Replying to mark TOTAL OF ALL PREVIOUS POSTS IN THIS DISCUSSION as the SOLUTION. But please continue to post any questions/comments.
Various components on the DP4400 will fail to be to ping each other or be able to ping the local gateway, This can also impact the ability to ping interfaces from the production network.   This Knowledge article can help in the above issue,  Link : [URL]
DP4400 Network communication failures between components