Tag Archive for Networking

OpenBSD: Reload / Restart / Stop dhcpd Server Command

I manage MS-Windows server and recently started to play with OpenBSD server. How do I reload or restart the dhcpd server on OpenBSD using shell command line option?

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CentOS / RHEL: Install iftop To Display Bandwidth Usage Per interface By Host

I am running Red Hat Enterprise Linux on IBM based system. How do I display bandwidth usage on an interface by host in real time using command line option? How do I monitor bandwidth usage in a real time on RHEL or CentOS Linux based server? How can I install iftop utility on CentOS or RHEL server using the yum command?

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Bringing up interface eth0: Device eth0 does not seem to be preset, delaying initialization – centos 6

ethernet_cable

This normally happens when you clone the machine and boot from another hardware

Bringing up interface eth0: Device eth0 does not seem to be preset, delaying initialization.      [FAILED]

To fix this, we need to update udev’s mapping rules to point the eth0 definition to the device with the correct MAC address. Open the file /etc/udev/rules.d/70-persistent-net.rules. You should see something similar to what is below:

view source
print?
01 # This file was automatically generated by the /lib/udev/write_net_rules
02 # program, run by the persistent-net-generator.rules rules file.
03 #
04 # You can modify it, as long as you keep each rule on a single
05 # line, and change only the value of the NAME= key.
06
07 # PCI device 0×8086:0x100f (e1000) (custom name provided by external tool)
08 SUBSYSTEM==”net”, ACTION==”add”, DRIVERS==”?*”, ATTR{address}==”00:50:56:9c:00:16″, ATTR{type}==”1″, KERNEL==”eth*”, NAME=”eth0″
09
10 # PCI device 0×8086:0x100f (e1000) (custom name provided by external tool)
11 SUBSYSTEM==”net”, ACTION==”add”, DRIVERS==”?*”, ATTR{address}==”00:50:56:9c:00:18″, ATTR{type}==”1″, KERNEL==”eth*”, NAME=”eth1″

As you can see there are two PCI ethernet adapters present.

 

1 # This file was automatically generated by the /lib/udev/write_net_rules
2 # program, run by the persistent-net-generator.rules rules file.
3 #
4 # You can modify it, as long as you keep each rule on a single
5 # line, and change only the value of the NAME= key.
6
7 # PCI device 0×8086:0x100f (e1000) (custom name provided by external tool)
8 SUBSYSTEM==”net”, ACTION==”add”, DRIVERS==”?*”, ATTR{address}==”00:50:56:9c:00:18″, ATTR{type}==”1″, KERNEL==”eth*”, NAME=”eth0″

You’ll also want to update the /etc/sysconfig/network-scripts/ifcfg-eth0 file to reflect the correct MAC address. Then, after a quick system restart your eth0 adapter will be back up.

 

Solaris / Linux: nicstat Command Show Network Interface Card Statistics

nicstat-welcomeThe nicstat command is top like utility for network interface card (NIC). It displays information and statistics about all your network card such as packets, kilobytes per second, average packet sizes and more. It works under Solaris and Linux operating systems.

In this post, I will explain how to install and use the nicstat command to find out stats about your NICs under Debian / Ubuntu / RHEL / CentOS Linux operating systems.

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