There are two alternatives to provide for the inter-domain trust:
Configure a Credential Mapping for Cross-Domain Security, using WLS admin console:
a. Click the name of your security domain (by default, myrealm).
b. Select Credential Mappings Tab and click on Default.
Enable Cross-Domain Security, using WLS admin console:
a. Click the name of the domain in the Domain Configurations section of the Home page.
b. Select Security > General
c. In the Excluded Domain Names field, enter the names of any domains that do not have cross-domain security enabled. Enter the names of these domains separated either by semicolons or line breaks.