The Basics of Network Troubleshooting

The following post is something I wrote as an in-house primer for our help desk staff. While it a bit down level from a lot of the content here I find more and more the picking and reliably going with a troubleshooting methodology is somewhat of a lost art. If you are just getting started in networking or are troubleshooting connectivity issues at your home or SMB this would be a great place to start.

We often get issues which are reported as application issues but end up being network related. There are a number steps and logical thought processes that can make dealing with even the most difficult network issues easy to troubleshoot. The purpose of this post is to outline many of the basic steps of troubleshooting network issues, past that it’s time to reach out and ask for assistance.

  • Understand the basics of OSI model based troubleshooting

    The conceptual idea of how a network operates within a single node (computer, smartphone, printer, etc.) is defined by something called the OSI reference model. The OSI model breaks down the operations of a network into 7 layers, each of which is reliant on success at the layers below it (inbound traffic) and above it (outbound traffic). The layers (with some corresponding protocols you’ll recognize) are:

    7. Application: app needs to send/receive something (HTTP, HTTPS, FTP, anything that the user touches and begins/ends network transmission)
    6. Presentation: formatting & encryption (VPN and DNS host names)
    5. Session: interhost communication (nothing to see here:))
    4. Transport: end to end negotiations, reliability (the age old TCP vs. UDP debate)
    3. Network: path and logical addressing (IP addresses & routing)
    2. Data Link: physical addressing (MAC addresses & switches)
    Go Read More

  • Vegas Baby! Heading to CiscoLive! 2016

    As 2016 moves into April we find ourselves ready to go into the conference season once again. For the past couple of years I’ve been to VMworld because that is where my work has had me focused, but for the same reason I will be heading the Cisco Live in Las Vegas, NV this year. The event will be held at the Mandalay Bay Resort July 10-14. Yes it will be hot, but let’s be honest you are going to be inside most of the time. This is the 2nd time I’ve attended Cisco Live US (you may see it referred to as #CLUS quite a bit) and if this is anything like the last time it’s going to be great. I have been particularly impressed with the content they make available and the community that has grown around it.

    What to do

    The first and foremost thing you should check out at Cisco Live is the always excellent sessions throughout the conference. If you are new to conferences this is actually something to consider sooner than later; the session catalog is currently up and the scheduler will open on May 3. I recommend that if you have any particular sessions or focus you are looking at with this trip go ahead and have a list done early and then be ready on the 5/3, many popular sessions will fill up quickly and nobody wants to wait in the overflow line. 😉

    To be honest if you just look at the scope of topics covered in the session list it is a bit overwhelming. While I’m no grizzled veteran of conferences by any means what I’ve found best is to pick a focus or two and then start there. For example this year we have a big focus on … Go Read More

    Quieting the LogPartitionLowWaterMarkExceeded Beast in Cisco IPT 9.0.x Products

    As a SysAdmin I’m used to waking up, grabbing my phone and seeing the 20 or so e-mails that  the various systems and such have sent me over night, gives me an idea of how the day will go and what I need start with. Every so often though you get that morning where the 20 becomes 200 and you just want to roll over and go back to bed. This morning I had about 200, the vast majority of which was from my Cisco Unified Contact Center Express server with the subject “LogPartitionLowWaterMarkExceeded.” Luckily I’ve had this before and know what to do with it but on the chance you are getting it too here’s what it means and how to deal with it in an efficient manner.

    WTF Is This?!?

    Or at least that was my response the first time I ran into this. If you are a good little voice administrator one of the first things you do when installing your phone system or taking one over due to job change is setup the automatic alerting capability in the Cisco Unified Real Time Monitoring Tool (or RTMT, you did install that, right?) so that when things go awry you know in theory before the users do. One of the downsides to this system is it is an either on or off alerting system meaning what ever log events are saved within the system are automatically e-mailed at the same frequency.

    This particular error message is the by-product of a bug (CSCul18667) in the 9.0.x releases of all the Cisco IP Telephony products in which the JMX logs produced by the at the time new Unified Intelligence Center didn’t get automatically deleted to maintain space on the log partition. While this has long since been fixed phone systems are … Go Read More

    Updating the Photo Attributes in Active Directory with Powershell

    Today I got to have the joys of needed to once again get caught up on importing employee photos into the Active Directory photo attributes, thumbnailPhoto and jpegPhoto. While this isn’t exactly the most necessary thing on Earth it does make working in a Windows environment “pretty” as these images are used by things such as Outlook, Lync and Cisco Jabber among other. In the past the only way I’ve only ever known how to do this is by using the AD Photo Edit Free utility, which while nice tends to be a bit buggy and it requires lots of repetitive action as you manually update each user for each attribute. This year I’ve given myself the goal of 1) finally learning Powershell/PowerCLI to at least the level of mild proficiency and 2) automating as many tasks like this as possible. While I’ve been dutifully working my way through a playlist of great PluralSight courses on the subject, I’ve had to live dangerously a few times to accomplish tasks like this along the way.

    So long story short with some help along the way from Googling things I’ve managed to put together a script to do the following.

  • Look in a directory passed to the script via the jpgdir parameter for any images with the file name format <username>.jpg
  • Do an Active Directory search in an OU specified in the ou parameter for the username included in the image name. This parameter needs to be the full DN path (ex. LDAP://ou=staff,dc=foo,dc=com)
  • If the user is found then it will make a resized copy of the image file into the “resized” subdirectory to keep the file sizes small
  • Finally the resized image is then set as the both the thumbnailPhoto and jpegPhoto attribute for the user’s AD account
  • So your basic … Go Read More

    A how-to on cold calling from the customer perspective

    Now that I’m back from my second tech conference in less than two months I am fully into the cold call season and I am once again reminded why I keep meaning to buy a burner phone and setup a Gmail account before I register next year. It seems every time I get back I am destined to months of “I am so glad you expressed deep interest in our product and I’d love to tell you more about it” when the reality is “I am calling you because you weren’t nimble enough to lunge away from our team of booth people who are paid or retained based on as many scans they can get. Most often when I get these calls or e-mails I’ll give each company a courteous thanks but no thanks and after that the iDivert button gets worn out.

    The genesis of this post is two-fold. First a cold call this morning that was actually destined for my boss but when informed he wasn’t here went into telling how glad the person was that I had personally expressed interest in their product, WTF? This first event reminded me of a second, where a few months ago I was at a mixer preceding a vendor supplied training when I was approached by a bevy of 20 something Inside Sales Engineers and asked “what can I do to actually get you to listen?” From this I thought that just in case a young Padawan Sales Rep/Engineer happens to come across this, here are those ways to make your job more efficient and to stop alienating your potential customers.

    Google Voice is the Devil

    I guess the first step for anybody on the calling end of a cold call scenario is to get me to answer the phone. My … Go Read More

    Veeam Backup Repository Best Practices Session Notes

    After a couple days off I’m back to some promised VeeamON content. A nice problem that VeeamON had this year is the session choices were much more diverse and there were a lot more of them. Unfortunately this led to some overlap of some really great sessions. A friend of mine, Jaison Bailey of vBrisket fame and fortune, got tied up in another session and was unable to attend what I considered one of the best breakout sessions all week, Anton Gostev‘s Backup Repository Best Practices so he asked me to post my notes.

    For those not too familiar with Veeam repos they can essentially be any manner of addressable disk space, whether local, DAS, NAS, SAN or even cloud, but when you start taking performance into account you have to get much more specific. Gostev, who is the Product Manager for Backup & Replication, lines out the way to do it right.

    Anyway, here’s the notes including links to information when possible. Any notations I have are in bold and italicized.

    Don’t underestimate the importance of Performance

    • Performance issues may impact RTOs

    Five Factors of choosing Storage

    • Reliability
    • Fast backups
    • Fast restores
    • DR from complete storage loss
    • Lowest Cost

    Ultimate backup Architecture

    • Fast, reliable primary storage for fastest backups, then backup copy to Secondary storage both onsite AND offsite
    • Limit number of RP on primary, leverage cheap secondary
    • Selectively create offsite copies to tape, dr site, or cloud

    Best Repo: Low End

    • Any Windows or Linux Server
      • Can also serve as backup /backup proxy server
    • Physical server storage options
      • Local Storage
      • DAS (JBOD)
      • SAN LUN
    • Virtual
      • iSCSI LUN connected to in guest Volume

    Best Backup Repo: High End

    Getting Started with rConfig on CentOS 7

    I’ve been a long time user of RANCID for change management on network devices but frankly it’s always left me feeling a little bit of a pain to use and not particularly modern. I recently decided it was time for my OpenNMS/RANCID server to be rebuilt, moving OpenNMS up to a CentOS 7 installation and in doing so thought it was time to start looking around for an network device configuration management alternative. As is many times the way in the SMB space, this isn’t a task that actual budgetary dollars are going to go towards so off to Open Source land I went!  rConfig immediately caught my eye, looking to me like RANCID’s hipper, younger brother what with its built in web GUI (through which you can actually add your devices), scheduled tasks that don’t require you to manually edit cron, etc. The fact that rConfig specifically targets CentOS as its underlaying OS was just a whole other layer of awesomesauce on top of everything else.

    While rConfig’s website has a couple of really nice guides once you create a site login and use it, much to my dismay I found that they hadn’t been updated for CentOS 7 and while working through them I found that there are actually some pretty significant differences that effect the setup of rConfig. Some difference of minor (no more iptables, it’s firewalld) but it seems httpd has had a bit of an overhaul. Luckily I was not walking the virgin trail and through some trial, error and most importantly google I’ve now got my system up and running. In this post I’m going to walk through the process of setting up rConfig on a CentOS minimal install with network connectivity with hopes that 1) it may help you, the two … Go Read More

    Community and the Rural IT Professional

    I was born and raised in a small area between Charleston and Huntington, WV. While I recognized my hometown, Scott Depot, was a small town growing up I thought of both those cities as just that, proper cities with all the benefits and drawbacks that go with them. As I grew older and my worldly view wider I came to realize that what I considered the big city was to many a minor suburb, but never the less it was and still is my home.

    This lack of size and economic opportunity has never stood out more than when I began my career in Information Technology. After graduating from Marshall University with what I still believe to be a very respectable skill set many of my fellow graduates flocked to bigger areas such as Columbus, OH, RTP and Atlanta. I chose for a variety of reasons to stick around here and make a career of it and all in all while not always the most stable it has been fairly successful.

    There are very few large datacenters here with most datacenters being composed of a handful of racks. Some go to work for various service providers, others enter the VAR space and I found my niche in what I like to call the Hyper Converged Administrator role. The HCA tends to wear most if not all of the hats; virtualization, storage, networking, server administration, etc. I consider myself somewhat blessed that I’ve managed to avoid the actual desktop admin stuff for most of my career, but still some of that too.

    In the past couple of years I’ve got more and more active within the social IT community by way of conference attendance, social media and blogging and while it hasn’t necessarily changed the direction my career is going … Go Read More

    Presenting at VeeamON 2015: Design, Manage and Test Your Data Protection with Veeam Availabilty Suite

    Last week I was presented with the honor of being invited to speak at Veeam Software‘s annual user conference, VeeamON. While this was not my first time doing so I was very happy with the end result this year, with 30-40 attendees and positive feedback both from people I knew beforehand as well as new acquaintances who attended.

    My session is what I like to think of as the 1-1000 MPH with Veeam, specifically targeting the SMB space but with lots of general guidelines for how to get your DR system up and running fast and as error-free as possible. Some of the things I do with Veeam buck the Best Practices guide but we have been able to maintain high levels of protection over many years without much interruption. The session starts with the basics of designing your DR plan, then designing your Veeam infrastructure components to suit your needs, followed by tips for the actual implementation and other tricks and gotchas I’ve run into over the years.

    Anyway due to the amount of information that was covered I promised attendee’s that I would put my slide deck out here for reference so here it is. If anybody has comments, questions or anything in between please feel free to reach out to me either through the comments here or on twitter. For attendees please keep an eye on your e-mail and the #VeeamON hashtag as the videos of all presentations should be made available in the coming weeks.
    This is an embedded Microsoft Office presentation, powered by Office Online.

    Let’s See How This Goes: Getting Started with vDM30in30

    For those of you that don’t know the idea of #vDM30in30 (virtual Design Master: 30 articles in 30 days) started last year by the same fine folks that bring you vDM with the stated goal of getting people to write more and become better writers. You can learn more about the basic rules in Eric Wright’s (aka discoposse) post announcing this year’s event. I caught up to the idea a little late in the game to make any kind of effort at it, but this year due to my writer’s funk of late I’ve decided to give it a go.

    So what do I expect to write about? Since I’m freshly back from Veeam Software‘s annual VeeamON conference expect quite a bit of content related to that. Also I’ve had a few ideas regarding career and community here lately so there will be quite a bit of that as well. Past that? I guess we’ll just have to see what happens.

    If you are interested in participating yourself really the only two things you need to remember is to write/create content anywhere (go setup a blogger.com account if you don’t have a site yet) and then post to social media with the #vDM30in30 hashtag, that’s it! If you don’t feel like you are ready for that kind of commitment, trust me, I get you, then you can still follow along and learn from everybody else using the same hashtag. For those of you who are participating good job and I look forward to learning from you!