Issue
When Sigma operates over a site-wide Ethernet network with multiple subnets—or when Sigma DNNs use ARCnet or Ethernet secondary LANs—global object values may not be received by controllers located on different subnets. This results in communication failures between controllers.
Product Line
Satchwell BAS & Sigma
Environment
Sigma Ethernet networks containing subnets.
Cause
Global values are broadcast messages that are not routed across third-party Ethernet routers. Without proper configuration, these messages are blocked, preventing communication between controllers on different subnets.
Resolution
To enable global data transmission across subnets, Link Addressing (LA) must be configured. This process encapsulates broadcast messages into IP packets, allowing them to traverse routers and reach the intended devices.
Refer to PIB 05.01.05-3 – Rules for Using Link Addressing for full technical guidance.
📎 Attachment: PIB050105_3 Link Addressing.pdf
Key Concepts
What is Link Addressing?
- Sigma uses broadcast messages for global data exchange.
- Routers block these broadcasts to prevent network flooding.
- Link Addressing converts broadcasts into directed IP packets.
Firmware Requirements
- Ensure controllers and DNNs are running firmware version 5s (controllers) and 5t (DNNs) or later.
- Earlier versions may not support Link Addressing reliably.
Configuration Commands (via Pocket Terminal)
LA+ <IP>— Add a Link AddressLA- <IP>— Remove a Link AddressLAD— Display all Link AddressesLAC— Clear all Link Addresses
⚠️ Maximum of 5 Link Addresses per device
⚠️ On older firmware, Link Addresses may be deleted when downloading theCO??.SETfile
Examples of Link Addressing Scenarios
1. Basic Two-Subnet Configuration
- Node 10:
LA+ 10.44.101.20 - Node 20:
LA+ 10.44.100.10 - Required for bidirectional global data exchange.
2. DNNs Bridging Subnets
- Node 100 (DNN):
LA+ 10.44.101.20 - Node 101 (DNN):
LA+ 10.44.100.10 - DNNs rebroadcast global messages to their subLANs.
3. Multi-Subnet Circular Configuration
- Treat the network as a circle.
- Link Addressing should be configured clockwise and anti-clockwise, but avoid loops unless using advanced group configurations.
4. Using DNNs for Re-Broadcasting
- Add DNNs to subnets with multiple controllers.
- Only DNNs need Link Addresses; they rebroadcast to all local controllers.
Advanced Configuration
Global Message Lifetime
- Each global message starts with a Life Time Count of 15.
- Each DNN hop decrements the count.
- Messages are discarded when the count reaches 0.
Large Networks (15+ Subnets)
- Use grouped DNNs with “Daisy Chain” Link Addressing.
- Interconnect groups with selected DNNs to form a resilient ring.
Monitoring and Maintenance
- Use Sigma Device Monitoring to ensure DNNs are operational.
- Monitor for DNN failures which can disrupt global data flow.
DNN Configuration for Re-Broadcasting
- Configure DNN as a router using Port 2.
- Add a new serial network in Sigma System Manager.
- No physical connection is needed on Port 2.
Best Practices
- Avoid loops unless using grouped DNNs.
- Limit global traffic to prevent network performance issues.
- Use DNNs to simplify Link Addressing in complex subnet environments.
