I saw this error message on a Cisco ASA 5540 today:
%ASA-3-210005: LU allocate connection failed
According to Cisco, this error means the standby unit was not able to create a new connection for stateful failover. The recommendation is to verify that the system has enough RAM.
# show memory Free memory: 987969608 bytes (92%) Used memory: 85772216 bytes ( 8%) ------------- ---------------- Total memory: 1073741824 bytes (100%)
As you can see, this system has a lot of free memory? So that's obviously not the issue.
I thought perhaps the problem was related to some sort of communication problem between the standby and active devices, but that wasn't the case either. I did a little in the Cisco Bug Toolkit and found CSCsh80889: LU allocate connection failed msg due to failed VPN flow replication.
The fix is to upgrade to a more recent version of Cisco ASA software.