Error: "Failed to resolve outbound addresses 'servername.example.com:443;SMP01:443;servername.example.com:4726;servername:4726' , error: No such host is known (11001)"

Products

• IT Management Suite
• Client Management Suite

Issue/Introduction

The following error was noticed occurring multiple times when a client machine is trying to reach out to the SMP server:

[65:IN: 135C -> 0, RECV: EA3A7027][17A8ED60010, WS: DE8] Failed to resolve outbound addresses '<servername>.example.com:443;<servername>:443;<servername>.example.com:4726;SMP01:4726', error: No such host is known (11001)
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Date: 1/13/2021 8:55:53 AM, Tick Count: 522204781 (6.01:03:24.7810000), Size: 489 B
Process: AeXNSAgent.exe (15148), Thread ID: 20116, Module: AeXNetComms.dll
Priority: 1, Source: SMAIO.SSLProxy.Socket

The following warnings like these are also seen:

Warning 1:

[65:IN: 135C -> 0, RECV: EA3A7027][17A8ED60010, WS: DE8] Failed to resolve all target addresses from list '<servername>.example.com:443;<servername>:443;<servername>.example.com:4726;<servername>:4726', error: No such host is known (11001)
-----------------------------------------------------------------------------------------------------
Date: 1/13/2021 8:55:53 AM, Tick Count: 522204781 (6.01:03:24.7810000), Size: 501 B
Process: AeXNSAgent.exe (15148), Thread ID: 20116, Module: AeXNetComms.dll
Priority: 2, Source: SMAIO.SSLProxy.Socket

Warning 2:

[65:IN: 135C -> 0, RECV: EA3A7027][17A8ED60010, WS: DE8] Failed to resolve target address '<servername>.example.com:4726' from list '<servername>.example.com:443;<servername>:443;<servername>.example.com:4726;<servername>:4726', the address will be ignored, error: No such host is known (11001)
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Date: 1/13/2021 8:55:53 AM, Tick Count: 522204781 (6.01:03:24.7810000), Size: 546 B
Process: AeXNSAgent.exe (15148), Thread ID: 20116, Module: AeXNetComms.dll
Priority: 2, Source: SMAIO.SSLProxy.Socket

Environment

ITMS 8.5, 8.6

Cause

1. The agent can switch from HTTP to HTTPS in case CEM policy is enabled or a persistent connection is enabled. Both these features require an agent to work over HTTPS so it switches to HTTPS. That's by design.
2. The Agent Communication Profile hosts below - host with 4726 port should not be added manually, CEM connection uses settings from CEM policy, 4726 port is not needed in the profile and can only harm because an agent may try connecting to port 4726 in case it could not connect to port 443. Please remove 4726 from the profile.
   1. <servername>.example.com:80;altrsns-01:80
   2. <servername>.example.com:443;<servername>:443;<servername>.example:4726;<servername>-01:4726

Resolution

Prior to the messages above, you may see something like this:

[17A8ED60870, WS: 10B4] Connecting to '<servername>.example.com:443;<servername>:443;<servername>.example.com:4726;<servername>:4726' asynchronously, timeout: 60000 ms
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Date: 1/13/2021 8:55:43 AM, Tick Count: 522195062 (6.01:03:15.0620000), Size: 443 B
Process: AeXNSAgent.exe (15148), Thread ID: 16180, Module: AeXNetComms.dll
Priority: 4, Source: SMAIO.WSTransport.ReconnectCallback

The above message says that the Agent Communication Profile contains two hosts, one with SSL port and the second is with CEM port.

That 4726 record forces an agent to connect to the server via port 4726 directly rather than port 443.

There should be no CEM ports in the Agent Communication Profile, the alternative hostnames are supposed to be there:

1. Under SMP Console > Settings > Agents/Plug-ins > Symantec Management Agent > Symantec Management Agent Communication profiles, Remove any reference for the CEM port used (by default port 4726). Save changes.

The Servers list in an Internet Gateway is the one that tells the agents to use port 4726 for any SMP server listed when they need to connect.

Note: If there is a Site Server that is acting as an Internet Site Server, then this port 4726 will be added to its Site Server Communication Profile.

Additional Information

191076 "Unable to connect via CEM mode. Error note: Failed to resolve host name to IP address"