Change MAC Address on Linux (Ubuntu / Debian)

Temporary MAC Address Change

When you change the MAC address for an interface, you need to have the network interface disabled (down) and than to set the new MAC.

You can do both this things with the command:

$ sudo ifconfig eth0 down hw ether AA:BB:CC:DD:EE:FF && ifconfig eth0 up

This sets down the eth0 interface, changes the mac to AA:BB:CC:DD:EE:FF and turns the interface back down.

Or, do it in the old fashioned way:

$ sudo ifconfig eth0 down
$ sudo ifconfig eth0 hw ether AA:BB:CC:DD:EE:FF
$ sudo ifconfig eth0 up

Read more about the ifconfig command here.

 

Permanent MAC Address Change

To set the hardware address (MAC), open the /etc/network/interface file in your favourite text editor:

$ sudo vim /etc/network/interfaces

After the network interface configuration, paste this line: hwaddress ether AA:BB:CC:11:22:33.
Note: AA:BB:CC:11:22:33 is just a sample, replace it with the MAC address you want to set for your interface.

Example, with dhcp enabled network interface:

auto eth0
iface eth0 inet dhcp
hwaddress ether AA:BB:CC:11:22:33

Example, with a network interface having a static ip:

auto eth0
iface eth0 inet static
address 192.168.0.100
netmask 255.255.255.0
network 192.168.0.0
broadcast 192.168.0.255
gateway 192.168.0.1
hwaddress ether AA:BB:CC:11:22:33

To apply the MAC change, restart the network interface:

$ sudo /etc/init.d/networking restart

Based On:

• http://linuxg.net/set-the-mac-address-in-ubuntu-and-debian/
• http://linuxg.net/3-ways-to-temporary-change-the-mac-address-in-linux-and-unix/

Linux Switch (aka Bridge)

In this post Im going to show you how to configure a bridge (switch) in Linux. Here I will present several variations tha I have tested. The base cenário is the following:

# Set the eth1 IP address on the Rigth Laptop

ifconfig eth1 10.0.0.1 netmask 255.0.0.0

# Set the eth1 IP address on the Left Laptop

ifconfig eth1 10.0.0.2 netmask 255.0.0.0

Cenário 1 – No IPs on the Server NICs and Bridge

Server Configuration

# Load the bridge kernel module
modprobe bridge

# Activate eth1 and eth2 interface
ifconfig eth1 up

ifconfig eth2 up

# Create the bridge (virtual interface)
brctl addbr br0

# Add members to the bridge

brctl addif br0 eth1
brctl addif br0 eth2

Cenário 2 – No IPs on the Server NICs

Server Configuration

# Load the bridge kernel module
modprobe bridge

# Activate eth1 and eth2 interface
ifconfig eth1 up

ifconfig eth2 up

# Create the bridge (virtual interface)
brctl addbr br0

# Add members to the bridge
brctl addif br0 eth1
brctl addif br0 eth2

# Set the bridge IP address:
ifconfig br0 10.0.0.3 netmask 255.0.0.0

Now both computers are on the same LAN and can ping each other and the bridge interface, but can’t ping with the server NICs. This is like a switch with management ip.

Cenário 3 – IPs on the Server NICs and Bridge

Server Configuration

# Load the bridge kernel module
modprobe bridge

# Activate eth1 and eth2 interface
ifconfig eth1 up

ifconfig eth2 up

# Create the bridge (virtual interface)
brctl addbr br0

# Add members to the bridge
brctl addif br0 eth1
brctl addif br0 eth2

# Set the bridge IP address:
ifconfig br0 10.0.0.3 netmask 255.0.0.0

# Set the bridge IP address:
ifconfig br0 10.0.0.3 netmask 255.0.0.0

# Set the eth1 and eth2 IP address:
ifconfig eth1 10.0.0.4 netmask 255.0.0.0

ifconfig eth2 10.0.0.5 netmask 255.0.0.0

Now both computers are on the same LAN and can ping each other, the bridge interface, and also ping with the server NICs. It's like no switch I have ever seen.

Based On: http://openmaniak.com/openvpn_bridging.php

NIC Auto-Negotiation and Duplex Settings - NIC satus

FAQ: How to change Duplex and/or Auto-Negotiation NIC settings in Linux?

Date: November 20, 2008. Categories: debian, faq, fedora, howtos, linux, tips and ubuntu

Q: How to disable auto-negotiation option of my network interface card and set up half/full duplex mode manually from Linux command line (CLI)? By the way, how to see current settings?
A: There are several Linux utilities coming with almost any distribution including Debian, Ubuntu, Fedora, RedHat, Mandriva, Centos whatever. See details below.

auto-nego

ethtool

This is rather powerful utility can display and change settings of ethernet network interface card. You can easily disable/enable autonegotiation option for your NIC, also it’s possible to manually set up duplex mode, configure wake-on-lan options, set speed settings. Just look through full manual page for ethtool. Here are several ethtool usage examples:

ethtool eth0 - shows current NIC settings

Settings for eth0:
     Supported ports: [ TP MII ]
     Supported link modes:   10baseT/Half 10baseT/Full
                             100baseT/Half 100baseT/Full
     Supports auto-negotiation: Yes
     Advertised link modes:  10baseT/Half 10baseT/Full
                             100baseT/Half 100baseT/Full
     Advertised auto-negotiation: No
     Speed: 10Mb/s
     Duplex: Half
     Port: MII
     PHYAD: 32
     Transceiver: internal
     Auto-negotiation: off
     Supports Wake-on: pumbg
     Wake-on: d
     Current message level: 0x00000007 (7)
     Link detected: yes

ethtool -s eth0 duplex half autoneg off - disables auto-negotiation, enables Half Duplex.
ethtool -s eth1 duplex full speed 1000 autoneg off - disables auto-negotiation, enables Falf Duplex and sets up Speed to 1000 Mb/s.

mii-tool

According to manual it allows to manipulate and see media-independent interface status. Let’s see examples:

bash-3.1# mii-tool eth0
eth0: negotiated 100baseTx-FD, link ok - shows 100 Mbps speed, Full Duplex, Auto-negotiation is on.
bash-3.1# mii-tool eth0 -F 10baseT-HD - enables 10 Mb/s Half Duplex connection.

Taken From: http://www.linuxscrew.com/2008/11/20/faq-how-to-change-duplex-andor-auto-negotiation-nic-settings-in-linux/