Ethernet

Ethernet is the low level stuff on top usually TCP/IP runs. Addressing on the Ethernet level uses the Media Access Control Address (MAC) and not the IP address. If the Ethernet packet is used for TCP/IP then it contains among other data a destination and a source IP address as regular data. It is the Ethernet protocol that sends the data from one physical device to an other not the IP protocol! It does this so well that it often can be ignored that an Ethernet protocol exist.

The Media Access Control Address (MAC) are 6 byte that should be unique for every Ethernet Interface (piece of Hardware). I used the word should since there are ways to modify the MAC address. TCP/IP and all network software assumes that those MAC addresses are unique and identify uniquely the computer. Some licensed software packages use this number to prevent from copying. There are different names for the MAC address ifconfig uses the term Hwaddr.

Example how to unload skge driver and add sky2:

rmmod skge

cd /etc/init.d

ln -s net.lo net.enp3s0

rc-update add net.enp3s0 default

/etc/init.d/net.enp3s0 stop

modprobe sky2

/etc/init.d/net.enp3s0 start

To see what you have ip a or ifconfig -a or ls /sys/class/net more than lo should be seen otherwise no matching kernel driver is loaded.

The new command ip will replace the no more maintained ifconfig that has some issues with new kernels. See man ip for the details.

To find out what driver is used type ethtool -i eth0

Note that udev gave the eth0 name to your network card, if you plug in and out network cards it happens that eth0 disappears but eth1 appears. This is probably not what you want, so check and delete the entries in /etc/udev/rules.d/70-persistent-net.rules.

# PCI device 0x1186:0x1300 (8139too)
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*",     ATTR{address}=="00:1e:58:3b:2d:f0", ATTR{type}=="1", KERNEL=="eth*", NAME="eth0"

This entry links the device driver (kernel module) 8139too, the MAC address 00:1e:58:3b:2d:f0 and the dev name eth0.

During startup of the net an IP address is assigned to a MAC address. This could be done in a fixed manner static IP address or by DHCP.


Linurs startpage