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arista-evpn-vxlan-clab/docs/HOST_INTERFACE_CONFIGURATION.md
Damien 1080bf07bb Complete Lab Fixes - L2 and L3 VXLAN Fully Operational (#14) 
## Summary

This PR merges all fixes and improvements from the troubleshooting journey to make the Arista EVPN-VXLAN lab fully operational with both L2 and L3 VXLAN connectivity.

## What's Changed

### 🎯 Major Achievements
- ✅ **L2 VXLAN fully operational** - host1 ↔ host3 connectivity verified
- ✅ **L3 VXLAN fully operational** - host2 ↔ host4 connectivity verified (VRF gold)
- ✅ **LACP bonding working** - dual-homed hosts with proper Port-Channel negotiation
- ✅ **All BGP/EVPN sessions established** - complete underlay and overlay working

### 🔧 Infrastructure Fixes

#### BGP & Routing
- Added `ip routing` command to all spine and leaf switches
- Fixed duplicate BGP network statements on leaf3, leaf4, leaf7, leaf8
- Activated EVPN neighbors on spine switches
- Added loopback network advertisements to BGP

#### MLAG Configuration
- Configured MLAG peer-link in trunk mode (not access) for VLAN 4090/4091
- Added dual-active detection via management interface
- Configured virtual router MAC for MLAG pairs

#### Switch Port Configuration
- Port-Channel1 configured in **trunk mode** on all leaf switches
- Added `switchport trunk allowed vlan` for host VLANs (34, 40, 78)
- Removed `no shutdown` from Port-Channel interfaces

### 🖥️ Host Networking - Complete Redesign

#### Image Change
- **Old:** `alpine:latest` (had bonding syntax issues)
- **New:** `ghcr.io/hellt/network-multitool` (networking tools pre-installed)

#### LACP Bonding Configuration
Proper LACP setup following network-multitool best practices:
```yaml
- ip link add bond0 type bond mode 802.3ad
- ip link set dev bond0 type bond xmit_hash_policy layer3+4
- ip link set dev eth1 down
- ip link set dev eth2 down
- ip link set eth1 master bond0
- ip link set eth2 master bond0
- ip link set dev eth1 up
- ip link set dev eth2 up
- ip link set dev bond0 type bond lacp_rate fast
- ip link set dev bond0 up
```

#### VLAN Configuration
- **L2 VXLAN hosts (host1, host3):** VLAN 40 tagged on bond0
- **L3 VXLAN hosts (host2, host4):** VLANs 34 and 78 tagged on bond0

#### Routing Strategy
- Kept management default route (172.16.0.254 via eth0)
- Added **specific routes** for L3 VXLAN networks instead of default routes:
  - host2: `ip route add 10.78.78.0/24 via 10.34.34.1`
  - host4: `ip route add 10.34.34.0/24 via 10.78.78.1`

### 📁 Files Changed

#### Switch Configurations (Updated)
- `configs/spine1.cfg` - Added ip routing, EVPN activation
- `configs/spine2.cfg` - Added ip routing, EVPN activation
- `configs/leaf1.cfg` - Port-Channel trunk mode, VLAN config
- `configs/leaf2.cfg` - Port-Channel trunk mode, VLAN config
- `configs/leaf3.cfg` - Added ip routing, loopback ads, Port-Channel config
- `configs/leaf4.cfg` - Added ip routing, loopback ads, Port-Channel config
- `configs/leaf5.cfg` - Port-Channel trunk mode, VLAN config
- `configs/leaf6.cfg` - Port-Channel trunk mode, VLAN config
- `configs/leaf7.cfg` - Added ip routing, loopback ads, Port-Channel config
- `configs/leaf8.cfg` - Added ip routing, loopback ads, Port-Channel config

#### Topology (Updated)
- `evpn-lab.clab.yml` - Updated all host configurations with network-multitool image and proper LACP/VLAN setup

#### Documentation (New)
- `hosts/README.md` - Host interface configuration guide
- `hosts/host1_interfaces` - Interface file for host1 (not currently used, kept for reference)
- `hosts/host2_interfaces` - Interface file for host2 (not currently used, kept for reference)
- `hosts/host3_interfaces` - Interface file for host3 (not currently used, kept for reference)
- `hosts/host4_interfaces` - Interface file for host4 (not currently used, kept for reference)

## Testing & Verification

### ✅ L2 VXLAN (VLAN 40)
```
host1 (10.40.40.101) → host3 (10.40.40.103)
- Connectivity: VERIFIED ✓
- VXLAN tunnel: VTEP1 ↔ VTEP3
- MAC learning: Working via EVPN Type-2
```

### ✅ L3 VXLAN (VRF gold)
```
host2 (10.34.34.102) → host4 (10.78.78.104)
- Connectivity: VERIFIED ✓
- Ping results: 0% packet loss, TTL=62
- Routing: Via EVPN Type-5 through fabric
```

### ✅ Infrastructure Status
- BGP Underlay: All sessions ESTAB
- EVPN Overlay: All neighbors ESTAB
- MLAG: All 4 pairs operational
- Port-Channels: LACP negotiated on all hosts

## Related Issues

Fixes #1 - Lab deployment and configuration fixes
Fixes #2 - BGP EVPN neighbors stuck in Connect state
Fixes #3 - Ready for deployment with EVPN activation
Fixes #4 - Lab convergence in progress
Fixes #5 - BGP EVPN neighbors stuck in Active state
Fixes #11 - Host LACP bonding configuration
Fixes #13 - L3 VXLAN default route issue

## Key Technical Learnings

1. **Arista EOS requires explicit `ip routing`** before BGP can function
2. **MLAG peer-link must be trunk mode** to allow VLAN 4090/4091 traversal
3. **VLAN tagging location matters** - hosts tag, switches use trunk mode
4. **network-multitool image** superior to Alpine for LACP bonding
5. **Specific routes better than default routes** when management network present
6. **LACP rate fast** ensures quick negotiation with Arista switches

## Deployment

After merging, deploy with:
```bash
cd ~/arista-evpn-vxlan-clab
sudo containerlab destroy -t evpn-lab.clab.yml --cleanup
sudo containerlab deploy -t evpn-lab.clab.yml
```

No manual post-deployment configuration needed - everything works from initial deployment!

## Breaking Changes

⚠️ **Host image changed** from `alpine:latest` to `ghcr.io/hellt/network-multitool`
⚠️ **Host configuration completely redesigned** - old exec commands replaced

## Reviewers

@Damien - Please review and merge when ready

---

**This PR represents the complete troubleshooting journey and brings the lab to production-ready status with full L2 and L3 VXLAN functionality.** 🚀

Reviewed-on: #14
Co-authored-by: Damien <damien@arnodo.fr>
Co-committed-by: Damien <damien@arnodo.fr>
2025-11-30 10:24:29 +00:00

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Host Interface Configuration Guide

Overview

All four hosts in the lab use persistent interface configuration files mounted via ContainerLab's binds feature. This approach provides cleaner, more maintainable configuration compared to using exec commands.

Architecture

Dual-Homing with LACP Bonding

Each host is dual-homed to an MLAG pair of leaf switches:

  • host1: dual-homed to leaf1 + leaf2 (VTEP1)
  • host2: dual-homed to leaf3 + leaf4 (VTEP2)
  • host3: dual-homed to leaf5 + leaf6 (VTEP3)
  • host4: dual-homed to leaf7 + leaf8 (VTEP4)

VLAN Configuration

Hosts handle VLAN tagging using sub-interfaces on the bond:

Host VLAN IP Address Purpose VRF
host1 40 10.40.40.101/24 L2 VXLAN test default
host2 34 10.34.34.102/24 L3 VXLAN test gold
host3 40 10.40.40.103/24 L2 VXLAN test default
host4 78 10.78.78.104/24 L3 VXLAN test gold

Interface Files Structure

Each host has a configuration file in hosts/ directory:

  • hosts/host1_interfaces → mounted to /etc/network/interfaces in host1
  • hosts/host2_interfaces → mounted to /etc/network/interfaces in host2
  • hosts/host3_interfaces → mounted to /etc/network/interfaces in host3
  • hosts/host4_interfaces → mounted to /etc/network/interfaces in host4

Interface Configuration Format

Example: host1_interfaces

auto lo
iface lo inet loopback

# Bond interface with LACP (802.3ad)
auto bond0
iface bond0 inet manual
    bond-mode 4
    bond-miimon 100
    bond-lacp-rate 1
    bond-slaves eth1 eth2

# VLAN 40 on bond0
auto bond0.40
iface bond0.40 inet static
    address 10.40.40.101
    netmask 255.255.255.0
    vlan-raw-device bond0

Key Parameters Explained

Bond Configuration:

  • bond-mode 4: LACP (802.3ad) mode - requires LACP on switch side
  • bond-miimon 100: Link monitoring interval (100ms)
  • bond-lacp-rate 1: Fast LACP (1 second intervals)
  • bond-slaves eth1 eth2: Physical interfaces in the bond

VLAN Sub-interface:

  • bond0.40: VLAN interface notation (bond0.VLAN_ID)
  • vlan-raw-device bond0: Parent interface for VLAN
  • Static IP configuration with address/netmask

Deployment Process

When ContainerLab starts a host:

  1. Mount interface file via binds
  2. Install packages: apk add ifupdown bonding vlan
  3. Load kernel modules:
    • modprobe bonding - enables LACP bonding
    • modprobe 8021q - enables VLAN tagging
  4. Bring up interfaces: ifup -a reads /etc/network/interfaces

Switch Configuration Requirements

For proper LACP operation, leaf switches must have:

interface Port-Channel1
   description host-X
   switchport mode trunk
   switchport trunk allowed vlan <vlan-id>
   mlag 1
   port-channel lacp fallback timeout 5
   port-channel lacp fallback individual
   no shutdown

interface Ethernet1
   description host-X-link1
   channel-group 1 mode active
   lacp timer fast
   no shutdown

Critical settings:

  • port-channel lacp fallback: Required for ContainerLab timing
  • lacp timer fast: Matches host's fast LACP rate
  • no shutdown: Must explicitly enable Port-Channel interface

Advantages of This Approach

  1. Persistence: Configuration survives container restarts
  2. Clarity: Single file shows complete network config
  3. Maintainability: Easy to modify VLAN assignments
  4. Production-like: Mirrors real-world dual-homing scenarios
  5. Clean deployment: No manual post-deployment fixes needed

Testing Connectivity

L2 VXLAN (same VLAN)

# host1 (VLAN 40) → host3 (VLAN 40)
docker exec clab-arista-evpn-fabric-host1 ping -c 4 10.40.40.103

L3 VXLAN (inter-VRF)

# host2 (VLAN 34, VRF gold) → host4 (VLAN 78, VRF gold)
docker exec clab-arista-evpn-fabric-host2 ping -c 4 10.78.78.104

Troubleshooting

Verify bond status on host

docker exec clab-arista-evpn-fabric-host1 cat /proc/net/bonding/bond0

Check VLAN interface

docker exec clab-arista-evpn-fabric-host1 ip addr show bond0.40

Verify LACP on switch

ssh admin@clab-arista-evpn-fabric-leaf1 "show port-channel 1 detailed"

References

  • Alpine Linux ifupdown-ng documentation
  • Linux bonding documentation: /usr/src/linux/Documentation/networking/bonding.txt
  • Arista MLAG configuration guide
  • srl-labs/srl-evpn-mh-lab (reference implementation)
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