🔗 Network Architecture¶

Overview¶

Tatbot uses a sophisticated dual-mode networking system that automatically adapts based on network conditions with seamless failover and automatic configuration management.

Principles¶

Automatic Mode Detection: Zero manual intervention for mode switches
Seamless Failover: Sub-20 second transitions between modes
Internet Resilience: Always-available internet access when possible
DNS Continuity: .tatbot.lan domains work in both modes
Self-Healing: Automatic DHCP renewal and configuration repair

Network Modes¶

Home Mode¶

Triggered when: Home LAN cable connected to switch-lan

DHCP: Home router (192.168.1.1) provides IP addresses
Gateway: 192.168.1.1 (home router)
DNS: rpi2 (192.168.1.99) forwards queries to home router
Internet: Full access via home network
Scope: Access to home computers (e.g., oop)

Edge Mode¶

Triggered when: Home LAN cable disconnected from switch-lan

DHCP: rpi2 (192.168.1.99) provides IP addresses
Gateway: ook (192.168.1.90) with WiFi NAT
DNS: rpi2 (192.168.1.99) with upstream to 1.1.1.1/8.8.8.8
Internet: Available via ook’s WiFi connection
Scope: Isolated tatbot network with optional internet

Components¶

rpi2: DNS/DHCP Controller¶

Role: Central network coordination
Services: dnsmasq with mode-aware configuration
Auto-Detection: Monitors home router availability every 20 seconds
DHCP Orchestration: Triggers automatic renewal on all nodes during mode switches

ook: Edge Gateway¶

Role: Internet gateway in Edge mode
NAT Setup: WiFi → Ethernet forwarding using iptables
IP Forwarding: Enabled with persistent rules
Failover: Provides internet when home network unavailable

Other Nodes (eek, hog, ojo, rpi1)¶

Configuration: Use rpi2 as DNS server (192.168.1.99)
DHCP Client: Accept leases from either rpi2 or home router
Auto-Renewal: Receive new network configuration automatically

Automation¶

Mode Detection¶

Trigger: Home router (192.168.1.1) reachability test
Frequency: Every 20 seconds via tatbot-mode-auto.service
Script: scripts/mode_auto_switcher_with_dhcp.sh

DHCP Renewal Orchestration¶

Automatic: Triggered on every mode switch
Method: SSH-based dhclient commands to all nodes
Parallel Execution: All nodes renewed simultaneously
Fallback: 5-minute lease timeout ensures eventual consistency

DNS Resolution¶

Tatbot Domains: Always resolves .tatbot.lan addresses
Internet Domains: Forwarded appropriately per mode
Static Entries: All tatbot devices have fixed .tatbot.lan names

IP Addressing¶

Static Reservations¶

ook:     192.168.1.90  # Gateway in Edge mode
eek:     192.168.1.97  # NFS server
hog:     192.168.1.88  # Robot control
ojo:     192.168.1.96  # AI inference
rpi1:    192.168.1.98  # Visualization
rpi2:    192.168.1.99  # DNS/DHCP server
camera1-5: 192.168.1.91-95
arms:    192.168.1.2-3

DHCP Ranges¶

Edge Mode: 192.168.1.2-254 (covers static reservations)
Home Mode: Delegated to home router

Config Files¶

config/network/dnsmasq/mode-edge.conf - Edge mode DNS/DHCP
config/network/dnsmasq/mode-home.conf - Home mode DNS forwarding
config/network/systemd/tatbot-mode-auto.service - Auto-detection service

Scripts¶

scripts/mode_auto_switcher_with_dhcp.sh - Main mode detection and switching
scripts/setup_nat_ook.sh - NAT configuration for ook
scripts/network_status.sh - Network diagnostics and status

Network Flow¶

Edge Mode Internet Path¶

Node → ook (192.168.1.90) → WiFi NAT → Internet

Home Mode Internet Path¶

Node → Home Router (192.168.1.1) → Internet

DNS Resolution Path (Both Modes)¶

Node → rpi2 (192.168.1.99) → [Home Router | Upstream DNS]

Monitoring¶

Status Checking¶

# Check current mode
ssh rpi2 "readlink -f /etc/dnsmasq.d/active.conf"

# Monitor mode switching
ssh rpi2 "sudo journalctl -u tatbot-mode-auto.service -f"

# Network status from any node
./scripts/network_status.sh

Troubleshooting¶

Mode Detection Issues: Check tatbot-mode-auto.service logs
DHCP Problems: Verify lease files and dnsmasq status
Internet Issues: Verify ook’s WiFi and NAT configuration
DNS Problems: Test resolution with nslookup <host>.tatbot.lan 192.168.1.99

Security¶

Network Isolation: Edge mode isolates tatbot from home network
Minimal Attack Surface: Only required ports and services exposed
Automatic Updates: Network configuration stays current without manual intervention
Failsafe Design: Degrades gracefully when components unavailable

Roadmap¶

VLAN Segmentation: Further isolate device types
Certificate Management: TLS for inter-node communication
Load Balancing: Multiple internet gateways in edge mode
Monitoring Dashboard: Real-time network status visualization