I have a WIC-2T in a 2811 that is connected to an external CSU/DSU. The physical interface is up (CONN light is on), but it appears the protocol is down. The strange part is that if i shutdown the interface, then no shutdown to bring it back up, I can ping the interface for about 20 seconds. Then it goes down again and I'm back to square one. Anyone ever experienced this? What am i doing wrong??