Add comprehensive host interface configuration documentation

2025-11-30 08:21:24 +00:00
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+# 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:
+```yaml
+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:
+```bash
+# 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:
+```bash
+# From host2
+ping 10.78.78.104
+
+# From host4
+ping 10.34.34.102
+```
+
+## Verification Commands
+
+### On hosts - Check bonding status:
+```bash
+cat /proc/net/bonding/bond0
+ip link show bond0
+ip addr show bond0.<vlan>
+```
+
+### On leaf switches - Check MLAG port-channels:
+```bash
+show mlag interfaces
+show port-channel summary
+show interfaces status
+```
+
+### On leaf switches - Check VXLAN:
+```bash
+show vxlan vtep
+show vxlan address-table
+show bgp evpn route-type mac-ip
+show bgp evpn route-type ip-prefix ipv4
+```