Networking

Configuring VLANs in Linux

Turn off the Network Manager

#chkconfig NetworkManager off

goto directory “/etc/sysconfig/network-scripts/” and edit ifcfg-eth0 or ifcfg-eth1.

#cd /etc/sysconfig/network-scripts/
#vi ifcfg-eth0
DEVICE=eth0
TYPE=Ethernet
ONBOOT=yes
NM_CONTROLLED=no
BOOTPROTO=none
HWADDR=00:0C:29:CA:19:29
HOTPLUG=no
IPADDR=10.10.1.230
PREFIX=24
IPV4_FAILURE_FATAL=yes
IPV6INIT=no
IPV6_AUTOCONF=no
NAME="Ethernet1"
VLAN=yes

For creating VLAN with ID=300

#cp ifcfg-eth0 ifcfg-eth.300          //copy file and rename it to eth.vlanid
#vi ifcfg-eth.300
DEVICE=eth0.300
TYPE=Ethernet
ONBOOT=yes
NM_CONTROLLED=no
BOOTPROTO=none
HWADDR=00:0C:29:CA:19:29
HOTPLUG=no
IPADDR=10.10.2.230
PREFIX=24
IPV4_FAILURE_FATAL=yes
IPV6INIT=no
IPV6_AUTOCONF=no
NAME="VLAN300"
VLAN=yes

Then

#service network restart

You can create more VLANs by creating more files ifcfg-eth0.VLANID and replacing it with VLAN ID.

Detect Packet Errors In LAN Connection Status

Many of us are already using fast broadband connections these days and it’s important to know whether the information you are sending or receiving is correct and error free. When there is an error in sending or receiving data you might have problems downloading or uploading files and they could fail MD5 checksums or appear corrupt and the downloaded Zip or Rar archive won’t open etc. For example, if you keep getting errors sending packets but not receiving, then that could actually point to a faulty network adapter.

 

Error information can be an important first step in troubleshooting a connection. It’s very easy to view the basic network connection information, and you can see a network connection’s current status, connection duration, speed and packets or bytes sent and received for the connection. This is usually found by double-clicking the status icon in the system tray or going through Network and Sharing Center > Change adapter settings in Vista and above. The Status dialog box by default shows nearly everything but weirdly chooses not to display errors for the connection.

local area connection status

Before using sophisticated or tough to use packet sniffing software to detect packet loss and errors, you can just enable a hidden setting in Windows to show you any possible errors with your connection. Here’s how to do it with a quick registry change and the information will be added to the status dialog window.

[Read More: Full article by Raymond.cc]

TamoSoft Throughput Test

TamoSoft Throughput Test is a utility for testing the performance of a wireless or wired network. This utility continuously sends TCP and UDP data streams….

Click for more screen shots

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TCP Packet Replay & Editor

Tcpreplay is a suite of BSD GPLv3 licensed tools written by Aaron Turner for UNIX (and Win32 under Cygwin) operating systems which gives you the ability to use previously captured traffic in libpcap format to test a variety of network devices. It allows you to classify traffic as client or server, rewrite Layer 2, 3 and 4 headers and finally replay the traffic back onto the network and through other devices such as switches, routers, firewalls, NIDS and IPS’s. Tcpreplay supports both single and dual NIC modes for testing both sniffing and inline devices.

 

Tcpreplay is used by numerous firewall, IDS, IPS and other networking vendors, enterprises, universities, labs and open source projects. If your organization uses Tcpreplay, please let me know who you are and what you use it for so that I can continue to add features which are useful.

 

The Tcpreplay suite includes the following tools:

  • tcpprep – multi-pass pcap file pre-processor which determines packets as client or server and creates cache files used by tcpreplay and tcprewrite
  • tcprewrite – pcap file editor which rewrites TCP/IP and Layer 2 packet headers
  • tcpreplay – replays pcap files at arbitrary speeds onto the network
  • tcpliveplay – Replays network traffic stored in a pcap file on live networks using new TCP connections
  • tcpreplay-edit – replays & edits pcap files at arbitrary speeds onto the network
  • tcpbridge – bridge two network segments with the power of tcprewrite
  • tcpcapinfo – raw pcap file decoder and debugger

[Read More]