Data Source Unavailable on Symantec Messaging Gateway (SMG)

Products

• Messaging Gateway

Issue/Introduction

When managing Symantec Messaging Gateway (SMG), system alerts play a critical role in maintaining service reliability. One such alert that administrators may encounter is: Data Source Unavailable

Upon further investigation, the following error message might be found in the diagnostic logs:
Failure connecting to data source, failed to resolve hostname for source: Active_Directory_Name

Cause

This issue typically stems from a DNS resolution failure—specifically, SMG is unable to resolve the hostname of the directory data service (DDS). This can occur when one or more DNS servers configured on SMG are either unreachable or misconfigured, resulting in a failure to resolve the Active Directory hostname.

Resolution

1. Verify Configured DNS servers on SMG:

Run the following command to list the DNS servers currently configured on your SMG system:
dns-control list
Ensure that all listed servers are correct and accessible from the SMG system.

2. Test DNS resolution:

For each DNS server listed, test whether it can successfully resolve the DDS hostname. Use the following command, replacing dns_ip_address and dds_host_name accordingly:
nslookup dds_host_name dns_ip_address
If any of the servers fail to resolve the hostname, there may be a configuration issue with that DNS server or it may be temporarily unavailable.

3. Use IP address instead of Hostname:

If DNS resolution cannot be restored immediately, a temporary workaround is to use the IP address of the DDS host instead of its hostname. This can be configured through the SMG interface:

• Navigate to Administration > Directory Integration

• Edit the data source configuration

• Replace the hostname field with the IP address of the DDS server