SQL5043N Support for one or more communications protocols failed to start successfully.

The full error message on db2start was :

 SQL5043N  Support for one or more communications protocols failed to start successfully. However, core database manager functionality started successfully.

 
 
The main reasons are normally:

1)       DB2COMM profile not properly defined

2)       Mismatch between the DB2COMM variable and database manager e.g SVCENAME

3)       Mismatch between the services file entry and value on the SVCENAME database configuration manager

 Use db2 get dbm cfg   to view SVCENAME and compare against the /etc/services file.

I check the /etc/services file and it was different to the entry on : 

 db2 get dbm cfg   | grep SVCENAME

1)       I changed the /etc/services entry to match the SVCENAME

2)       Restarted the DB2 instance and the problem disappeared