arista-evpn-vxlan-clab/docs/HOST_CONFIGURATION.md

Host Interface Configuration Summary

Overview

This document describes the persistent interface configuration approach for hosts in the Arista EVPN-VXLAN lab.

Configuration Method

Hosts use persistent /etc/network/interfaces files mounted via ContainerLab's binds feature. This ensures:

• Configuration persists across container restarts
• Clean deployments without manual post-configuration
• Proper LACP bonding with VLAN tagging on Alpine Linux hosts

Host Configurations

Host1 (VTEP1 - L2 VXLAN on VLAN 40)

• Location: configs/host1-interfaces
• IP Address: 10.40.40.101/24
• VLAN: 40 (tagged)
• Bonding: LACP (802.3ad) using eth1 and eth2
• Connected to: leaf1 (eth1) and leaf2 (eth1)

Host2 (VTEP2 - L3 VXLAN in VRF gold on VLAN 34)

• Location: configs/host2-interfaces
• IP Address: 10.34.34.102/24
• VLAN: 34 (tagged)
• Gateway: 10.34.34.1
• Bonding: LACP (802.3ad) using eth1 and eth2
• Connected to: leaf3 (eth1) and leaf4 (eth1)

Host3 (VTEP3 - L2 VXLAN on VLAN 40)

• Location: configs/host3-interfaces
• IP Address: 10.40.40.103/24
• VLAN: 40 (tagged)
• Bonding: LACP (802.3ad) using eth1 and eth2
• Connected to: leaf5 (eth1) and leaf6 (eth1)

Host4 (VTEP4 - L3 VXLAN in VRF gold on VLAN 78)

• Location: configs/host4-interfaces
• IP Address: 10.78.78.104/24
• VLAN: 78 (tagged)
• Gateway: 10.78.78.1
• Bonding: LACP (802.3ad) using eth1 and eth2
• Connected to: leaf7 (eth1) and leaf8 (eth1)

Interface File Structure

All host interface files follow this pattern:

auto lo
iface lo inet loopback

auto bond0
iface bond0 inet manual
    use bond
    bond-slaves eth1 eth2
    bond-mode 802.3ad
    bond-miimon 100
    bond-lacp-rate fast
    up ip link set $IFACE up

auto bond0.<vlan>
iface bond0.<vlan> inet static
    address <ip_address>
    netmask 255.255.255.0
    [gateway <gateway_ip>]  # Only for L3 VXLAN hosts
    vlan-raw-device bond0
    up ip link set $IFACE up

Key Configuration Points

Alpine Linux Bonding Syntax

• Uses use bond directive (specific to ifupdown-ng in Alpine Linux)
• LACP mode configured via bond-mode 802.3ad
• Fast LACP rate for quicker failover detection

VLAN Tagging

• VLANs are tagged by the hosts using subinterfaces (bond0.40, bond0.34, bond0.78)
• Switch ports are configured in trunk mode, NOT access mode
• This prevents layer 2/3 mismatches that would break VXLAN connectivity

Topology Integration

The topology file (evpn-lab.clab.yml) mounts these files using binds:

host1:
    kind: linux
    image: alpine:latest
    binds:
        - configs/host1-interfaces:/etc/network/interfaces

Testing Connectivity

L2 VXLAN (VLAN 40)

Host1 and Host3 should be able to ping each other:

# From host1
ping 10.40.40.103

# From host3
ping 10.40.40.101

L3 VXLAN (VRF gold)

Host2 and Host4 should be able to ping each other:

# From host2
ping 10.78.78.104

# From host4
ping 10.34.34.102

Verification Commands

On hosts - Check bonding status:

cat /proc/net/bonding/bond0
ip link show bond0
ip addr show bond0.<vlan>

On leaf switches - Check MLAG port-channels:

show mlag interfaces
show port-channel summary
show interfaces status

On leaf switches - Check VXLAN:

show vxlan vtep
show vxlan address-table
show bgp evpn route-type mac-ip
show bgp evpn route-type ip-prefix ipv4