Path: utzoo!utgpu!watmath!att!tut.cis.ohio-state.edu!husc6!rice!sun-spots-request From: menges@menges.cs.unc.edu (John Menges) Newsgroups: comp.sys.sun Subject: Re: Frequent ie0: No carrier messages Keywords: SunOS Message-ID: <601@brazos.Rice.edu> Date: 28 Jul 89 12:56:31 GMT Sender: root@rice.edu Organization: Sun-Spots Lines: 49 Approved: Sun-Spots@rice.edu X-Sun-Spots-Digest: Volume 8, Issue 88, message 2 of 16 In our experience (with Siecor's fiber-optic ethernet, especially the passive one) this is usually caused by collisions which for some reason go undetected or are not reported to the Sun properly. I suspect what's happenning is that the Sun ethernet hardware is monitoring the signal it's transmitting (on its receive pair) to make sure it conforms to the manchester encoding rules. If it doesn't, and no collision is reported, it reports that it has lost carrier. Under older Sun operating systems, the output errors column of "netstat -i" incremented each time a "no carrier" message was printed. Later versions of the operating system didn't report "no carrier" messages each time the event occurred. I suspect Sun got tired of hearing complaints and changed the system so it only reported some of the errors (e.g., only if they happen twice in a row or some such). There are various problems that can cause "no carrier" messages (actually, you should monitor output errors instead, as this is now more reliable). Our biggest contributor was the passive fiber system. It doesn't work because collisions are not detected reliably. The fiber ethernet system vendors now recognize this and have switched to active stars. Other contributors are faulty transceivers and transceiver cables that are too long (50 Meters is really the limit). You might also have a faulty tranceiver cable, or the Sun ethernet card might be defective. We have eliminated nearly all output errors from our system of about 100 Suns, except for the Sun-4s, which report output errors no matter what we do. By the way, lots of output errors can make your nfd daemons hang. Watch out for this. The problem was so big here with the passive stars that the grad students, when voting for the year's departmental T-shirt, chose: ie: no carrier ie: no carrier ie: no carrier ie: no carrier ie: no carrier ie: no carrier I have some shell scripts that collect netstat statistics from all our suns twice a day, and generate reports sorted on various fields (e.g., output errors, descending). This helped us to know where our worst problems were, and we attacked them first. Let me know if you want the scripts.