A special extended edition of Tech Messages for 2011-09-21 through 2012-05-11:

• Understanding Linux CPU Load - when should you be worried?
• Performance Testing - Load Balancer SSL Stress Testing
  This is a great simple test. Thanks, Corey!
• Mosh: the mobile shell
• Twitter open sources its MySQL secret sauce
• Lab Overview
  This guy is serious about his lab!

A special extended edition of Tech Messages for 2011-08-31 through 2011-09-21:

• Lab Overview
  This guy is serious about his lab!
• Throughput
  All sorts of useful information here. My favorite is the first table which includes bandwidth and packet throughput for different kids of circuits.
• Must see: 5 Steps to Scaling MongoDB (Or Any DB) in 8 Minutes
  These tips are relevant no matter what database system you are using.

A special extended edition of Tech Messages for 2011-01-12 through 2011-01-15:

• Hg Init: a Mercurial tutorial by Joel Spolsky
  An introduction to Mercurial (hg) by Joel Spolsky. Includes a special introductory chapter for Subversion users.
• lessfs | Open source data de-duplication
  Open source filesystem with de-duplication.
• UCS B-Series and C-Series Servers Log Memory Errors due to Intel 5600 Erratum Issue
  On a subset of Intel Xeon 5600 series processors, during packet C6 transitions, CPU circuit marginality or internal signaling noise in the may lead to an invalid memory DRAM state, system hang,
  

A special extended edition of Tech Messages for 2010-12-22 through 2011-01-04:

• WS-C3560V2-XXXX-X, WS-C3750V2-XXXX-X Series RPS cover and rare power reset – Replacement Recommended
  The RPS cover for wall-mount of the Acc Kits in the BOM was not correct; it should be 22P instead of 14P. The issue is a safety issue for those who choose to wall-mount the RPS. It's found on WK48P/NZ48P that the magjack connector's shielding were short to the test via 2.5v to ground. Adding capton tape underneath Belfuse/Pulse connector to avoid the short via ECO as a short term solution will respin PWB to correct issue.
• WordPress › 3.0.4

A special extended edition of Tech Messages for 2010-12-14 through 2010-12-21:

• Cisco IOS Hints and Tricks: IOS HTTP client sets Host: field to IP address
  Still annoying…
• ACL IP Options Selective Drop – Cisco Systems
  Most networks do not make use of IP options. You can drop packets that contain options with the "ip option drop" global configuration command.
• Which loads faster?
  This tool has it's usefulness. It's especially nice to compare your site to similar sites and see what you can do to improve
  

In a test lab, we ran into a situation where the connection between our Cisco Access Registrar (AAA) server and MySQL server was timing out. This forced the server to reconnect and resulted in the following errors:

 name/radius/1 Error Server 0 ODBC client (DataSource 'my_odbc', Connection 8): SQLExecute failed: SQLState:08S01 NativeError:2006 ErrorText:[MySQL][ODBC 3.51 Driver][mysqld-5.0.21-log] MySQL server has gone away
name/radius/1 Error Server 0 Service odbc has no active remote servers available

Obviously, the MySQL server was still there, but after the wait_timeout expires, the server severs the idle connections. By default, the wait_timeout is set to 8 hours. This is obviously much longer than is usually necessary, but in our test lab, it caused problems every morning.

The fix is

I have just returned from holiday and while it’s not normal reading during some of my spare time I managed to read a couple of books on IPv6 I’d recently bought to get me up to scratch and refresh my memory on the topic.

These books are:

• Deploying IPv6 Networks, by Cisco
• Understanding IPv6, Second Edition by Microsoft

The first book is quite good, and while a little old provided a good solid background for me on the subject. A lot of the information was not relevant to my interest in setting up a networked SOHO network but that’s not really a problem. The background was interesting.

The second book was a bit of a mistake.

A special extended edition of Tech Messages for 2010-04-29 through 2010-05-14:

• PowerDNS
  DNS server supporting a variety of backends including BIND-style configuration files and relational databases. Also supports providing different answers based on a requester's geographic location.
• Updated - UMPIRE Archived -- ESR or uBR PRE2 Unable To Read PCMCIA ATA Flash Disk - Data Loss or System Boot Hang - Replace Flash Card
  The PCMCIA ATA Flash Disks used in specific Cisco products may contain a Manufacturing defect which reduces reliability of the Flash device. PRE2 cards used both in the Cisco ESR10000 and uBR10000 platforms
  

A special extended edition of Tech Messages for 2010-02-20 through 2010-02-24:

• Gartner EXP Worldwide Survey of Nearly 1,600 CIOs Shows IT Budgets in 2010 to be at 2005 Levels
  Virtualization tops the technology priorities.
• Cisco Offers Three-Year, Zero-Percent Financing to U.S. Small and Medium-Sized Businesses -> Cisco News
• Marc Alff's blog: Performance schema overview
  Really interesting stuff for MySQL developers.

I track security updates for the following vendors: Apple, Cisco, FreeBSD, Microsoft, Red Hat, and Sun Microsystems. I chose these vendors based on my own needs for the networks and systems I manage. I've also found that updates from these vendors tend to catch the major updates necessary for common software applications. If you have other vendors you would like me to provide updates for, send me a message.

If you have an interest in information security from both a technical and managerial level, check out Principles of Information Security. It does an excellent job of presenting material for both audiences.

Cisco Systems Inc.

A special extended edition of Tech Messages for 2009-06-16 through 2009-06-25:

• MySQL – Restoring a Single Table from a Huge mysqldump File
  This is is hugely helpful if you don't want to restore a 25GB dump file just to grab one table.
• MCS-7828-H3: Hard Drive Errors Cause Service Outage; Hard Drive Firmware Upgrade Required
  Certain Seagate hard drive models used in HP servers (listed in the Products Affected section of this document) that are configured with firmware versions prior to HPG6 might experience drive failure indications.