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  • What switch should we use for PCoIP?

    - by Jay R.
    We have a small lab space that seats 10 people and has 20 machines. Each machine is set to 1920x1200 resolution because the user apps are best used at that resolution. Currently the machines are all located close enough to montors that a DisplayPort cable will reach, but the pending lab remodel positions them around 80 feet or more away in racks. Our proposed solution is to use PCoIP. We purchased 10 PCoIP portals and 20 PCoIP host cards. We plan to set up a dedicated network to handle just the PCoIP traffic. After testing just one portal and one host card with a cheap 1G switch from a local office supply store, we were left with less than good impressions about the usefulness in our lab. The framerates were not spectacular and the mouse seemed jerky. Our concern is that we can't get away with the cheap 1G stuff from the store because adding more machines to the switch will just make the user experience worse. What switch would be recommended to best support our PCoIP situation? We will need to plug in at least 30 cables based on just those machines. Is there a particular feature to search for that makes a difference? Is there a switch that works best with PCoIP? Added Info: The reporting webapp for the host card shows maximum bandwidth usage to be 220000 kbps. The average appears to be around 180000 kbps. The reverse direction is much lower, like 15000 kbps.

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  • Linux Distro - GUI similar to Windows

    - by DeaconDesperado
    I am in the process of refurbing several older laptop machines for use by a couple college guys we have in training to learn basic web development in python. These are students who intern at my company and are hoping to do some work when the summer comes building simple client-oriented webapps (learning the basics of OOP, MVC webapp design in flask, etc.). We're trying to function as the "practical" side of their education. I would like to get them set up on these machines we have sitting about, but I'd like to use a linux distro that would have a gui that closely approximates what they are being compelled to use at school (windows.) I don't really have much of a preference as far as GUI goes since much of what we'll be learning together is accomplished on the command line. I just see this as an easier adjustment for them while they are still reliant on a graphical environment. In the past I'd go straight for Ubuntu, but since they started using the Unity GUI the responsiveness overall can be pretty clunky on older machines, especially since these machines (there are four of them) run the gambit on specs (though all are at least 1.0Ghz and none have anything better than basic integrated video.) Has anyone had to setup a similar working environment in Mint, bare Debian or Zorin? Thanks.

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  • Linux iptables / conntrack performance issue

    - by tim
    I have a test-setup in the lab with 4 machines: 2 old P4 machines (t1, t2) 1 Xeon 5420 DP 2.5 GHz 8 GB RAM (t3) Intel e1000 1 Xeon 5420 DP 2.5 GHz 8 GB RAM (t4) Intel e1000 to test linux firewall performance since we got bitten by a number of syn-flood attacks in the last months. All machines run Ubuntu 12.04 64bit. t1, t2, t3 are interconnected through an 1GB/s switch, t4 is connected to t3 via an extra interface. So t3 simulates the firewall, t4 is the target, t1,t2 play the attackers generating a packetstorm thorugh (192.168.4.199 is t4): hping3 -I eth1 --rand-source --syn --flood 192.168.4.199 -p 80 t4 drops all incoming packets to avoid confusion with gateways, performance issues of t4 etc. I watch the packet stats in iptraf. I have configured the firewall (t3) as follows: stock 3.2.0-31-generic #50-Ubuntu SMP kernel rhash_entries=33554432 as kernel parameter sysctl as follows: net.ipv4.ip_forward = 1 net.ipv4.route.gc_elasticity = 2 net.ipv4.route.gc_timeout = 1 net.ipv4.route.gc_interval = 5 net.ipv4.route.gc_min_interval_ms = 500 net.ipv4.route.gc_thresh = 2000000 net.ipv4.route.max_size = 20000000 (I have tweaked a lot to keep t3 running when t1+t2 are sending as many packets as possible). The result of this efforts are somewhat odd: t1+t2 manage to send each about 200k packets/s. t4 in the best case sees aroung 200k in total so half of the packets are lost. t3 is nearly unusable on console though packets are flowing through it (high numbers of soft-irqs) the route cache garbage collector is no way near to being predictable and in the default setting overwhelmed by very few packets/s (<50k packets/s) activating stateful iptables rules makes the packet rate arriving on t4 drop to around 100k packets/s, efectively losing more than 75% of the packets And this - here is my main concern - with two old P4 machines sending as many packets as they can - which means nearly everyone on the net should be capable of this. So here goes my question: Did I overlook some importand point in the config or in my test setup? Are there any alternatives for building firewall system especially on smp systems?

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  • Can only ssh when not using wifi

    - by AChrapko
    So I have 3 machines, a windows 7 desktop that is always wired to my router, osX laptop, and raspberry pi running debian linux. My router is a Linksys e1000 wireless N. My goal is to be able to ssh the raspi from any machine, while it is connected via wifi. My problem is that when trying to ssh from either the win7 or osX to the Pi it either times out, or gives an error: "ssh: connect to host 192.168.1.### port 22: No route to host" The only times that I have managed to connect to the pi from any machine were when it connected to the router via an Ethernet cable. Currently with win7 desktop wired, macbook wireless, and pi wireless tests give the following: win7 ping macbook: Destination host unreachable. macbook ping win7: Request timeout. win7 ping pi: Destination host unreachable. macbook ping pi: Request timeout. blah blah blah Plugging the macbook into the router with an Ethernet cable all communication between win7 and macbook works. Pings, ssh, ftp, smb ect... No changes to the pi, still no connections possible to or from any of the other 2 machines. Note All machines, are able to connect to the internet and ssh to the same machine on a completely different network, wired or over wifi. Plugging the Pi in with Ethernet (and macbook still wired) I can ssh to the pi from both win7 and macbook. I can ssh from the pi to macbook. All machines still able to connect the the off network machine. Also another little side note- I was playing warcraft 3 with my roommates the other day, and the only time they were able to see my LAN game was when they were plugged into the router with an Ethernet cable. Once or twice one of the laptops was able to connect over wifi, but not without another computer connecting first via Ethernet. So basically does anyone have any info as to why my router seems to completely ignore local wireless traffic?

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  • VMware ESX Linux Guest Customization

    - by andyh_ky
    Hello, I am interested in deploying several RHEL 4 Update 8 virtual machines for creation of a test environment. Here are the steps I am taking: In off hours, P2V/V2V the production machines and convert them to templates Deploy the virtual machines with a customization specification that changes hostname, IP address I am interested in how these processes are done and if there are any options for further customization. Are the machines brought on the network when they are powered on, before they are reconfigured? Is there a potential IP address conflict? Is there an option to run additional scripts which reside on the guest as a part of the reconfiguration? For example, restoring an Oracle Database. This is an option with Windows guests and sysprep, but I have been unable to locate anything showing a RHEL equivalent. I am dealing with a multi tier application. The main issue I am attempting to mitigate is that the application servers reference database servers by hostname and in tnsnames files. I am interested in scripting the reconfiguration of the application in the deployment so that the app/db servers are pointing to the test environment. I am OK with placing the 'cleanup' script on the source and executing it after the machine has been brought up. I am interested in the automation of the script's execution post clone/boot, as well as if there could be an IP address conflict. (cross posted to VMTN's ESX 4 community)

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  • Using Deployment Manager

    - by Jess Nickson
    One of the teams at Red Gate has been working very hard on a new product: Deployment Manager. Deployment Manager is a free tool that lets you deploy updates to .NET apps, services and databases through a central dashboard. Deployment Manager has been out for a while, but I must admit that even though I work in the same building, until now I hadn’t even looked at it. My job at Red Gate is to develop and maintain some of our community sites, which involves carrying out regular deployments. One of the projects I have to deploy on a fairly regular basis requires me to send my changes to our build server, TeamCity. The output is a Zip file of the build. I then have to go and find this file, copy it across to the staging machine, extract it, and copy some of the sub-folders to other places. In order to keep track of what builds are running, I need to rename the folders accordingly. However, even after all that, I still need to go and update the site and its applications in IIS to point at these new builds. Oh, and then, I have to repeat the process when I deploy on production. Did I mention the multiple configuration files that then need updating as well? Manually? The whole process can take well over half an hour. I’m ready to try out a new process. Deployment Manager is designed to massively simplify the deployment processes from what could be lots of manual copying of files, managing of configuration files, and database upgrades down to a few clicks. It’s a big promise, but I decided to try out this new tool on one of the smaller ASP.NET sites at Red Gate, Format SQL (the result of a Red Gate Down Tools week). I wanted to add some new functionality, but given it was a new site with no set way of doing things, I was reluctant to have to manually copy files around servers. I decided to use this opportunity as a chance to set the site up on Deployment Manager and check out its functionality. What follows is a guide on how to get set up with Deployment Manager, a brief overview of its features, and what I thought of the experience. To follow along with the instructions that follow, you’ll first need to download Deployment Manager from Red Gate. It has a free ‘Starter Edition’ which allows you to create up to 5 projects and agents (machines you deploy to), so it’s really easy to get up and running with a fully-featured version. The Initial Set Up After installing the product and setting it up using the administration tool it provides, I launched Deployment Manager by going to the URL and port I had set it to run on. This loads up the main dashboard. The dashboard does a good job of guiding me through the process of getting started, beginning with a prompt to create some environments. 1. Setting up Environments The dashboard informed me that I needed to add new ‘Environments’, which are essentially ways of grouping the machines you want to deploy to. The environments that get added will show up on the main dashboard. I set up two such environments for this project: ‘staging’ and ‘live’.   2. Add Target Machines Once I had created the environments, I was ready to add ‘target machine’s to them, which are the actual machines that the deployment will occur on.   To enable me to deploy to a new machine, I needed to download and install an Agent on it. The ‘Add target machine’ form on the ‘Environments’ page helpfully provides a link for downloading an Agent.   Once the agent has been installed, it is just a case of copying the server key to the agent, and the agent key to the server, to link them up.   3. Run Health Check If, after adding your new target machine, the ‘Status’ flags an error, it is possible that the Agent and Server keys have not been entered correctly on both Deployment Manager and the Agent service.     You can ‘Check Health’, which will give you more information on any issues. It is probably worth running this regardless of what status the ‘Environments’ dashboard is claiming, just to be on the safe side.     4. Add Projects Going back to the main Dashboard tab at this point, I found that it was telling me that I needed to set up a new project.   I clicked the ‘project’ link to get started, gave my new project a name and clicked ‘Create’. I was then redirected to the ‘Steps’ page for the project under the Projects tab.   5. Package Steps The ‘Steps’ page was fairly empty when it first loaded.   Adding a ‘step’ allowed me to specify what packages I wanted to grab for the deployment. This part requires a NuGet package feed to be set up, which is where Deployment Manager will look for the packages. At Red Gate, we already have one set up, so I just needed to tell Deployment Manager about it. Don’t worry; there is a nice guide included on how to go about doing all of this on the ‘Package Feeds’ page in ‘Settings’, if you need any help with setting these bits up.    At Red Gate we use a build server, TeamCity, which is capable of publishing built projects to the NuGet feed we use. This makes the workflow for Format SQL relatively simple: when I commit a change to the project, the build server is configured to grab those changes, build the project, and spit out a new NuGet package to the Red Gate NuGet package feed. My ‘package step’, therefore, is set up to look for this package on our feed. The final part of package step was simply specifying which machines from what environments I wanted to be able to deploy the project to.     Format SQL Now the main Dashboard showed my new project and environment in a rather empty looking grid. Clicking on my project presented me with a nice little message telling me that I am now ready to create my first release!   Create a release Next I clicked on the ‘Create release’ button in the Projects tab. If your feeds and package step(s) were set up correctly, then Deployment Manager will automatically grab the latest version of the NuGet package that you want to deploy. As you can see here, it was able to pick up the latest build for Format SQL and all I needed to do was enter a version number and description of the release.   As you can see underneath ‘Version number’, it keeps track of what version the previous release was given. Clicking ‘Create’ created the release and redirected me to a summary of it where I could check the details before deploying.   I clicked ‘Deploy this release’ and chose the environment I wanted to deploy to and…that’s it. Deployment Manager went off and deployed it for me.   Once I clicked ‘Deploy release’, Deployment Manager started to automatically update and provide continuing feedback about the process. If any errors do arise, then I can expand the results to see where it went wrong. That’s it, I’m done! Keep in mind, if you hit errors with the deployment itself then it is possible to view the log output to try and determine where these occurred. You can keep expanding the logs to narrow down the problem. The screenshot below is not from my Format SQL deployment, but I thought I’d post one to demonstrate the logging output available. Features One of the best bits of Deployment Manager for me is the ability to very, very easily deploy the same release to multiple machines. Deploying this same release to production was just a case of selecting the deployment and choosing the ‘live’ environment as the place to deploy to. Following on from this is the fact that, as Deployment Manager keeps track of all of your releases, it is extremely easy to roll back to a previous release if anything goes pear-shaped! You can view all your previous releases and select one to re-deploy. I needed this feature more than once when differences in my production and staging machines lead to some odd behavior.     Another option is to use the TeamCity integration available. This enables you to set Deployment Manager up so that it will automatically create releases and deploy these to an environment directly from TeamCity, meaning that you can always see the latest version up and running without having to do anything. Machine Specific Deployments ‘What about custom configuration files?’ I hear you shout. Certainly, it was one of my concerns. Our setup on the staging machine is not in line with that on production. What this means is that, should we deploy the same configuration to both, one of them is going to break. Thankfully, it turns out that Deployment Manager can deal with this. Given I had environments ‘staging’ and ‘live’, and that staging used the project’s web.config file, while production (‘live’) required the config file to undergo some transformations, I simply added a web.live.config file in the project, so that it would be included as part of the NuGet package. In this file, I wrote the XML document transformations I needed and Deployment Manager took care of the rest. Another option is to set up ‘variables’ for your project, which allow you to specify key-value pairs for your configuration file, and which environment to apply them to. You’ll find Variables as a full left-hand submenu within the ‘Projects’ tab. These features will definitely be of interest if you have a large number of environments! There are still many other features that I didn’t get a chance to play around with like running PowerShell scripts for more personalised deployments. Maybe next time! Also, let’s not forget that my use case in this article is a very simple one – deploying a single package. I don’t believe that all projects will be equally as simple, but I already appreciate how much easier Deployment Manager could make my life. I look forward to the possibility of moving our other sites over to Deployment Manager in the near future.   Conclusion In this article I have described the steps involved in setting up and configuring an instance of Deployment Manager, creating a new automated deployment process, and using this to actually carry out a deployment. I’ve tried to mention some of the features I found particularly useful, such as error logging, easy release management allowing you to deploy the same release multiple times, and configuration file transformations. If I had to point out one issue, then it would be that the releases are immutable, which from a development point of view makes sense. However, this causes confusion where I have to create a new release to deploy to a newly set up environment – I cannot simply deploy an old release onto a new environment, the whole release needs to be recreated. I really liked how easy it was to get going with the product. Setting up Format SQL and making a first deployment took very little time. Especially when you compare it to how long it takes me to manually deploy the other site, as I described earlier. I liked how it let me know what I needed to do next, with little messages flagging up that I needed to ‘create environments’ or ‘add some deployment steps’ before I could continue. I found the dashboard incredibly convenient. As the number of projects and environments increase, it might become awkward to try and search them and find out what state they are in. Instead, the dashboard handily keeps track of the latest deployments of each project and lets you know what version is running on each of the environments, and when that deployment occurred. Finally, do you remember my complaint about having to rename folders so that I could keep track of what build they came from? This is yet another thing that Deployment Manager takes care of for you. Each release is put into its own directory, which takes the name of whatever version number that release has, though these can be customised if necessary. If you’d like to take a look at Deployment Manager for yourself, then you can download it here.

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  • Complete Guide to Networking Windows 7 with XP and Vista

    - by Mysticgeek
    Since there are three versions of Windows out in the field these days, chances are you need to share data between them. Today we show how to get each version to be share files and printers with one another. In a perfect world, getting your computers with different Microsoft operating systems to network would be as easy as clicking a button. With the Windows 7 Homegroup feature, it’s almost that easy. However, getting all three of them to communicate with each other can be a bit of a challenge. Today we’ve put together a guide that will help you share files and printers in whatever scenario of the three versions you might encounter on your home network. Sharing Between Windows 7 and XP The most common scenario you’re probably going to run into is sharing between Windows 7 and XP.  Essentially you’ll want to make sure both machines are part of the same workgroup, set up the correct sharing settings, and making sure network discovery is enabled on Windows 7. The biggest problem you may run into is finding the correct printer drivers for both versions of Windows. Share Files and Printers Between Windows 7 & XP  Map a Network Drive Another method of sharing data between XP and Windows 7 is mapping a network drive. If you don’t need to share a printer and only want to share a drive, then you can just map an XP drive to Windows 7. Although it might sound complicated, the process is not bad. The trickiest part is making sure you add the appropriate local user. This will allow you to share the contents of an XP drive to your Windows 7 computer. Map a Network Drive from XP to Windows 7 Sharing between Vista and Windows 7 Another scenario you might run into is having to share files and printers between a Vista and Windows 7 machine. The process is a bit easier than sharing between XP and Windows 7, but takes a bit of work. The Homegroup feature isn’t compatible with Vista, so we need to go through a few different steps. Depending on what your printer is, sharing it should be easier as Vista and Windows 7 do a much better job of automatically locating the drivers. How to Share Files and Printers Between Windows 7 and Vista Sharing between Vista and XP When Windows Vista came out, hardware requirements were intensive, drivers weren’t ready, and sharing between them was complicated due to the new Vista structure. The sharing process is pretty straight-forward if you’re not using password protection…as you just need to drop what you want to share into the Vista Public folder. On the other hand, sharing with password protection becomes a bit more difficult. Basically you need to add a user and set up sharing on the XP machine. But once again, we have a complete tutorial for that situation. Share Files and Folders Between Vista and XP Machines Sharing Between Windows 7 with Homegroup If you have one or more Windows 7 machine, sharing files and devices becomes extremely easy with the Homegroup feature. It’s as simple as creating a Homegroup on on machine then joining the other to it. It allows you to stream media, control what data is shared, and can also be password protected. If you don’t want to make your Windows 7 machines part of the same Homegroup, you can still share files through the Public Folder, and setup a printer to be shared as well.   Use the Homegroup Feature in Windows 7 to Share Printers and Files Create a Homegroup & Join a New Computer To It Change which Files are Shared in a Homegroup Windows Home Server If you want an ultimate setup that creates a centralized location to share files between all systems on your home network, regardless of the operating system, then set up a Windows Home Server. It allows you to centralize your important documents and digital media files on one box and provides easy access to data and the ability to stream media to other machines on your network. Not only that, but it provides easy backup of all your machines to the server, in case disaster strikes. How to Install and Setup Windows Home Server How to Manage Shared Folders on Windows Home Server Conclusion The biggest annoyance is dealing with printers that have a different set of drivers for each OS. There is no real easy way to solve this problem. Our best advice is to try to connect it to one machine, and if the drivers won’t work, hook it up to the other computer and see if that works. Each printer manufacturer is different, and Windows doesn’t always automatically install the correct drivers for the device. We hope this guide helps you share your data between whichever Microsoft OS scenario you might run into! Here are some other articles that will help you accomplish your home networking needs: Share a Printer on a Home Network from Vista or XP to Windows 7 How to Share a Folder the XP Way in Windows Vista Similar Articles Productive Geek Tips Delete Wrong AutoComplete Entries in Windows Vista MailSvchost Viewer Shows Exactly What Each svchost.exe Instance is DoingFixing "BOOTMGR is missing" Error While Trying to Boot Windows VistaShow Hidden Files and Folders in Windows 7 or VistaAdd Color Coding to Windows 7 Media Center Program Guide TouchFreeze Alternative in AutoHotkey The Icy Undertow Desktop Windows Home Server – Backup to LAN The Clear & Clean Desktop Use This Bookmarklet to Easily Get Albums Use AutoHotkey to Assign a Hotkey to a Specific Window Latest Software Reviews Tinyhacker Random Tips DVDFab 6 Revo Uninstaller Pro Registry Mechanic 9 for Windows PC Tools Internet Security Suite 2010 Icelandic Volcano Webcams Open Multiple Links At One Go NachoFoto Searches Images in Real-time Office 2010 Product Guides Google Maps Place marks – Pizza, Guns or Strip Clubs Monitor Applications With Kiwi

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  • Declarative Architectures in Infrastructure as a Service (IaaS)

    - by BuckWoody
    I deal with computing architectures by first laying out requirements, and then laying in any constraints for it's success. Only then do I bring in computing elements to apply to the system. As an example, a requirement might be "world-side availability" and a constraint might be "with less than 80ms response time and full HA" or something similar. Then I can choose from the best fit of technologies which range from full-up on-premises computing to IaaS, PaaS or SaaS. I also deal in abstraction layers - on-premises systems are fully under your control, in IaaS the hardware is abstracted (but not the OS, scale, runtimes and so on), in PaaS the hardware and the OS is abstracted and you focus on code and data only, and in SaaS everything is abstracted - you merely purchase the function you want (like an e-mail server or some such) and simply use it. When you think about solutions this way, the architecture moves to the primary factor in your decision. It's problem-first architecting, and then laying in whatever technology or vendor best fixes the problem. To that end, most architects design a solution using a graphical tool (I use Visio) and then creating documents that  let the rest of the team (and business) know what is required. It's the template, or recipe, for the solution. This is extremely easy to do for SaaS - you merely point out what the needs are, research the vendor and present the findings (and bill) to the business. IT might not even be involved there. In PaaS it's not much more complicated - you use the same Application Lifecycle Management and design tools you always have for code, such as Visual Studio or some other process and toolset, and you can "stamp out" the application in multiple locations, update it and so on. IaaS is another story. Here you have multiple machines, operating systems, patches, virus scanning, run-times, scale-patterns and tools and much more that you have to deal with, since essentially it's just an in-house system being hosted by someone else. You can certainly automate builds of servers - we do this as technical professionals every day. From Windows to Linux, it's simple enough to create a "build script" that makes a system just like the one we made yesterday. What is more problematic is being able to tie those systems together in a coherent way (as a solution) and then stamp that out repeatedly, especially when you might want to deploy that solution on-premises, or in one cloud vendor or another. Lately I've been working with a company called RightScale that does exactly this. I'll point you to their site for more info, but the general idea is that you document out your intent for a set of servers, and it will deploy them to on-premises clouds, Windows Azure, and other cloud providers all from the same script. In other words, it doesn't contain the images or anything like that - it contains the scripts to build them on-premises or on a cloud vendor like Microsoft. Using a tool like this, you combine the steps of designing a system (all the way down to passwords and accounts if you wish) and then the document drives the distribution and implementation of that intent. As time goes on and more and more companies implement solutions on various providers (perhaps for HA and DR) then this becomes a compelling investigation. The RightScale information is here, if you want to investigate it further. Yes, there are other methods I've found, but most are tied to a single kind of cloud, and I'm not into vendor lock-in. Poppa Bear Level - Hands-on EvaluateRightScale at no cost.  Just bring your Windows Azurecredentials and follow the these tutorials: Sign Up for Windows Azure Add     Windows Azure to a RightScale Account Windows Azure Virtual Machines     3-tier Deployment Momma Bear Level - Just the Right level... ;0)  WindowsAzure Evaluation Guide - if you are new toWindows Azure Virtual Machines and new to RightScale, we recommend that youread the entire evaluation guide to gain a more complete understanding of theWindows Azure + RightScale solution.    WindowsAzure Support Page @ support.rightscale.com - FAQ's, tutorials,etc. for  Windows Azure Virtual Machines (Work in Progress) Baby Bear Level - Marketing WindowsAzure Page @ www.rightscale.com - find overview informationincluding solution briefs and presentation & demonstration videos   Scale     and Automate Applications on Windows Azure  Solution Brief     - how RightScale makes Windows Azure Virtual Machine even better SQL     Server on Windows Azure  Solution Brief   -       Run Highly Available SQL Server on Windows Azure Virtual Machines

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  • Network throughput issue (ARP-related)

    - by Joel Coel
    The small college where I work is having some very strange network issues. I'm looking for any advice or ideas here. We were fine over the summer, but the trouble began few days after students returned to campus in force for the fall term. Symptoms The main symptom is that internet access will work, but it's very slow... often to the point of timeouts. As an example, a typical result from Speedtest.net will return .4Mbps download, but allow 3 to 8 Mbps upload speed. Lesser symptoms may include severely limited performance transferring data to and from our file server, or even in some cases the inability to log in to the computer (cannot reach the domain controller). The issue crosses multiple vlans, and has effected devices on nearly every vlan we operate. The issue does not impact all machines on the network. An unaffected machine will typically see at least 11Mbps download from speedtest.net, and perhaps much more depending on larger campus traffic patterns at the time. There is one variation on the larger issue. We have one vlan where users were unable to log into nearly all of the machines at all. IT staff would log in using a local administrator account (or in some cases cached credentials), and from there a release/renew or pinging the gateway would allow the machine to work... for a while. Complicating this issue is that this vlan covers our computer labs, which use software called Deep Freeze to completely reset the hard drives after a reboot. It could just the same issue manifesting differently because of stale data on machines that have not permanently altered low-level info for weeks. We were able to solve this, however, by creating a new vlan and moving the labs over to the new vlan wholesale. Instigations Eventually we noticed that the effected machines all had recent dhcp leases. We can predict when a machine will become "slow" by watching when a dhcp lease comes up for renewal. We played with setting the lease time very short for a test vlan, but all that did was remove our ability to predict when the machine would become slow. Machines with static IPs have pretty much always worked normally. Manually releasing/renewing an address will never cause a machine to become slow. In fact, in some cases this process has fixed a machine in that state. Most of the time, though, it doesn't help. We also noticed that mobile machines like laptops are likely to become slow when they cross to new vlans. Wireless on campus is divided up into "zones", where each zone maps to a small set of buildings. Moving to a new building can place you in a zone, thereby causing you to get a new address. A machine resuming from sleep mode is also very likely to be slow. Mitigations Sometimes, but not always, clearing the arp cache on an effected machine will allow it to work normally again. As already mentioned, releasing/renewing a local machine's IP address can fix that machine, but it's not guaranteed. Pinging the default gateway can also sometimes help with a slow machine. What seems to help most to mitigate the issue is clearing the arp cache on our core layer-3 switch. This switch is used for our dhcp system as the default gateway on all vlans, and it handles inter-vlan routing. The model is a 3Com 4900SX. To try to mitigate the issue, we have the cache timeout set on the switch all the way down to the lowest possible time, but it hasn't helped. I also put together a script that runs every few minutes to automatically connect to the switch and reset the cache. Unfortunately, this does not always work, and can even cause some machines to end up in the slow state for a short time (though these seem to correct themselves after a few minutes). We currently have a scheduled job that runs every 10 minutes to force the core switch to clear it's ARP cache, but this is far from perfect or desirable. Reproduction We now have a test machine that we can force into the slow state at will. It is connected to a switch with ports set up for each of our vlans. We make the machine slow by connecting to different vlans, and after a new connection or two it will be slow. It's also worth noting in this section that this has happened before at the start of prior terms, but in the past the problem has gone away on it's own after a few days. It solved itself before we had a chance to do much diagnostic work... hence why we've allowed it to drag so long into the term this time 'round; the expectation was this would be a short-lived situation. Other Factors It's worth mentioning that we have had about half a dozen switches just outright fail over the last year. These are mainly 2003/2004-era 3Coms (mostly 4200's) that were all put in at about the same time. They should still be covered under warranty, buy HP has made getting service somewhat difficult. Mostly in power supplies that have failed, but in a couple cases we have used a power supply from a switch with a failed mainboard to bring a switch with a failed power supply back to life. We do have UPS devices on all but three of four switches now, but that was not the case when I started two and a half years ago. Severe budget constraints (we were on the Dept. of Ed's financially challenged institutions list a couple years back) have forced me to look to the likes of Netgear and TrendNet for replacements, but so far these low-end models seem to be holding their own. It's also worth mentioning that the big change on our network this summer was migrating from a single cross-campus wireless SSID to the zoned approach mentioned earlier. I don't think this is the source of the issue, as like I've said: we've seen this before. However, it's possible this is exacerbating the issue, and may be much of the reason it's been so hard to isolate. Diagnosis At first it seemed clear to us, given the timing and persistent nature of the problem, that the source of the issue was an infected (or malicious) student machine doing ARP cache poisoning. However, repeated attempts to isolate the source have failed. Those attempts include numerous wireshark packet traces, and even taking entire buildings offline for brief periods. We have not been able even to find a smoking gun bad ARP entry. My current best guess is an overloaded or failing core switch, but I'm not sure on how to test for this, and the cost of replacing it blindly is steep. Again, any ideas appreciated.

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  • OpenVPN DNS: VPN DNS stomping local VPN

    - by Eddie Parker
    I've finally noodled with OpenVPN enough to get it working. Even better, I can mount samba drives, ping network machines through the TUN device, etc - it's all great. However, I'm noticing that if I have the directive: push "dhcp-option DNS 10.0.1.1" # Push our local DNS to clients Then some of the machines that are normally visible by the client, on the client's side (i.e., not through the VPN) get masked with some other server out on the Internet. Is there any way to avoid this, besides hacking the 'hosts' file on the client machine? Ideally I'd like to only use my VPN's DNS for machines within that domain.

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  • OpenVPN DNS: VPN DNS stomping local VPN

    - by Eddie Parker
    I've finally noodled with OpenVPN enough to get it working. Even better, I can mount samba drives, ping network machines through the TUN device, etc - it's all great. However, I'm noticing that if I use the following directive, then some of the machines that are normally visible by the client, on the client's side (i.e., not through the VPN) get masked with some other server out on the Internet. push "dhcp-option DNS 10.0.1.1" # Push our local DNS to clients Is there any way to avoid this, besides hacking the 'hosts' file on the client machine? Ideally I'd like to only use my VPN's DNS for machines within that domain.

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  • Host name resolution on a home network

    - by Kris
    Hi, I have several machines (both virtual and physical) in my internal network at home. Currently I have to connect via 1P addresses. The one main machine I connect with to all the other machines is running Windows Vista. Is there a way I can have some sort of DNS capability inside my network as well so I can refer to these machines with a name? I think this would be a common problem in most households (running a few computers) and I think there might be some simple solutions out there. This would be something most routers should support out of the box - but why don't they? Can anyone recommend some of these or an easy way to accomplish this?

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  • Host name resolution on a home network

    - by Kris
    Hi, I have several machines (both virtual and physical) in my internal network at home. Currently I have to connect via 1P addresses. The one main machine I connect with to all the other machines is running Windows Vista. Is there a way I can have some sort of DNS capability inside my network as well so I can refer to these machines with a name? I think this would be a common problem in most households (running a few computers) and I think there might be some simple solutions out there. This would be something most routers should support out of the box - but why don't they? Can anyone recommend some of these or an easy way to accomplish this?

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  • Connectivity good between VMs, but no connectivity between host and VM

    - by Greg Sansom
    I have a strange situation where connectivity (ie ping, access shared folders and services) is fine between virtual machines, but not between the host and the virtuals. I've been using Hyper-V almost every day for years and have never had a problem like this. Note the following: The host machine and all virtuals are running Windows Server 2008 r1. All machines can connect to the web, and the gateway router. Subnet mask and gateway reported in ipconfig are identical for all machines. I can access virtuals via the Hyper-V snap-in only. Doea anyone have suggestions about what might be wrong, or what diagnostic steps I can take?

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  • How to get diagnostic information on a failing Windows Server 2012 install

    - by Tobius Maximus
    I am trying to install a copy of Windows Server 2012 on two machines. Both machines go through the initial "Files loading" progress bar and get to the new Windows Server 2012 logo. However, the installation (on both machines) will immediately fail, and the machine will restart. I am trying to figure out if there's a way to display diagnostic information about the error before or after restarting, but Google is not helping me at all. Is there a key combination I can hit that will display an error log, perhaps?

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  • Connecting to Aerohive APs from Laptops running Win. 7 using authentication from a Windows 2008 domain server

    - by user264116
    I have deployed a wireless network using Aerohive access points. 2 of them are set up as radius servers. I want my users to be able to use the same user name and password they use when they log onto our domain. They are able to do this from android devices or computers running Windows 8. It will not work on Windows 7 machines. How do I remedy this situation, keeping in mind that the machines are personal machines not company owned and I will have no way to change their hardware or software.

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  • How to disable Tcp/Ip settings in windows 7 via GPO?

    - by Akash Kava
    I have enabled following policies, "Prohibit TCP/IP advanced connection" "Prohibit access to properties of components of a LAN connection" "Enable Windows 2000 Network Connections setings for Administrators" after doing all these, all machines running windows xp, 2000 and vista have network settings properties button disabled as expected. However all machines running windows 7 have no effect, I believe there are few more steps, all Windows 7 machines are on domain and we want to control this via Domain Controler's GPO. Please let me know, what I need to do to have Windows 7 disable the properties of network connection, I am not network expert, I read few articles about what new has been added in GPO of windows 7 but I am blank. Everything works fine on Windows XP, Vista, 2003 Server. Only Windows 7 is a problem.

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  • VmWare / Citrix Xen type environment vs Ubuntu Cloud / Amazon EC2 type environment.

    - by Nick Gorbikoff
    Hello. A bit of background. We run a small in house data center: about 20 virtualized servers (Debian Lenny, Windows 2003, Windows xp and Windows 7 machines), in a Citrix Xen pool running on 3 host servers and a SAN, plus a few standalone machines running legacy or specialized software that can't be vritualized. There is a big push everywhere now to move to cloud so we considering Ubuntu Cloud. I was wondering what are the pros / cons of running virtualized pool vs cloud to run all those machines? Thank you

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  • Server Core remote management from Windows 7 machine

    - by Robert Koritnik
    I've installed Remote Server Administration Tools for Windows 7 because I would like to administer my Windows Server 2008 R2 Server Core machine. The problem that I'm getting when I try to run Server Manager is: Connecting to remote server failed with the following error message: Access is denied. For more information, see the about_Remote_Troubleshooting Help topic. This is what I've done so far: I'm running WinRM service on both machines (Server and Window 7) I've added my server to trusted hosts on my Windows 7 machine: winrm set winrm/config/client @{TrustedHosts="WINSRV2"} I've added registry entry on Windows 7 machine: reg add HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System /v LocalAccountTokenFilterPolicy /t REG_DWORD /d 1 /f I've enabled Remote Management inbound rule on server firewall using CoreConfigurator 2.0 both machines are in the same subnet and when I search for network machines on Windows 7 I see my server. Question What else should I do to make it work? I would like to run several different remote management tools against my server machine.

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  • Is the field BusID necessary in XF86Config?

    - by Greg
    Hello, I am using a cluster of machines running on Ubuntu 10.04 LTS which are supposed to be homogeneous, but apparently they are not. In particular, I am configuring the X server on these machines, and I pushed a /etc/X11/XF86Config that includes the following section: Section "Device" Identifier "Device0" Driver "nvidia" VendorName "NVIDIA Corporation" BusID "PCI:5:0:0" EndSection The problem is that the BusID of the graphic card is PCI:5:0:0 for some machines, and PCI:3:0:0 for others. Is there a way that the X server automatically detects the appropriate Device (based on the name for instance)? Thanks,

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  • Can you help me think of problems for my programming language?

    - by I can't tell you my name.
    I've created an experimental toy programming language with a (now) working interpreter. It is turing-complete and has a pretty low-level instruction set. Even if everything takes four to six times more code and time than in PHP, Python or Ruby I still love programming all kinds of things in it. So I got the "basic" things that are written in many languages working: Hello World Input - Output Countdowns (not as easy as you think as there are no loops) Factorials Array emulation 99 Bottles of Beer (simple, wrong inflection) 99 Bottles of Beer (canonical) Conjatz conjecture Quine (that was a fun one!) Brainf*ck interpreter (To proof turing-completeness, made me happy) So I implemented all of the above examples because: They all used many different aspects of the language They are pretty interesting They don't take hours to write Now my problem is: I've run out of ideas! I don't find any more examples of what problems I could solve using my language. Do you have any programming problems which fit into some of the criteria above for me to work out?

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  • What should be taken into consideration when deploying Windows 8 in a domain environment?

    - by GaTechThomas
    Edit: Reformulating the question: We have ordered new laptops but before they arrive, our development team is trying to decide whether to install Windows 8 or stick with Windows 7. We have already tested on isolated machines, but we have not yet been allowed to add the machines to the domain. Before we approach the networking group to discuss adding Windows 8 machines to the domain, we need more information on what changes / issues to expect in moving from Windows 7. Are there any aspects we should consider that are specific to Windows 8 clients? Thus far, I've gotten the following feedback: Windows Administrative Shares are disabled New set of Group Policy templates Changes to proxy server settings Additional items along these lines would be helpful. We're not looking for items related to Windows GUI changes, but instead primarily items related to having the machine live and be used on the domain.

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  • Running 'sudo' over SSH

    - by Wesho
    I'm writing a script which is to log onto a bunch of remote machines and run a command on them. I've set up keys so the user running the script does not have to type the password of each machine, but only type in the passphrase in the beginning of the script. The problem is that the command on the remote machines requires sudo to run. And at the same time the whole point of the script is to rid the user of having to type in passwords multiple times. Is there way to avoid typing in the password for sudo? Changing permissions of the command on the remote machines is not an option.

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  • Track IP Messenger's chatting by wireshark

    - by Kumar P
    We have Linux server ( RHEL 5 ), and some client machines ( Windows XP ) in local area network. We using server as proxy server. I am using squid proxy. My windows machines using internet by proxy. Now my client machines using IP messenger for chatting and sharing files with in local network. How can i trace what they are doing or chatting by ip messenger, from my server by wireshark packet sniffer ? If i can't do it by wireshark , What will you give idea about it...

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  • secure synchronization of large amount of data

    - by goncalopp
    I need to automatically mirror a large amount (terabytes) of files in two unix machines over a slow link (1 Mbps). This needs to be done frequently, but the data doesn't change too much (delta transmission doesn't saturate the link). The usual solution would be rsync, but there's an additional requirement: it's undesirable, from a security standpoint, that either the source or destination machines have (keyless) ssh keys to each other, or any kind of filesystem access. All communication between the two machines should thus be initialized (and mediated) through a third machine. I've asked a separate question about rsync in particular here. Are there other obvious solutions I'm missing?

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