Bonding is a feature that can be enabled bu the Linux kernel, to allow system administrators to combine two or more network interface to form a single, logical “bonded” interface, for redundancy or increased throughput purpose.

We can configure Linux bonding in 7 different modes. The behavior of the bonded interfaces depends upon the mode.

Below are the available bonding modes

• Balance-rr (mode 0)
• Active-backup (mode 1)
• Balance-xor (mode 2)
• Broadcast (mode 3)
• 802.3ad (mode 4)
• Balance-tlb (mode 5)
• Balance-alb (mode 6) Full Story

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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Red Hat Enterprise Linux 4.5 and previous

On a default installation the package Sysreport should be already installed. If not you need to install the package “sysreport-.rpm” with the following command

# rpm -ivh sysreport-.rpm

or, if your system is registered at the Red Hat Network “RHN”, simply running

# up2date -i sysreport

This will install the latest version of Sysreport on your system.

To collect the information you need to start troubleshooting just enter the command

# sysreport

and follow the instructions on screen. At the end you get a filename and the location where to find the compressed information collected by this script. Please keep this data for further support.

Please note that Sysreport will need some time to collect all the data, depending on the speed of the system and how many packages are installed.

In cases you experience that Sysreport seems to hang and will not return after a while, you may pass the parameter “-norpm” to the command. This will skip the checking of the RPM database which may be broken. Full Story

The General problem that we see in an enterprise environment, where there is no centralized automated password management tool is  …. missing root passwords for the servers.

Missing root passwords are also common when the servers initially managed by one team and later handed over to other team, but not all the changes to root passwords are not handed over to new teams. Full Story

Installing required packages

RHEL 5 has the Kdump packages installed by default. If for any reason they are not installed, you need to install the packages “kexec-tools-.rpm” and “system-config-kdump-.rpm” with the following commands:

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