The team stuck up in imbroglio where the l2tpv3 tunnel never torn down even after shutting down of physical sub-interface. There after lot of test were made but all in vein. The problem came with the SB13 ios but the opposite side was using different vendor equipment. The problem states that when the interface was shut down, no stop ack was sent to the remote peer, it is same as keepalives used in gre tunnel to get it torn. Still we are not able to find exact RCA except the IOS bug.