John, All, Actually, both router interfaces(DCE or DTE) will
show "down/down" if the both ports remain "administratively down".:-> Seriously, where I work since alot of our circuit are located in various locations within a number of our building we make use of what we call an Automatic Network Control Circuit (ANCC) system which logically maps our DCE devices from our Demarc to our NOC equipment area. Nonetheless, in answering Priscilla's question there is no one answer to the question. Basically, if the CSU/DSU is configured with a mismatch on the framing then the router port will come up/up. If the encoding is mismatched then this will cause the CSU/DSUs to lose "SYNC". Technically this will cause the router port to continually flap(up/down). When the CSU/DSU is configured correctly with the bandwidth(the configuration of the DSO slots(Nx64)) mismatch, this will allow the equipment to "SYNC" and the router ports will indicate up/up, however no data will traverse the link. John, is very correct in that the DTR on the DTE device has to be asserted for the DCE device and obviously for the DTE device to indicate an up/up. Howard, also brings up a good point in that framing and encoding does relate to layer one. Question? If encoding and framing are thought of as sub-layers of layer1, then what parallel can be drawn to other layered tecnologies that would allow/indicate an active interface without all the requirements being met. (i.e ISDN, ATM, and an IP interface) Chuck, I took your comments to heart and took down a number of of T1 customers to prove my noted few points.:-> I hope youre happy. Nigel >From: "John Neiberger" >Reply-To: "John Neiberger" >To: [EMAIL PROTECTED] >Subject: Re: serial interface down/down or up/down [7:47101] >Date: Fri, 21 Jun 2002 01:42:20 -0400 > >This isn't quite true. For example, a DCE router interface will be >down/down if DTR is not raised by the DTE device. I see this quite >often at work and faulty cabling is generally not the culprit. It's >almost always bad hardware in the DTE. > >John > >Michael L. Williams wrote: > > According to CCIE exam materials, the *only* time the serial will show > > down/down is when there is NO serial cable or a bad serial cable connected. > > So even if you have a misconfigured framing method, you should at least see > > up/down..... > > > > Mike W. > > > > "Bob Timmons" wrote in message > > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > >>I can't say I've ever seen a down/up condition. Up/Down perhaps. > >> > >>I'm sure there are exceptions, but it's my belief that the router doesn't > >>care about encoding, but rather a layer-1 connection to the dce/dte > > > > device. > > > >>If the router can 'talk' to the device on the other end of the cable, you > >>should get an up/x condition, where x would depend on the csu/dsu > > > > condition > > > >>of the line. > >> > >>I don't have a csu handy, otherwise I'd check that right now. I can do > > > > that > > > >>tomorrow morning (10:30 pm est here), but you may have an answer prior to > >>that... > >> > >> > >> > >>>Hi Priscilla, > >>> > >>>I have actually had this scenario (multiple times), but due to the > >> > > Telco's > > > >>>misconfiguration. > >>>Specifically we were expecting b8zs/esf. Unfortunately I can't confirm > >>>which was configured incorrectly, but I can confirm that going through > >>>all of the different combinations available at the router you will > >>>get all combinations on the serial interface (up/up, down/up and > >> > >>down/down). > >> > >>>I can also confirm, you will not establish connectivity, regardless. I > >>>believe > >>>either b8zs/esf or sf/ami are the only valid combinations. At least that > >> > >>is > >> > >>>all I've > >>>ever worked with. > >>> > >>>Hope this helps, > >>>-TV > >>> > >>> > >>>""Priscilla Oppenheimer"" wrote in message > >>>[EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > >>> > >>>>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. > >>>> > >>>>Thanks > >>>> > >>>>Priscilla > >>>> > >>>>________________________ > >>>> > >>>>Priscilla Oppenheimer > misconduct and Nondisclosure violations to [EMAIL PROTECTED] ------------------------------------------------------------------------ Send and receive Hotmail on your mobile device: Click Here Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=47130&t=47130 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
