Symptom
After storing your user name and password for an SMB server in a keychain, the stored information does not work as you would expect when you connect to the server again. You must re-enter your user name and password.
Solution
Create an alias of the SMB share point. Follow these steps:
1. Click the Finder icon in the Dock.
2. Choose Go > Connect to Server.
3. Enter the SMB server address, and click Connect.
4. Select the desired share point.
5. Choose Go > Computer.
6. Drag the SMB volume from the Finder window to your desktop. The icon that appears on the desktop after you drag it will be an alias.
7. From the Finder window, select the SMB volume and choose File > Eject.
8. Double-click the alias created in step 6.
9. Enter your user name and password, then select Add to Keychain.
10. Click OK.
The next time you connect to this SMB volume using the alias, the keychain will work as expected.
Additional information
If you click the Computer button in a Finder window then select a volume, the Make Alias command is dimmed. This is normal behavior, because accounts other than root do not have permission to create new items in the Computer list. Dragging the volume to a place where you have permission allows you to make the alias, as you did in the steps above.