A close friend of mine works as the IT manager for a construction company. He mentioned an interesting incident that happened at his office. He was facing problems with a few systems at his office. When users try to send emails, most of the time the mail would get stuck in outbox and not finish sending. It will finish only after he re-opened and sent it again or if he restarted outlook. He tried a lot of things to get it fixed like re-installing and even changing his internet router! Changing the router solved a lot of other problems but not this one! he did notice something odd. While trying to send , outlook would show Sending 1/800 or some huge number, but the number of items in Outbox was not more than 10. After a little bit of googling, he found a article which talked abt read receipts. it also talked abt a tool to check the number of pending read receipts, and cancel them manually. When he ran the tool on one system he found 600+ read receipts pending. After a boring few hours of manually clearing all the read receipts, outlook started working without any hassles.
Friday, November 12, 2010
Cisco switches and virtual machines
A very interesting thing happened recently. A server running on centos , was setup as a base OS for 3 windows virtual machines - a domain controller, a database server, and an antivirus server. Last week the database server stopped responding. A restart didn't solve the problem. Even pinging didn't work. So the admin decided to restart the physical server itself. After the restart all the virtual machines stopped responding! A few more restarts , and checks on the network settings of the physical server, vm and there was no change. The admin disabled the physical network card and restarted the vms and servers. After re enabling the card suddenly the dc started responding and the physical server stopped responding! That's when the admin decided to take a break and re-assess the situation.
He had one physical server, and 3 vms. One of the vms was responding on the LAN. The physical server and the other two vms were not responding to any requests. But he had done restarts before and this was a new thing. The only change he could point out was that he had replaced one of the 3com switches with a cisco 2900 managed switch. This was to setup a gigabit uplink. It was a shot in the dark but we removed the server network cable from the cisco switch and plugged it into another 3com switch in the rack, and presto , all the servers and vms started responding. :) after doing a bit of reading, a particular setting on the cisco sets it to accept traffic only from one IP per port. that's why even though the dc was responding, the physical server was not allowed to respond.
Now that's what I call security. Good stuff, cisco!
Sent from my BlackBerry® smartphone from VIVA
He had one physical server, and 3 vms. One of the vms was responding on the LAN. The physical server and the other two vms were not responding to any requests. But he had done restarts before and this was a new thing. The only change he could point out was that he had replaced one of the 3com switches with a cisco 2900 managed switch. This was to setup a gigabit uplink. It was a shot in the dark but we removed the server network cable from the cisco switch and plugged it into another 3com switch in the rack, and presto , all the servers and vms started responding. :) after doing a bit of reading, a particular setting on the cisco sets it to accept traffic only from one IP per port. that's why even though the dc was responding, the physical server was not allowed to respond.
Now that's what I call security. Good stuff, cisco!
Sent from my BlackBerry® smartphone from VIVA
Wednesday, October 20, 2010
Untangle
A good friend of mine, Hussain, brought up an issue at one of his sites. The users were using up all the bandwidth, and he wanted an option where could control bandwidth and traffic. He basically listed a few requirements :
1. Bandwidth control
2. Content Filtering
3. Central user control
Having worked with Microsoft technologies for sometime, I was tempted to suggest Forefront 2010. But he had mentioned that this was just an internet-sharing, non-domain enviroment. So I started looking elsewhere,and after a bit of googling, I came across Untangle (www.untangle.com). It's an open-source firewall/router with a few nice plugins that come for free, and some awesome plugins that you have to pay for.
I downloaded the ISO (450Megs for the 32-bit version) , and burnt a CD. Once we setup a PC for use, I popped in the CD and started the install. Untangle comes in a few versions ,(1.Standalone OS - based on Debian, 2. Windows based.,etc). Since this PC was not going to be used for anything else, I started the Standalone OS install. The installation was pretty simple with a few prompts for hard disk partitioning and some features. After I rebooted into the OS, then the setup wizard started, asking about network settings.
I entered the required settings, then the base OS came into view. The base OS is nicely designed with a dock at the bottom,showing the client icon and icons for terminal, reboot and shutdown.
You will be using the client mainly, which is a web-based client that opens up in Iceweasel.
After the first login, you will be asked to select the app packages that you want to install. They have a few questions as to what your installation will be used for, and then selects that packages based on your answers. You can customize the final selection , and start the download. There are a few big plugins, so be prepared to wait for the download to complete. I discovered this the hard way. While downloading the packages, I started playing the ADSL router settings, and in between I had to reset the router. I expected the download to resume on it's own. But it didn't :). So the package installation came up with an error message stating that apt-get exited with a code of 1! I tried restarting the package installation, but the error message came up again. So I was back on google, trying to find a solution. The untangle forums were very helpful, and the package installation procedure is properly logged in the log directory. I opened terminal and ran a command mentioned in the forums tail -n 100 -f /var/log/uvm/apt.log. This showed that one of the packages was not finishing it's installation. So I deleted the package, and restarted the download manually, using the apt-get command.Once the download completed properly, I could download apps using the GUI.
The interface is well designed and easy to navigate.
We've put up the rules,and the firewall was responding properly. The installation is still under testing, let's see how the response is.
1. Bandwidth control
2. Content Filtering
3. Central user control
Having worked with Microsoft technologies for sometime, I was tempted to suggest Forefront 2010. But he had mentioned that this was just an internet-sharing, non-domain enviroment. So I started looking elsewhere,and after a bit of googling, I came across Untangle (www.untangle.com). It's an open-source firewall/router with a few nice plugins that come for free, and some awesome plugins that you have to pay for.
I downloaded the ISO (450Megs for the 32-bit version) , and burnt a CD. Once we setup a PC for use, I popped in the CD and started the install. Untangle comes in a few versions ,(1.Standalone OS - based on Debian, 2. Windows based.,etc). Since this PC was not going to be used for anything else, I started the Standalone OS install. The installation was pretty simple with a few prompts for hard disk partitioning and some features. After I rebooted into the OS, then the setup wizard started, asking about network settings.
I entered the required settings, then the base OS came into view. The base OS is nicely designed with a dock at the bottom,showing the client icon and icons for terminal, reboot and shutdown.
You will be using the client mainly, which is a web-based client that opens up in Iceweasel.
After the first login, you will be asked to select the app packages that you want to install. They have a few questions as to what your installation will be used for, and then selects that packages based on your answers. You can customize the final selection , and start the download. There are a few big plugins, so be prepared to wait for the download to complete. I discovered this the hard way. While downloading the packages, I started playing the ADSL router settings, and in between I had to reset the router. I expected the download to resume on it's own. But it didn't :). So the package installation came up with an error message stating that apt-get exited with a code of 1! I tried restarting the package installation, but the error message came up again. So I was back on google, trying to find a solution. The untangle forums were very helpful, and the package installation procedure is properly logged in the log directory. I opened terminal and ran a command mentioned in the forums tail -n 100 -f /var/log/uvm/apt.log. This showed that one of the packages was not finishing it's installation. So I deleted the package, and restarted the download manually, using the apt-get command.Once the download completed properly, I could download apps using the GUI.
The interface is well designed and easy to navigate.
We've put up the rules,and the firewall was responding properly. The installation is still under testing, let's see how the response is.
In the beginning, there was a blog!
4+ years of being a system admin takes its toll on the mind. It's always been in the back of my mind to put down atleast some of the experiences I've had, with regards to IT that is. Bahrain, being a small island in the Arabian Gulf, and my home for the most of my life, doesn't really provide a HUGE amount of opportunities to experience IT in it's entirety. You could pin it on the laid-back attitude of people in embracing new forms of technology, or just the lack of resources for support and encouragement. This is just my opinion btw. I'm definitely interested in hearing an argument on this subject.
So as of now, I'm going to start penning down my IT experiences , and maybe I'll look back at it after a few years and smile!
To infinity and beyond!!!....
So as of now, I'm going to start penning down my IT experiences , and maybe I'll look back at it after a few years and smile!
To infinity and beyond!!!....
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