notes/projects/gg/avahi_mdns-reflector/20250718-overview.md

Here's a structured summary of your network requirements and design, incorporating your latest updates and clarifications:

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Network Overview

1. VLANs and Subnets

VLAN	Subnet	Gateway IP	Avahi Server IP	mDNS Proxy IP
15	172.16.19.0/255.255.252.0	172.16.19.254	172.16.19.250	172.16.19.251
19	192.168.151.0/255.255.252.0	192.168.151.254	192.168.151.250	192.168.151.251
7	172.16.111.0/255.255.248.0	172.16.111.254	172.16.111.250	172.16.111.251

Note: All VLANs are routed via the Sophos XGS4300, which acts as the DHCP server for all VLANs.

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2. Avahi Server Configuration

• Local Avahi Servers:
  • VLAN 15: Runs Avahi on 172.16.19.250 for local discovery.
  • VLAN 19: Runs Avahi on 192.168.151.250 for local discovery.
  • VLAN 7: Runs Avahi on 172.16.111.250 for local discovery.
• Central Avahi Server (mDNS Proxy):
  • IPs: 172.16.19.251, 192.168.151.251, 172.16.111.251 (untagged interfaces for each VLAN).
  • Configuration:

    [reflector]
    enable-reflector=yes
    #reflect-ipv=no
    #reflect-filters=_airplay._tcp.local,_raop._tcp.local
    

  • Purpose: Acts as a central mDNS reflector to forward traffic between VLANs, enabling Apple devices in VLANs 15/19 to discover Apple TVs in VLAN 7.

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3. mDNS Proxy VM (Central Avahi Server)

• OS: Debian.
• Network Configuration:
  • Uses /etc/network/interfaces to assign static IPs for each VLAN (ending in .251).
  • Interfaces are untagged (virtual) for each VLAN.
• Function:
  • Forwards mDNS traffic between VLANs (e.g., _airplay._tcp.local, _raop._tcp.local).
  • Ensures Apple devices in VLANs 15/19 can discover Apple TVs in VLAN 7 via Bonjour.

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4. ESXi and VLAN Management

• Hyper-Visor: ESXi.
• vSwitch Configuration:
  • Each VLAN is assigned a virtual port group with the corresponding subnet.
  • VMs (Avahi servers, mDNS proxy, etc.) are assigned to the appropriate VLAN port group.
• IP Assignment:
  • VMs use static IPs (.250 for local Avahi servers, .251 for central Avahi server).

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5. Switch Configuration

• Switches: Managed Level 2 switches.
• IGMP Snooping:
  • Recommendation: Enable IGMP snooping on all switches.
  • Rationale:
    • While mDNS (Bonjour) uses UDP and not IGMP, other multicast services (e.g., 546/udp for DHCPv6, 80/443 for HTTP/HTTPS) may rely on IGMP.
    • IGMP snooping prevents unnecessary multicast traffic flooding, improving network efficiency.
  • Note: If only mDNS is used, IGMP snooping is not strictly required, but enabling it is beneficial for future scalability.

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Key Considerations

• Resource Allocation for VMs:
  • Avahi Servers (VLANs 15, 19, 7): Minimal resources (1 vCPU, 512MB RAM).
  • Central Avahi Server (mDNS Proxy): Slightly higher resources (2 vCPUs, 1GB RAM) due to traffic forwarding.
• Firewall Rules:
  • Ensure UDP ports 80, 443, 546/udp, 546/tcp are open between VLANs 15/19 and VLAN 7.
  • Allow mDNS traffic (UDP 5353) for Bonjour discovery.
• Testing:
  • Use avahi-browse on Apple devices to verify Apple TV discovery.
  • Test service ports (e.g., curl http://<AppleTV-IP>:80) to confirm connectivity.

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Summary of Design

• VLAN Isolation: Each VLAN operates independently with its own subnet and Avahi server.
• Central mDNS Proxy: Acts as a bridge for Bonjour discovery between VLANs, enabling cross-VLAN service discovery.
• Network Efficiency: IGMP snooping is enabled to optimize multicast traffic handling.
• Scalability: The design supports future additions (e.g., more Apple devices, services) without overhauling the architecture.

Let me know if you’d like a diagram or Debian interface configuration examples! 🚀