
### **Comprehensive Project Plan for VLAN Bridging with mDNS Proxy and Avahi Servers**

---

### **1. Project Overview**
**Objective**: Enable Apple devices in VLAN 15 and 19 to discover Apple TVs in VLAN 7 via Bonjour (mDNS) **without** requiring Layer 3 switches or VLAN routing on the Sophos firewall.  
**Key Requirements**:
- **VLANs**: Student (15), Teacher (19), AppleTV (7).
- **Subnets**:  
  - VLAN 15: `172.16.19.254/255.255.252.0`  
  - VLAN 19: `192.168.151.254/255.255.252.0`  
  - VLAN 7: `172.16.111.254/255.255.248.0`  
- **Services**: Bonjour (mDNS), HTTP/HTTPS (80,443), DHCP (546/udp, 547/udp), and other protocols.
- **Tools**:  
  - **Sophos XGS4300**: DHCP server, firewall.  
  - **ESXi**: Hypervisor for VMs.  
  - **Debian VMs**: Avahi servers, mDNS proxy.  
- **Switches**: Level 2 (no IGMP snooping).  
- **VM IPs**: `.250` in each VLAN (e.g., `172.16.19.250`, `192.168.151.250`, `172.16.111.250`).  

---

### **2. Network Architecture Design**

#### **A. VLAN Configuration (ESXi vSwitch)**
- **vSwitch Setup**:  
  - Create a **vSwitch** (e.g., `vSwitch0`) with **VLAN tags** for each VLAN (15, 19, 7).  
  - Assign **VMs** to this vSwitch with appropriate VLAN tags.  
- **VM Interfaces**:  
  - Each **Avahi server VM** and **mDNS proxy VM** will have **one virtual NIC per VLAN** (e.g., VLAN 15, VLAN 19, VLAN 7).  
  - Ensure **untagged interfaces** for management (optional).  

#### **B. VM Resource Allocation**
- **Avahi Server VMs**:  
  - **RAM**: 1GB (minimal, as Avahi is lightweight).  
  - **CPU**: 1 core.  
  - **Storage**: 10GB (for OS and logs).  
- **mDNS Proxy VM**:  
  - **RAM**: 2GB (to handle traffic forwarding).  
  - **CPU**: 2 cores.  
  - **Storage**: 20GB (for logs and configurations).  

#### **C. IP Addressing**
- **Avahi Servers**:  
  - VLAN 15: `172.16.19.250`  
  - VLAN 19: `192.168.151.250`  
  - VLAN 7: `172.16.111.250`  
- **mDNS Proxy**:  
  - Assign a **static IP** (e.g., `172.16.111.251`) in VLAN 7 (or use a management VLAN if needed).  

---

### **3. Software and Configuration**

#### **A. Avahi Servers (Per VLAN)**
- **OS**: Debian 12 (Bookworm).  
- **Installation**:  
  ```bash
  apt update && apt install avahi-daemon avahi-utils
  ```
- **Configuration (`/etc/avahi/avahi-daemon.conf`)**:
  - Ensure `host-name` is set to the VM's hostname (e.g., `avahi15`).  
  - Set `domain-name` to the local domain (e.g., `local`).  
- **Service Announcement**:
  - Place service files in `/etc/avahi/services/` for Apple TVs (e.g., `apple-tv.service`).  
  - Example `apple-tv.service`:
    ```xml
    <service>
      <type>_http._tcp</type>
      <subtype>_apple-tv._sub</subtype>
      <port>80</port>
      <host>apple-tv.local</host>
    </service>
    ```

#### **B. mDNS Proxy (VM)**
- **Software**: Use **`mdnsproxy`** (not `dnsmasq`) for mDNS forwarding.  
- **Installation**:
  ```bash
  apt update && apt install mdnsproxy
  ```
- **Configuration (`/etc/mdnsproxy.conf`)**:
  - Define **forwarding rules** between VLANs:
    ```ini
    [forward]
    172.16.19.250 192.168.151.250 172.16.111.250
    192.168.151.250 172.16.19.250 172.16.111.250
    172.16.111.250 172.16.19.250 192.168.151.250
    ```
  - Ensure **UDP port 5353** is open for mDNS traffic.  
- **Firewall Rules (Sophos XGS)**:
  - Allow **UDP port 5353** between VLAN 15, 19, and 7.  
  - Allow **TCP/UDP ports 80, 443, 546, 547** for service access.  

---

### **4. Firewall Configuration (Sophos XGS4300)**
- **DHCP Server**:  
  - Assign IPs to VLANs 15, 19, and 7.  
  - Ensure **IP ranges** match the subnets (e.g., VLAN 15: `172.16.19.252-254`).  
- **Firewall Rules**:  
  - **Allow** traffic between VLANs 15, 19, and 7 via the mDNS proxy.  
  - **Deny** direct communication between VLANs (to enforce proxy routing).  
  - **Allow** **UDP 5353** and **TCP/UDP 80, 443, 546, 547** for service discovery and access.  

---

### **5. Testing and Validation**
- **Step 1**: Verify **VLAN tagging** on ESXi vSwitch. Use `ovs-ofctl dump-ports` to confirm VLAN tags.  
- **Step 2**: Test **mDNS traffic** with `tcpdump` on the mDNS proxy VM:  
  ```bash
  tcpdump -i eth1 port 5353
  ```
- **Step 3**: Use **Bonjour tools** (e.g., `dns-sd`) to discover services:  
  ```bash
  dns-sd -B _http._tcp local
  ```
- **Step 4**: Ensure **Apple devices** can access services via the proxy.  
- **Step 5**: Monitor **firewall logs** for denied traffic to confirm proxy routing.  

---

### **6. Potential Hurdles and Solutions**
| **Hurdle** | **Solution** |
|------------|--------------|
| **Level 2 Switches**: No IGMP Snooping | **mDNS proxy** bridges VLANs, so multicast traffic is handled by the proxy. |
| **Firewall Rules**: Blocking inter-VLAN traffic | **Allow traffic via the proxy** (UDP 5353) and ensure services are accessible via ports 80, 443, etc. |
| **VM IP Conflicts** | Assign **static IPs** in each VLAN (e.g., `.250`) to avoid DHCP conflicts. |
| **mDNS Proxy Not Forwarding** | Verify `mdnsproxy` configuration and ensure VMs are connected to all VLANs. |
| **Service Discovery Failures** | Test with `dns-sd` and ensure Avahi servers are correctly configured. |

---

### **7. Resource Recommendations**
- **ESXi Host**:  
  - At least 8GB RAM, 4 cores.  
  - Ensure **vSwitch** is configured with VLAN tags.  
- **VMs**:  
  - **Avahi Servers**: 1GB RAM, 1 core.  
  - **mDNS Proxy**: 2GB RAM, 2 cores.  
- **Storage**:  
  - Allocate 10-20GB per VM for OS, logs, and service files.  

---

### **8. Final Notes**
- **Scalability**: Add more Avahi servers if needed, but ensure the mDNS proxy can handle increased traffic.  
- **Monitoring**: Use **Prometheus/Grafana** to monitor traffic and resource usage.  
- **Documentation**: Document VLAN IPs, VM configurations, and firewall rules for future maintenance.  

---

### **9. Has Anything Been Missed?**
- **No**: All requirements are addressed, including VLAN isolation, mDNS bridging, and service accessibility.  
- **Optional Enhancements**:  
  - Add **load balancing** for the mDNS proxy.  
  - Use **SNMP** to monitor switch traffic.  
  - Implement **failover** for critical services.  

---

### **10. Conclusion**
This setup is **feasible** and **robust** for your requirements. The key is ensuring the **mDNS proxy** is correctly connected to all VLANs via the ESXi vSwitch, and the **Sophos firewall** allows only traffic via the proxy. With proper testing and configuration, Apple devices in VLANs 15 and 19 will discover Apple TVs in VLAN 7 via Bonjour, and services will be accessible via the required ports. 🚀