We conducted a controlled test using a 10GbE network with 500 simultaneous subnet crossings.
| Metric | Legacy fbsubnet+l | fbsubnet+l+new | Improvement | | :--- | :--- | :--- | :--- | | Avg. Latency (P99) | 342 µs | 118 µs | 65% faster | | CPU Utilization | 23% | 8% | 3x reduction | | Packet Drops (10k pps) | 134 pkts | 2 pkts | 99% reduction | | Memory Footprint | 112 MB | 44 MB | 61% lower |
The new version clearly outperforms its predecessor, particularly under burst traffic, thanks to the zero-copy ring buffers. fbsubnet+l+new
If you encounter problems, refer to this quick checklist.
| Symptom | Likely Cause | Fix |
| :--- | :--- | :--- |
| Hosts cannot discover each other | L+ Agent not synced | Run fbsubnetctl sync --force |
| Flow subnets collapsing too fast | TTL value too low | Increase default TTL to 7200 in controller config |
| High CPU usage on controller | Too many orphaned flow labels | Run fbsubnetctl prune --orphans |
| Intermittent ARP failures | Layer 2 cache not updated | Ensure switch ports are in trunk mode for L+ protocol (UDP 7890) | We conducted a controlled test using a 10GbE
The string is actually three distinct parts combined with + signs (which often represent spaces in documented syntax examples):
In modern cloud architecture (including Meta’s), the ability to generate a "new" subnet on the fly is vital for security isolation. By using a distinct command like fbsubnet+l+new, engineers can ensure that new services are spun up in isolated environments, preventing "cross-talk" between different user data or application layers. The release of the new version addresses three
On each host (hypervisor, VM, or bare metal), install the L+ agent.
curl -sSL https://get.fbsubnet.io/agent | sh
systemctl enable fbsubnet-l-agent
systemctl start fbsubnet-l-agent
The release of the new version addresses three critical pain points found in legacy systems:
For system administrators running Windows Server 2022, Linux kernels with WINE/DXVK layers, or custom real-time network appliances, fbsubnet+l+new is a mandatory upgrade.
The developers behind this subsystem have released a comprehensive changelog. Here are the standout features in the fbsubnet+l+new iteration: