In previous parts, we built a complete EVPN-VXLAN fabric:

• Part 1 → Underlay Network

• Part 2 → BGP EVPN Overlay

• Part 3 → VXLAN + Anycast Gateway

Now in Part 4, we focus on:

• Connecting end devices (Test PCs/Servers)
• Configuring ESI Multihoming (Active-Active redundancy)
• Connecting Test PCs (Single-homed)

This is where your design becomes production-ready.

What is ESI Multihoming?

ESI (Ethernet Segment Identifier) allows a server to connect to multiple leaf switches simultaneously.

Without ESI:

• Single-homed → No redundancy
• Link failure = Server down

With ESI Multihoming:

• Dual-homed → Connected to 2 leafs
• Active-Active forwarding
• No STP required

Step 1: Configure Server Bond (Test PC)

On Linux server (or VM), configure bonding:

mode=802.3ad (LACP)
bond0 → eth0 + eth1
IP → 192.168.10.10/24
GW → 192.168.10.1

This allows:

• Load balancing
• Redundancy
• Seamless failover

Step 2: Configure ESI on Leaf01

set interfaces ae0 aggregated-ether-options lacp active
set interfaces ae0 aggregated-ether-options esi 00:11:22:33:44:55:66:77:88:99
set interfaces ae0 unit 0 family ethernet-switching interface-mode access
set interfaces ae0 unit 0 family ethernet-switching vlan members C1-VLAN10

Step 3: Configure ESI on Leaf02

⚠️ IMPORTANT: Same ESI must be used on both leafs

set interfaces ae0 aggregated-ether-options lacp active
set interfaces ae0 aggregated-ether-options esi 00:11:22:33:44:55:66:77:88:99
set interfaces ae0 unit 0 family ethernet-switching interface-mode access
set interfaces ae0 unit 0 family ethernet-switching vlan members C1-VLAN10

Step 4: Enable All-Active Multihoming

set protocols evpn ethernet-segment all-active

This enables:

• Active-Active forwarding
• Load balancing across both leafs

Step 5: Configure AE Interfaces

Add physical interfaces into AE bundle:

Leaf01

set interfaces xe-0/0/9 ether-options 802.3ad ae0

Leaf02

set interfaces xe-0/0/9 ether-options 802.3ad ae0

Step 1: Access Port Configuration (Leaf01)

set interfaces xe-0/0/10 unit 0 family ethernet-switching interface-mode access
set interfaces xe-0/0/10 unit 0 family ethernet-switching vlan members C1-VLAN10

set interfaces xe-0/0/11 unit 0 family ethernet-switching interface-mode access
set interfaces xe-0/0/11 unit 0 family ethernet-switching vlan members C2-VLAN20

Step 2: Access Port Configuration (Leaf02)

set interfaces xe-0/0/10 unit 0 family ethernet-switching interface-mode access
set interfaces xe-0/0/10 unit 0 family ethernet-switching vlan members C1-VLAN10

set interfaces xe-0/0/11 unit 0 family ethernet-switching interface-mode access
set interfaces xe-0/0/11 unit 0 family ethernet-switching vlan members C2-VLAN20

Test Devices Setup

On Leaf01

• PC1 → VLAN 10
  • IP: 192.168.10.10/24
  • GW: 192.168.10.1
• PC2 → VLAN 20
  • IP: 192.168.20.10/24
  • GW: 192.168.20.1

On Leaf02

• PC3 → VLAN 10
  • IP: 192.168.10.20/24
  • GW: 192.168.10.1
• PC4 → VLAN 20
  • IP: 192.168.20.20/24
  • GW: 192.168.20.1

Expected Connectivity

👉 Same VLAN traffic is extended across fabric using VXLAN.

Traffic Flow Explained

Same VLAN Traffic (Across Leafs)

Example:

• PC1 → PC3 (VLAN 10)

Flow:

• PC1 → Leaf01 → VXLAN Tunnel → Leaf02 → PC3

Learned via EVPN (no flooding)

Dual-Homed Server Traffic

• Load-balanced across Leaf01 & Leaf02
• Both links active

Failure Scenario

• One leaf down → traffic continues
• No session drop

Key Benefits

• Active-Active server connectivity
• No Spanning Tree
• Seamless Layer 2 extension
• Optimal traffic forwarding
• High availability

Common Mistakes

• VLAN mismatch across leafs
• Missing VNI mapping
• Wrong gateway IP
• ESI mismatch
• LACP not configured on server

Full Series Recap

• Part 1 → Underlay Network

• Part 2 → BGP EVPN Overlay

• Part 3 → VXLAN + Anycast Gateway

• Part 4 → Test PCs + ESI Multihoming