UniFi Chromecast Inter‑VLAN Configuration Guide
This document is a basic configuration guide for Chromecast devices across VLANs in a UniFi environment.
It was configured on a UniFi Dream Machine Pro (UDM Pro) with UniFi switches and access points.
Network Model
- User VLAN
- Phones, laptops, tablets
- IoT VLAN
- Chromecast devices
- Android TV / Google TV devices
- Chromecast and Android TV receivers do not support WPA2‑Enterprise or 802.1X
- Use WPA2‑PSK Wi‑Fi or wired Ethernet without port authentication
- Client isolation / AP isolation must be disabled
- Receivers require outbound HTTPS (TCP 443) access to Google Cast services
Required Ports and Protocols
Discovery (Multicast)
Chromecast uses multicast for discovery, not for streaming.
| Protocol | Destination | Port | Purpose |
|---|---|---|---|
| UDP | 224.0.0.251 | 5353 | mDNS (primary discovery) |
| UDP | 239.255.255.250 | 1900 | SSDP / DIAL |
mDNS is link‑local and does not cross VLANs unless explicitly forwarded.
Control & Session Setup (Unicast)
These ports are required for pairing, control, and casting initiation:
| Protocol | Port |
|---|---|
| TCP | 8008 |
| TCP | 8009 |
| TCP | 8443 |
Media & Mirroring (Unicast)
These ports are required for screen mirroring, tab casting, and local media:
| Protocol | Port(s) | Notes |
|---|---|---|
| UDP | 10008 | Required for mirroring |
| UDP | 32000–61000 | Dynamic RTP/RTCP media streams |
Important: Internet streaming (YouTube, Netflix, Spotify) may work without these ports. Mirroring will fail unless they are allowed.
UniFi mDNS Configuration
Enable mDNS on
- User VLAN
- IoT VLAN
Restrict mDNS services to ONLY
- Android TV Remote
- DNS Service Discovery
- Google Chromecast
This allows discovery while avoiding multicast noise and VLAN leakage.
IGMP Snooping Configuration
IGMP Snooping helps with overall connection stability.
Enable IGMP Snooping on
- User VLAN
Recommended settings
- Auto Querier Selection
- Fast Leave
- Auto Unknown Traffic Handling
This helps
- Prevents multicast flooding
- Keeps group membership alive
- Eliminates pixelation and delayed joins
Notes
- IGMP snooping is not a replacement for mDNS forwarding
- Do not rely on flooding
Firewall Rule Design
Recommended approach
- Scope rules to Chromecast / Android TV IPs
- Use static dhcp reservations
- Allow only required ports
- Avoid “allow all UDP” rules
Validation Checklist
- Chromecast appears across VLANs
- Casting starts immediately
- Screen mirroring works
- No pixelation or stutter
If mirroring fails:
- Check UDP 10008
- Check UDP return traffic
- Verify IGMP group membership
Common Issues
| Symptom | Likely Cause |
|---|---|
| Device appears but won’t connect | TCP 8009 blocked |
| Streaming works, mirroring fails | UDP 10008 blocked |
| Random stutter / pixelation | IGMP snooping missing or mis‑placed |
| Discovery intermittent | mDNS too broad or not forwarded |
Final Notes
Verified working on:
- UniFi Dream Machine Pro
- UniFi Layer 3 switches (IGMP snooping enabled)
- Wireless Chromecast / Android TV
- Inter‑VLAN routing with firewall enforcement