Samba is an opensource suite that provided file and printer services in a  heterogeneous environment ( with  Windows , Unix and Linux). The key advantage of samba service is, it’s ability to provide file and print shares for both Windows and Unix clients equally. My main focus of this post is how to configure samba services integrated with Windows active directory services, so that samba user authentication will be performed by Windows Active Directory Services.

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Virtual LANs or VLANs are virtual separations within a switch that provide distinct logical LANs that each behave if there were configured on a separate physical switch. Some Important points about VLANS.

•  All the servers connected with in a VLAN will have same broadcasting domain, and can connect to each other directly
•  Servers belongs to different VLANs has to communicate with each other using external Routing device.  
•  To Expand the VLAN across multiple physical switches, physical switches needs to be interconnected using links called Trunks

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Network connection problems include slow connections, as well as complete loss of connectivity. Factors that may cause slow connectivity include incorrectly configured domain name system (DNS) settings, inefficiently configured routing tables, inferior cabling, overloaded servers, and network congestion. The same set of factors, as well as power or server failures, may result in complete loss of connectivity.

To troubleshoot a network connectivity problem, you should first check for the presence of a physical connection. If the network interface card (NIC) link light on a system is off, it indicates that no physical connection exists. This may result from

the use of incompatible or damaged cables
loose or unplugged cables
loss of power to a network switch or router
Troubleshooting interface problems

Linux tools you can use to troubleshoot network interface problems include

• ifconfig -  Used to determine the status of NICs.Without arguments, this command returns the status of all active interfaces. If you specify the name of an interface, it returns the status only of that interface. With the -a argument, the command displays the status of all interfaces on a computer, including any that may be inactive. This is the basic syntax for using the ifconfig command: ifconfig [interface] [options]
• mii-tool – The mii-tool utility enables you to display and manipulate the media-independent interface status. In its simplest form, you can use it to display the status of the interface’s link. This is the basic syntax for using the mii-tool command: mii-tool [options] [interface]
• ethtool – The ethtool utility is a diagnostic tool that enables you to configure and diagnose problems with NICs. However, not all NICs support its use. This is the basic syntax for using the ethtool command: ethtool [options] interface Full Story

Network connectivity checks For the server without OS  ( just Racked hardware and powered up)

For X86 Hardware

We have to make LED checks – like when we disconnect the cable at the server side / switch side the Link / Act LEDs should lit up on powered on machines.

For Sparc based Servers:

We can watch individual interfaces to see if they have a connection and can ‘see’ the network. At the OBP prompt on the client, use the “watch-net-all” command to test and see the network devices.

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In this post I am just talking about top 10 networking services that are commonly used in enterprise linux networks. Below are the top 10 Services, and it is worthwhile to know for the beginners to understand the purpose of each service, procedure to manage this service and the corresponding configuration files for each service.

•  ntpd – Network Time Protocol Daemon
• httpd – Hyper Text Transfer Protocol Daemon
• sshd – Secure SHell Daemon
• sendmail – Mail Server Daemon
• snmpd – Simple Network Management Protocol Daemon
• iptables – Network Filtering Protocol Service
• nfsd – Network File System Server Daemon
• nscd – Name Service Cache Daemon
• named – Dynamic Naming Service Server Daemon
• smbd -  Simple Message Block Server Daemon

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This is post is to explain the  configuration of  a linux VM with a secondary NIC  without reboot or restart network services. This is fairly simple and straight forward task, but I am just posting it for the folks who are new for the Linux VM on Vmware.

Unlike physical systems you don’t need to shutdown the box to add new physical NIC card ( just in case if you don’t have enough on board interface) . Once the VMWARE engineer creates a Virtual NIC on Hypervisor and attach it to our system, linux will automatically recognize the new device and will show you in the ifconfig output.

In the blow example, the scenario is we are actually configuring a secondary interface and attaching a network IP to it, and then we are adding additional static routes for the secondary IP.
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