OHS -Failure To Connect To WebLogicHost On IPV6 Entry Causes Permanent Switch To IPV4 Resolution (Doc ID 2728707.1)

Last updated on NOVEMBER 17, 2023

Applies to:

Symptoms

Backend WLS server configured to listen on IPV6 only.  Intermittently Oracle HTTP Server(OHS) mod_wls_ohs plugin connections switch from IPV6 and stays at IPV4 resulting in CONNECTION_REFUSED errors.

Following are 3 conditions causing plugin to switch from IPV4 to IPV6.  In all cases OHS need to be restarted to resolve the issue.

1. WLDNSRefreshInterval not set. Backend WLS server running without issue.
   -Plugin initial DNS resolved to IPv6 address.
   -At some point plugin switched permanently to IPv4 for connection to backend WLS servers.

2. WLDNSRefreshInterval not set. WLS backend server is restarted.
    -As expected IPV6 connections failed with CONNECTION_REFUSED.
    -By design plugin use the next available IP address permanently (which is IPV4).

3. Specify WLDNSRefreshInterval, DNS lookup is performed based on WLDNSRefreshInterval period.
    -Plugin switch permanently from IPv6 address to IPv4 address. 

Cause

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