I ran across this link http://www.mtit.com/resources/teamblogs.htm wihle browsing the web. It has a list of Microsoft Team blogs, where teams from certain business areas in Microsoft write on certain applications or areas. One that I visit on a regular basis is the Exchange Team Blog at http://blogs.technet.com/exchange/. Lots of good material there..
Technology
IP Address confusion and DHCP
Ran into a good case of Network troubleshooting today. We use the private 192.168.0.0/16 address range at work. All of a sudden, we had users calling us from a particular floor stating that they cannot access network resources. Here’s how the team solved the issue
1) Physical connectivity – Is the cable plugged into the workstation? Is there a green light on the NIC?
2) DNS Lookup – Open a command prompt and do a look up on a server in the network. In this case, one of our file servers. Users say that they are getting a “server inaccessible” error. Hmm.. Alright, so we have physical connectivity, but don’t have DNS resolution. Since the rest of the user population didn’t have any DNS resolution issues, the team dug deeper
3) IP Address Details – Open a command prompt and type in “ipconfig”. This showed that the affected users were getting a “172.16.0.x” address. This range does not exist in our user network segment. So looks like we have users getting an unqualified network. Since all users are configured to get their IP addresses through DHCP, the culprit might be DHCP.
4) DHCP Server : The Issue – Open a command prompt and type in “ipconfig /all”. This showed the following
Aha.. looks like there is a rouge DHCP server in our network. The team checked the LAN room on the floor and found the culprit server. Looks like the server was installed in it’s default state where it acted as a DHCP server.
Lesson learnt : DHCP broadcasts sent by the client are addressed by servers in the same broadcast (Layer 2) domain before being routed to other DHCP servers (IP Helper Addresses).
Windows : Explore running processes
One of the Windows server at work started running high on CPU for the last few days.. On checking the task manager, I could only see that “services.exe” was using ~30% of CPU. services.exe is part of the core Windows operating system and manages the starting and stopping of the services. To further investigate, what process was using the CPU, I lauched Sysinternals Process Explorer and voila!!, here’s what I see
Looks like the CPU utilization of the services that the services.exe starts show up under it. There are a bunch of other cool utilities at SysInternals that any Windows admin would find useful.
Party time..
I think it is high time I started using Flickr to post my pictures. I take a ton of pictures (yes, I am one of those crazy guys, that carry a camera on them ALL the time) and haven’t found a way to share them with friends and family without maxing out the traffic on my hosted site. I have been looking at all the photo sharing, social tagging sites such as flickr, fotki, hello for quite some time, but never got around to creating an account and using them. I don’t like sites that require you to register just to look at pictures (kodak!!). We have too many accounts as it is, without having to register on a site just to look at some photos.
Long post short :).. Here is the first attempt to start logging my pictures online. The link to my pictures on flickr is
http://www.flickr.com/photos/kudithipudi/sets/72057594092170857/
P.S: If anyone wants me to delete their photos, pls shoot me an E-mail at vinay at kudithipudi dot org. Thx.
Updating NFS Share permissions..
Wanted to add this for my future reference. To update the permissions on a NFS (Network File System) share, you need to edit the “/etc/exports” file and then run “/usr/sbin/exportfs -a” to update the share permissions.
Syntax of /etc/exports looks like
/dir/to/export host1.mydomain.com(ro,root_squash)
UPDATE : Looks like the NFS daemon caches DNS lookups when authenticating a client. Am not sure if this is only in older versions. After we updated the exports file, the server still kep erroring out with a “unresolvable reverse lookup” error. I finally had to restart the daemon to make it check on the DNS records for the accessing client.
What is NPA NXX ?
I am in the middle of ordering some data circuits for our new office and the vendor asks me for the address of the building where the circuits are going to be terminated. I give it to them and they come back with “what is the NPA NXX??” of the location. Now, I should admit that I haven’t been provisioning hardcode data circuits, but have ordered a bunch of T1s and DS3s during my career. I thought this was come kind of technical spec and swallowing my pride, asked the vendor what NPA NXX means.. and the answer..
“there are no dumb questions 🙂
the first six digits of a phone number“
the first six digits of a phone number“
Looking up on the web, gave me this information
NPA = (Numbering Plan Area code) The area code of a telephone number in the NPA system. The first NPA codes used 0 or 1 as the center digit, such as 201, 212, 301, 312, etc., designated as “N0/1X.” After July 1, 1995, all digits 0 through 9 are valid as the center digit, designated as “NXX.”
All I can say is “live and learn” :).
UBUNTU : Quick tips
I have heard a lot about the new Linux distro Ubuntu and wanted to try it out on my test machine at home. I chose the “base” install, which apparently just installs the base packages to operate the machine as a server. Couple of things I had to do to get the system up and running
1) The root account in Ubuntu doesn’t have a password by default. This means that you cannot log in or “su” to root. This can be fixed by issuing the following command
“sudo passwd root”
while logged in as the user you create while installing Ubuntu
2) Configure the network interface (eth0, if you only have one) with a static IP address. This can be done by editing the “interfaces” file in “/etc/network“. My file looks as below after the edit
| # This file describes the network interfaces available on your system # and how to activate them. For more information, see interfaces(5).# The loopback network interface auto lo iface lo inet loopback# This is a list of hotpluggable network interfaces. # They will be activated automatically by the hotplug subsystem. mapping hotplug script grep map eth0 # The primary network interface |
The text in bold is what I edited
3) Configure apt-get (package installer) to use the Internet archives as the source. This is esp. useful if you don’t have the install CD anymore. This can be done by editing the “sources.list” file located in “/etc/apt/” and commenting out the line with cdrom as the source. In my case it looks like this
“# deb cdrom:[Ubuntu 5.04 _Hoary Hedgehog_ – Release i386 (20050407)]/ hoary main restricted“. If you have a different version of Ubuntu, the description might be different, but the source should still say deb cdrom.
Blogging from a browser
One of the challenges I have in writing blogs is choosing the right editor. I have been using w.Blogger to far and have been very satisfied with it. But it is an additional program that I have to install and launch. With the powerful flexibility that Firefox provides, I have been trying moving all my “functions” to it. I use the multiple search engine functionality built into it. I just discovered “performancing.com” today. It is a firefox addon to publish blogs.. Hooho.. Open source rules.