Configuring LLT manually

Last published : Sep 11, 2026
VCS uses the Low Latency Transport (LLT) protocol for all cluster communications as a high-performance, low-latency replacement for the IP stack. LLT has two major functions.
It handles the following tasks:
  • Traffic distribution
  • Heartbeat traffic
To configure LLT over Ethernet, perform the following steps on each node in the cluster:
  • Set up the file /etc/llthosts.
See Setting up /etc/llthosts for a manual installation.
  • Set up the file /etc/llttab.
See Setting up /etc/llttab for a manual installation.
  • Edit the following file on each node in the cluster to change the values of the LLT_START and the LLT_STOP environment variables to 1:
/etc/default/llt
You can also configure LLT over UDP.
See Using the UDP layer for LLT.