By default, when configuring LLT links over UDP, VCS (Veritas Cluster Server) automatically assigns Link1 to port 50000, Link2 to port 50001, and Link3 to port 50002, and so on.

This issue happens, when port 50000 is being used by other application. Hence, LLT link cannot register with that port.

From the netstat.txt of a vxexplorer output, we see that snmp.exe is using port 50000
 

When running lltstat -nvv, the problematic link does not even show up in the output. This is what the llttab file looks like:
 

Here is the output of lltstat -nvv. Link1 is not even listed there.
 

Hence, the workaround for this issue is either:

1. Do not let snmp.exe, or other processes, use port 50000.

OR

2. Assign LLT Link1 to use any port other than 50000. This can be done by reconfiguring the LLT heartbeat using the vcw.exe utility.

If option 2 is performed, and if port 50003 is used for Link1 instead, then the output will look like this:

LLT node information:

    Node                 State    Link  Status  Address

   * 0 abcdefg          OPEN

                                  Link2   UP      15.67.12.11

                                  Link1   UP      15.67.34.10

     1 hijklmn          OPEN

                                  Link2   UP      15.94.15.11

                                  Link1   UP      15.94.89.10

The corresponding llttab file would look as follows:
 

One of the LLT (Low Latency Transport) links are not listed or registered despite no apparent network connectivity issues. There is no specific error message, but when listing the links with the lltstat -nvv command, the problematic link is not listed.