I've seen both down/down and up/down in real-world scenarios. The difference between the two seemed to be the intelligence of the CSU/DSU.
With a recent Adtran unit, it goes down/down - if the CSU is down, it takes down the DSU. I did not delve into the configuration to see if this behavior could be changed. A very old Black Box unit that I've played with will happily keep the DSU up regardless of the state of the CSU. This one was configured with DIP switches, and I didn't see a way to change the behavior. Priscilla Oppenheimer wrote: > > I guess the question is too hard for a practice test if NOBODY can answer > it!? > > Here's the thing: Cisco says that a down/down interface means the router > interface is not sensing a Carrier Detect signal (that is, the CD is not > active). > > Now, from my studies of V.35 I know that data carrier detect (DCD or CD) > comes from the DCE side of the V.35 link, carried on pin 8, yadda, yadda. > It comes from the data interface on the DSU side of the CSU/DSU. > > If the router is correctly connected to the CSU/DSU, will it see CD or does > the answer depend on whether the CSU/DSU is also correctly talking to the > telco? > > Does "carrier detect" mean literally what it sounds like it means? Would > the CSU/DSU not assert CD if there was a problem on the telco side? And > hence the router wouldn't see CD and would say the interface was down/down. > > Not something I can easily test. Maybe I better simplify the question. ;-) > > Priscilla > > At 06:34 PM 6/20/02, Priscilla Oppenheimer wrote: > >Hi Group Study, > > > >While writing some questions for a practice test, I found myself > >questioning what I thought was the right answer. Here's the scenario: > > > >A Cisco router serial interface is correctly connected with a good V.35 > >cable to the data port on the DSU side of a CSU/DSU. The CSU/DSU has been > >misconfigured for the framing method (SF instead of ESF). The framing > >doesn't match what the provider is using. (The question refers to a CSU/DSU > >that is external to the router, not one that is built into the router.) > > > >Will the Cisco router serial interface be down/down or up/down? > > > >And, would the answer be any different if the question has to do with > >misconfiguring the encoding (AMI versus B8ZS)? > > > >If you have real-world experience with this, that would help. I have read > >the Cisco documentation and the troubleshooting charts, etc. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=47159&t=47101 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
