Schemus LDAP directory searches fail with an Unknown Host or Connection Refused error

Products

• Email Security.cloud

Issue/Introduction

This Article describes a scenario while using the Schemus synchronization tool to search LDAP directory you receive an error code : Unknown Host or Connection Refused error.

Environment

Email Security.cloud

Cause

This is mainly caused by continuation references generated by the LDAP server for LDAP referrals to other parts of the directory. Referrals are often stored using the host name of the target LDAP server, which in the case of a self-referral, can be the name of the original host to which the connection was made. 

Resolution

If it is not necessary to follow the continuation references, this can be disabled from the Configuration Wizard. 

1 - Select the ''Data Source''  >> LDAP' page 

2 - Click the "Advanced" button

3 - Change "Continuation references" to ignore as shown below :

 

Note : On Active directory servers, it may be possible to avoid continuation references by connecting to port 3268 on the server rather than port 389. If it is necessary to follow the continuation references, the problem must be resolved either in the LDAP server or on the Client host.

For Unknown Host errors, the problem is most likely to be a failed DNS lookup. Ensuring DNS is working correctly on the computer from which Schemus is run should resolve the issue. Alternatively, the hostnames and IP addresses of the referred servers could be added to the hosts file. For Connection Refused errors, the problem is likely to be due to an incorrect referral information or a failure in the LDAP service on the referred server. Ensure that all the referred LDAP servers are running and/or update the referral entries on the LDAP server.