS instance
  • SLA enforcement (bandwidth, latency)
  • Scalable service provisioning

ExaBGP Role:

  • Automate customer VPLS provisioning via API
  • Integrate with OSS/BSS systems
  • Programmatic VE-ID allocation
  • Policy-based RT assignment

4. Legacy Application Support

Scenario: Applications requiring Layer 2 adjacency (NetBIOS, legacy clustering, proprietary protocols).

How VPLS Helps:

  • Maintain Layer 2 adjacency over Layer 3 WAN
  • Support non-IP protocols
  • Broadcast/multicast support
  • Transparent to legacy applications

ExaBGP Role:

  • Dynamic VPLS provisioning for legacy apps
  • Integration with application lifecycle management
  • Automated setup/teardown of VPLS instances

5. Financial Services (Low-Latency Trading)

Scenario: Trading applications requiring low-latency Layer 2 connectivity between trading engines and exchanges.

How VPLS Helps:

  • Direct Layer 2 connectivity (minimal latency)
  • Multicast support for market data
  • Deterministic forwarding
  • No routing overhead

ExaBGP Role:

  • Rapid VPLS failover (withdraw routes on link failure)
  • Integration with market data feeds
  • Monitoring and alerting via API

Common Errors and Solutions

Error: "VPLS endpoint missing"

Cause: VE-ID (endpoint) not specified in VPLS announcement.

Solution: Always specify endpoint parameter.

# Incorrect
print("announce vpls route-distinguisher 65001:100 base 10000 offset 0 size 10")

# Correct
print("announce vpls "
      "route-distinguisher 65001:100 "
      "endpoint 10 "  # Required
      "base 10000 offset 0 size 10 "
      "next-hop self")

Error: "VPLS base label missing"

Cause: Base label not specified.

Solution: Include base, offset, and size parameters.

print("announce vpls "
      "route-distinguisher 65001:100 "
      "endpoint 10 "
      "base 10000 "     # Required
      "offset 0 "       # Required
      "size 10 "        # Required
      "next-hop self")

Error: "VPLS size inconsistency"

Cause: Base label + size exceeds maximum MPLS label value (2^20 - 1 = 1048575).

Solution: Use valid label ranges. Maximum label is 1048575.

# Invalid: 1048570 + 10 = 1048580 > 1048575
base 1048570
size 10

# Valid
base 10000
size 100

Error: "Route Distinguisher required"

Cause: VPLS routes must include a Route Distinguisher.

Solution: Always specify route-distinguisher.

print("announce vpls "
      "route-distinguisher 65001:100 "  # Required
      "endpoint 10 base 10000 offset 0 size 10 "
      "next-hop self")

Error: "Route Target extended community missing"

Cause: Without Route Target, VPLS routes won't be imported into VPLS instances.

Solution: Include at least one Route Target.

print("announce vpls "
      "route-distinguisher 65001:100 "
      "endpoint 10 base 10000 offset 0 size 10 "
      "next-hop self "
      "extended-community [ target:65001:100 ]")  # Required

Error: "VPLS routes announced but no pseudowires established"

Cause: ExaBGP announces VPLS routes via BGP but does NOT establish pseudowires. The PE router must create pseudowires.

Solution: ExaBGP provides autodiscovery (BGP signaling). The PE router must:

  • Have VPLS instance configured with matching RD/RT
  • Establish pseudowires using signaled label blocks
  • Configure LDP or BGP signaling for pseudowire setup

Remember: ExaBGP announces VPLS membership via BGP but does NOT create pseudowires or forward Ethernet frames.

Error: "L2VPN family not enabled on peer"

Cause: Remote router doesn't have L2VPN VPLS address family configured.

Solution: Enable L2VPN VPLS on both ExaBGP and the peer router.

Cisco IOS-XR:

router bgp 65000
 neighbor 192.0.2.2
  address-family l2vpn vpls-vpws  ← Enable L2VPN
  !
 !
!

Juniper Junos:

protocols {
    bgp {
        group exabgp {
            family l2vpn {  ← Enable L2VPN
                signaling;
            }
        }
    }
}

Important Considerations

ExaBGP Does Not Manipulate RIB/FIB

⚠️ CRITICAL: ExaBGP is a BGP protocol engine. It does NOT:

  • Create VPLS instances on routers
  • Establish pseudowires between PEs
  • Create Ethernet bridges
  • Forward Layer 2 frames
  • Install VPLS routes in FIB

What ExaBGP DOES:

  • ✅ Send/receive VPLS routes via BGP (RFC 4761 autodiscovery)
  • ✅ Encode VPLS NLRIs with RD, VE-ID, label blocks
  • ✅ Provide API for applications to control VPLS routes
  • ✅ Handle BGP session management

External Infrastructure Required:

  • PE Routers: Cisco, Juniper, Nokia, Arista routers with VPLS support
  • MPLS Network: LDP or RSVP-TE for transport labels
  • VPLS Instance Configuration: VPLS instances must be pre-configured on PE routers
  • Pseudowire Signaling: LDP or BGP signaling for pseudowire establishment

Typical Architecture:

[Your Application]
       │
       ├─→ [ExaBGP] ─── BGP VPLS ───→ [PE Routers]
       │      (Autodiscovery)             │
       │                                  ├─ VPLS Instance Creation
       │                                  ├─ Pseudowire Setup (LDP/BGP)
       │                                  └─ Ethernet Bridging
       │
       └─→ [Orchestration] ───NETCONF───→ [PE Routers]
              (VPLS Provisioning)

Label Block Management

Important: The label block values in ExaBGP announcements signal to remote PEs which labels to use. The PE router must:

  • Allocate labels from its label space
  • Map labels to VPLS instance and pseudowires
  • Program MPLS forwarding for incoming labeled traffic

Best Practice:

  • Use consistent VE-ID allocation scheme (unique per PE)
  • Coordinate label blocks to avoid conflicts
  • Reserve label ranges per VPLS instance

VPLS Scalability Limitations

Data Plane Flooding:

  • VPLS uses data plane MAC learning (flood-and-learn)
  • Broadcast, Unknown unicast, Multicast (BUM) traffic flooded to all PEs
  • High BUM traffic can cause scaling issues

Full Mesh Pseudowires:

  • Each PE requires pseudowire to every other PE in VPLS instance
  • N PEs = N*(N-1)/2 pseudowires
  • Large deployments (100+ PEs) can be challenging

MAC Table Size:

  • PEs must learn MACs from all sites
  • Hardware limits on MAC table size

Migration to EVPN: For large-scale deployments (1000+ MACs, 50+ sites), consider migrating to EVPN which addresses these limitations with control-plane MAC learning and optimized BUM handling.

Performance Considerations

  • Pseudowire Scale: Typically 100-1000 pseudowires per PE (hardware-dependent)
  • MAC Scale: 10,000-100,000 MACs per VPLS instance (hardware-dependent)
  • BGP Convergence: VPLS autodiscovery convergence typically 1-5 seconds
  • Data Plane: Line-rate MPLS forwarding (hardware-dependent)

Best Practices:

  • Use Route Reflectors for large deployments (avoid full mesh BGP)
  • Implement split horizon to prevent loops
  • Configure MAC aging timers appropriately
  • Monitor pseudowire status and BUM traffic levels

Security Considerations

  • BGP Authentication: Use MD5 or TCP-AO for BGP sessions
  • Route Filtering: Import/Export policies on PE routers
  • Label Spoofing: Ensure labels are not leaked between VPLS instances
  • Access Control: Restrict who can inject VPLS routes via ExaBGP API

See Also

ExaBGP Documentation

Use Cases

Operations

Getting Started

References

RFCs and Standards

ExaBGP Resources

Vendor Documentation

  • Cisco VPLS Configuration: VPLS configuration guides for IOS, IOS-XE, IOS-XR
  • Juniper VPLS: Junos VPLS routing instances and BGP autodiscovery
  • Nokia SR OS: VPLS service configuration

Books and Articles

  • MPLS and VPN Architectures (Ivan Pepelnjak, Jim Guichard) - Comprehensive L2VPN/VPLS guide
  • Deploying IP and MPLS QoS for Multiservice Networks (John Evans, Clarence Filsfils) - VPLS QoS considerations

VPLS vs EVPN Migration

  • RFC 7432: BGP MPLS-Based Ethernet VPN (EVPN) - Modern alternative to VPLS
  • EVPN Migration Guides: Strategies for migrating VPLS to EVPN

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