ALBD network connection errors in log on the client machine

Technote (troubleshooting)

Problem(Abstract)

This technote discusses albd contact errors that may appear in the ALBD log for IBM Rational ClearCase when port blocking is enabled on the router between the client and the server.

Symptom

The following errors may be seen in the ALBD log on a ClearCase client.

Error: Unable to contact albd_server on host 'Server_Hostname'

albd_contact call failed: RPC: Unable to receive; errno = [WINSOCK] Connection reset by peer

Note: Server_Hostname is referring to the VOB server for your site.

No related errors are seen on the logs on the VOB server. Using a network protocol analyzer, such as Microsoft Network Monitor or Wireshark , reveals that the client has sent out packets, but a response from the server is never received.

Cause

This behavior can be caused by enabling port blocking on a router. Port 371 and any port above 1024 are required to be open for reliable ClearCase communication. The ALBD process dynamically assigns ports in this range to its child processes, so if any of these processes attempt to communicate through a blocked port, they will not receive a response.

Resolving the problem

Currently, there is no way to limit the ports that the ALBD assigns so all ports between 1024 to 65534 along with port 371 must be open for reliable communication between ClearCase servers and clients.

Enabling port blocking on a router is similar to configuring a port-based firewall, see technote 1117638 that discusses Firewalls and ClearCase.

Consult your router's documentation or your systems administrator for information on opening up the correct ports.

Change request, (RFE) RATLC00608200, has been submitted to allow ClearCase to be configured to use CLEARCASE_MIN_PORT and CLEARCASE_MAX_PORT environment variables when blocking ports through a router.

Note: It is possible to limit the port range used by the shipping server but setting this may cause problems with other ClearCase processes trying to communicate from or to this system.

Refer to the Store-and-forward through a firewall section of the IBM Rational ClearCase MultiSite Administrator's guide for further information.

Related information

Troubleshooting ALBD startup errors
Firewalls and ClearCase
About CLEARCASE_MIN_PORT and CLEARCASE_MAX_PORT

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