This just happened to me today. We had a point to point T1 circuit go down, and all I could see on the one end was:
DCD=down DSR=up DTR=up RTS=up CTS=up So, even though our CSU/DSU was powered up and connected to the routers serial interface with a good cable, we showed DCD down because the telco circuit was down. Mike W. Priscilla Oppenheimer wrote: > Here's the conclusion, since a few people have wondered about > it. By the > way, the question had to do with an external CSU/DSU. > > According to Cisco documentation, a down/down serial interface > means the > router interface cannot determine that CD has been asserted. As > mentioned > earlier, a CSU/DSU acts more like a DSU than a CSU and presents > a > synchronous signal to the router. The CSU/DSU must assert Data > Carrier > Detect (DCD or CD), Data Set Ready (DSR), and Clear to Send > (CTS). The > router, which is playing the DTE role, must assert Data > Terminal Ready > (DTR) and Request to Send (RTS). For all these control leads to > be > asserted, and for the router to recognize that they are > asserted, the > router and CSU/DSU hardware must be operational, and the > cabling must be > properly constructed. > > However, even if all hardware checks out, there are still cases > when the > interface may be down/down or flapping between up/up, up/down, > and > down/down. For example, some CSU/DSUs won't assert CD if the > link to the > carrier is having problems. In these cases, check the CSU/DSU > configuration. Make sure the right clocking, framing, and > encoding are > configured. If they are correctly configured, then call the > service > provider and work with the provider to isolate the problem. > > Priscilla Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=52792&t=47101 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
