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Mysterious Duplicate IP addresses
All machines on our 192.168.206.x subnet (mostly Mac's, with Windows servers) got the IP conflict message when they started up in the morning. We do have a linux dhcp server running on that subnet, but it only hands out 2 IP addresses for barcode guns, and those are given the IP based on their MAC address, so each barcode gun always gets the same IP and can move to other buildings without reconfiguring them, as they run in dhcp mode.
| Title | Date | Comments | |||
|---|---|---|---|---|---|
| Connect delete bug | 2012 12 | ||||
| - This is an unusual bug in the Kerio Connect 8 Web Client that few users are likely to see. - | |||||
| Simple debugging with Kerio Control | 2012 11 | ||||
| - An easy way to use Control as a network sniffer by creating useless rules and adding Accounting logging. - | |||||
| Understanding X-Loop forwarding headers | 2012 11 | ||||
| - How the X-Loop header works and how Cpanel apparently breaks it. - | |||||
| Filtering and separating Kerio Control Debug logs | 2012 10 | ||||
| - Kerio debug logs can contain a lot of extraneous noise. Use a script like this to separate the wheat from the chaff - | |||||
| Troubleshooting anti-spoofing messages | 2012 10 | 2012/11/18 TonyLawrence | |||
| - Is this network congestion or some other problem? Can you see what is confusing me? Join me in a network troubleshooting problem. - | |||||
| Troubleshooting Kerio Control installation | 2012 10 | ||||
| - Setting up Kerio control is usually very easy. If you do experience problems, this guide can help. - | |||||
| Notes on Kerberos troubleshooting (Kerio) | 2012 09 | 2012/09/18 TonyLawrence | |||
| - These are some notes on troubleshooting Kerberos, specifically in the context of Kerio directory service authentication. - | |||||
| Kerio Connect crash dumps and the kassist Tool | 2012 09 | ||||
| - Kerio Connect crashes are rare, but if it does happen, this article will help you understand what to do. - | |||||
| Moving an old SCO Unix Filepro box | 2012 08 | 2012/09/18 TonyLawrence | |||
| - She thought she wanted to put a public IP address on this old SCO box. Fortunately, no one was able to help her with that. - | |||||
| Setting up a multihomed Kerio Mailserver in a DMZ | 2012 08 | ||||
| - Missing a simple checkbox in the GUI network configuration prevented the mailserver from working in the DMZ - | |||||
| Recovering from a bad Kerio Mailserver crash | 2012 07 | 2012/09/17 TonyLawrence | |||
| - A RAID drive failure slowed the Kerio mailserver to a crawl and eventually brought it down entirely. More than 900 users without mail - what now? - | |||||
| Query Kerio Custom rules | 2012 07 | 2012/07/23 TonyLawrence | |||
| - A script to query Kerio mailserver custom rules or list by type. Partially useful on Windows with Perl or Cygwin. - | |||||
 | |||||
| Fixing excessive user whitelisting | 2012 07 | ||||
| - A beta script for correcting unwanted entries in users Spam whitelist. - | |||||
| Failure of encrypted connection Kerio Mailserver | 2012 07 | 2012/07/20 TonyLawrence | |||
| - An unexpected cause to a failure to receive email from a customer momentarily baffles me. - | |||||
| Kerio Troubleshooting | 2012 05 | ||||
| - There are only a very few things that will completely prevent Kerio Mailserver from starting. Usually this would come from a confused or mangled configuration file, but there are other conditions that can cause Kerio to refuse to start. - | |||||
| Android phone crashes email account | 2012 05 | 2012/05/18 Kanti | |||
| - A misbehaving Android phone caused a user to send duplicate messages - hundreds of them. We stopped that quickly by deleting her account on the phone (it's easy to recreate), but two weeks later her email stopped working - | |||||
| Kerio Control Rip and Replace | 2012 05 | 2013/02/20 TonyLawrence | |||
| - I tore out a perfectly good Astaro Firewall and replaced it with a Kerio Control box. The Astaro was only two years old and was working fine, but tearing it out made both me and my customer very happy. Read on to learn why. - | |||||
| Support is not an annoyance | 2012 05 | 2012/06/01 TonyLawrence | |||
| - Kerio's recent support changes have caused some customer backlash. I am sypathetic to some of these complaints, but I also see the necessity of the change and think it actually can be good for everyone. - | |||||
| Troubleshooting Outlook KOC problems on new Windows 7 machines | 2012 05 | 2012/05/04 TonyLawrence | |||
| - Troubleshooting can lead us down strange paths. Join me as we watch new Windows 7 machines act up after joining a domain. - | |||||
| A Kerio Firewall transplant causes mail problems | 2012 04 | 2012/04/06 TonyLawrence | |||
| - Moving a Kerio Control firewall to new hardware shouldn't be any trouble at all. In fact, it was not, but some red herrings led me to think that something had gone mysteriously wrong. - | |||||
| Troubleshooting a scanner with an email gateway | 2012 03 | 2012/03/28 NickBarron | |||
| - After an email conversion, the only problem was a scanner that could not send email. That should have been a simple fix, but we were led far astray. - | |||||
| Where is the boing? (Mac scheduled startup) | 2012 03 | 2012/04/23 anonymous | |||
| - I first noticed the missing Mac startup chime a few weeks ago. It seemed very odd that if I rebooted, the chime did work - it was only the first boot of the day when it did not "boing". Starting up took too long also - something was wrong, but what? - | |||||
| iPad recovery mode problem caused by bad backup | 2012 03 | 2012/03/12 TonyLawrence | |||
| - When my iPad started crashing Thursday night, it looked like bad hardware. I was even more sure of that when I tried to recover from a backup and it crashed doing that. I took it to the Genius Bar and they agreed, but we all were wrong. - | |||||
| Mysterious Duplicate IP problem solved | 2011 11 | 2011/11/14 NickBarron | |||
| - I only needed to be run over by four or five cluetrains before realizing what was causing this 'IP address conflict' message on a Windows 2003 server. Follow along and see when you solve it. - | |||||
| Local printing in Synchronics | 2011 11 | 2012/03/06 anonymous | |||
| - I know exactly what he has - an old SCO Unix system with a Digiboard multiport serial board, green screen Wyse terminals and Okidata printers with serial cards. I can handle all of that. - | |||||
| Do you hate your computer? | 2011 09 | 2011/09/15 BigDumbDInosaur | |||
| - I knew someone who became so frustrated with a computer printer that he threw it down on the floor and jumped up and down on it until it was smashed to pieces. That's a bit extreme (and damaging to your bank account), but technology can make us feel like that, can't it? - | |||||
| Basic Home Networking, Part 3, File and Printer Sharing | 2011 08 | ||||
| - The point of a computer network is sharing. You might not be sharing much, perhaps even only the Internet connection. If that's the end of it, you don't need much more than part one of this series, which deals with the setup of a basic small network. - | |||||
| Putting the wrong name on a Win 7 user profile | 2011 08 | 2011/08/25 NickBarron | |||
| - However, both of these new computer owners panicked at my suggestion. I explained that they just needed to cable up their new system; they claimed complete inability to do even that. Sigh. Yes, I know that this is mostly in their minds. It's a form of leaned helplessness. If they would just make a small effort, they probably could do this themselves, but they just stop and refuse to even try. It's too complicated, they are afraid that they might damage something or feel foolish. - | |||||
| A few minor iPad set up problems baffle my neighbor | 2011 08 | 2011/08/28 anonymous | |||
| - A neighbor took advantage of MA's recent tax free weekend and bought an iPad. He'd seen mine and his daughter had shown off hers the last time she had visited, so he had a pretty good idea of why he wanted it. Unfortunately, his initial experience was frustrating. - | |||||
| Basic Home Networking - Part 2, wireless setup | 2011 08 | ||||
| - Often all that needs to be done is to tell your computer that you want to connect to a wireless network. It's not always that easy, but it certainly can be. However, even if it is that easy for you, you might still want to read the rest of this in case you have problems later. You also might want to read it because being "too easy" to get connected could mean that you are running some security risk and need to address that issue. - | |||||
| Basic Home Networking - routers and switches | 2011 08 | 2011/08/16 BigDumbDinosaur | |||
| - Setting up a small office or home network used to be a fairly complicated task. Aside from the technical knowledge needed, there was expensive equipment to buy and specialized tools for wiring. That's all changed - the necessary equipment is cheap and readily available and it's all very easy to configu re. - | |||||
| A non-technical guide to understanding and fixing TCP/IP problems on a network | 2011 08 | 2011/08/14 BigDumbDinosaur | |||
| - The title is a bit incorrect in the .non-technical. claim, because we are dealing with a geekish subject here and I can't avoid being a little "techie". - | |||||
| Brother MFC-J615W printer | 2011 08 | ||||
| - I have never been a fan of inkjet printers. In fact. my general advice has been not to buy them because hey are far more expensive to operate than laser printer. These multifunction things have even more to dislike: if you lose part of the functionality, you are going to lose it all while it is out for repair. - | |||||
| Perl Profiling with Devel::NYTProf | 2011 07 | ||||
| - I don't think I have ever used a profiler on my own code. The reasons are simple: I don't write much that is very complicated, so any bottlenecks are usually rather easy to spot. Most of what I do is ad hoc and limited use anyway, so speed is seldom a consideration. - | |||||
| Internet phone service - without the service | 2011 07 | 2011/07/16 BigDumbDinosaur | |||
| - My wife is one who, once on the telephone, can't seem to know when to stop ta lking. Accordingly, our residential phone service bill tends to bear a vague resemblance to the national debt. She can't seem to bring herself to change her phone habits, so I finally caved in against my better judgment and gave her the go-ahead to switch our residential service to voice-over-IP (VoIP). After doing a bit of research, a company called TeleBlend was selected to provision the service. - | |||||
| Mysterious calendar in Kerio Webmail | 2011 07 | ||||
| - Troubleshooting a Kerio calendar: His calendar in Kerio also displays items from M's Google Calendar. This seems straight forward, except neither J or I set this up and both of our users c laim they don't know how it got set up this way. - | |||||
| Why does fsck need a scratch file? | 2011 04 | 2011/06/02 KenPorter | |||
| - Although fsck hasn't needed scratch files for a while, large disks are reopening that need. - | |||||
| Mysterious Duplicate IP addresses | 2011 04 | 2011/04/20 TonyLawrence | |||
| - Proxyarp on smart switch causes sudden appearance of duplicate ip addresses: All machines on our 192.168.206.x subnet (mostly Mac's, with Windows servers) got the IP conflict message when they started up in the morning. We do have a linux dhcp server running on that subnet, but it only hands out 2 IP addresses for barcode guns, and those are given the IP based on their MAC address, so each barcode gun always gets the same IP and can move to other buildings without reconfiguring them, as they run in dhcp mode. - | |||||
| The lowly ls command | 2011 04 | 2011/04/20 TonyLawrence | |||
| - ls might have more flags than any other Unix command and operating system variance is wide. - | |||||
| Three Computer Repair Books | 2011 03 | ||||
| - This is 162 pages, well written, with good humor and full of practical advice for the person starting out on a shoestring. - | |||||
| DUP in ping | 1997-2004 | 2010/09/24 anonymous | |||
| - What causes DUP in ping? Misconfigured or faulty equipment somewhere is likely at fault. - | |||||
| bad block on jaz drive -->Re Using fsdb on damagedfilesystems | 1997-2004 | ||||
| - Using fsrd to repair damaged filesystems - | |||||
| Dealing with Duplicate IP addresses | 2009 04 | 2011/11/13 TonyLawrence | |||
| - Duplicate IP's on a network is an interesting problem that has no completely satisfactory solution, especially when malicious intent is involved. Let's leave those intentional conditions for another day; here we'll look at what happens when an IP gets duped accidentally. - | |||||
| A Golf Cart is not a Computer | 2008 05 | 2013/03/05 TonyLawrence | |||
| - You can't let batteries discharge over the winter, so when it got cold I moved it out back near an electrical outlet where I could plug the charger in. - | |||||
| RTL8111/8168B PCI Express Gigabit Ethernet Failure | 2008 12 | 2011/10/16 anonymous | |||
| - Forcing driver with Realtek RTL8111 - an "lspci -vv" revealed that things were not right.. - | |||||
| General Trouble Shooting | 2000 08 | 2010/12/24 anonymous | |||
| - Sometimes computer problems can feel like Dickens' dying woman- you know something is wrong, but you have no idea where or how to start looking for it. - | |||||
| Invalidating the Linux buffer cache | 2006 12 | 2012/08/01 SimonL | |||
| - How to actually test the disk drive to know that data really has gotten to the disk drive. This could be because you want to test the performance of the drive, but could also be when you suspect a drive is malfunctioning: if you just write and read back, you'll be reading from cache, not from actual disk platters. - | |||||
| Maximun number of socket connections | 2006 02 | ||||
| - 100 connections hangs server.. configuration? Possible tuning limits on SCO Unix that might cause this. - | |||||
| Network Troubleshooting | 2010 03 | 2010/03/16 AndrewSmallshaw | |||
| - As it turned out, the problem was very physical: a light fixture had fallen down and loosened some connections to a long forgotten ethernet switch. - | |||||
| opensnoop (Mac file open watcher) | 2007 12 | ||||
| - opensnoop is powerful stuff, but it's easy to misuse. There is a large pile of pre-made Dtrace scripts available on Mac OS X Leopard. - | |||||
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| corrupt header This does not look like a tar archive skipping to next header archive contains obsolescent base-64 headers | 1997-2004 | ||||
| - Perl script can fix some corrupt tar archives - | |||||
| timeout of ping -->Re timeout of ping | 1997-2004 | ||||
| - The new flag, carped from BSD, means 'stop the whole ping session after this much time, regardless of how many packets have been sent or received, or current success status'. - | |||||
| I see in netstat that processes get stuck in TIME_WAIT | 1997-2003 | ||||
| - For some reason, OpenServer sets TIME_WAIT to 30 minutes even while stating that the recommended setting is 4 minutes! - | |||||
| excluding files from rsync --exclude | 1997-2004 | ||||
| - Trying to exclude files from rsync can be very confusing. Testing with local files or small data sets can help. There are some gotchas to watch out for, though. - | |||||
| Geek Wiring | 2006 06 | ||||
| - Our phones went dead yesterday. Unfortunately, that's becoming a common occurrence, and it has caused us to be very ticked off at Comcast because we've been without service a lot. - | |||||
| Troubleshooting network connections with arp | 2003 08 | ||||
| - Identifying systems by mac address. MAC address ranges are assigned by the IEEE to electronics manufacturers to ensure that MAC addresses are globally unique. - | |||||
| gunzip File Size Limit Exceeded (core dumped) | 1997-2004 | ||||
| - The size of an individual file is limited to 2GB in OpenServer. Presumably you mean that the unzipped size is ~5GB and the zipped size is smaller? The amount of data that can flow through a pipe is not limited to 2GB. (But it will still fail if any individual file stored in the tar archive is larger than 2GB.) - | |||||
| C Pointer Problems | 2005 07 | 2011/04/18 TonyLawrence | |||
| - If a program works under a debugger but crashes otherwise, the problem is almost always an uninitialized pointer. - | |||||
| mail carriage return newlines -->Re CarriageReturns???? | 1997-2004 | ||||
| - mail carriage return newlines -->Re: CarriageReturns???? - | |||||
