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UdevdRenamedNetworkInterfaceEth0ToEm1

The release of Fedora 15 has changed the network device naming scheme from ethX to a physical location-based name for easy identification and use.

dmesg |grep -i network

[fedora@localhost ~]$ dmesg |grep -i network
[    1.920925] Initializing network drop monitor service
[   20.728565] udevd[418]: renamed network interface eth0 to em1
[fedora@localhost ~]$

Reference : http://fedoraproject.org/wiki/Features/ConsistentNetworkDeviceNaming

Benefit to Fedora

System Administrators can then use BIOS-provided names, which are consistent and not arbitrarily named, for their network ports. This eliminates the confusion that non-deterministic naming brings, and eliminates the use of hard-coded MAC address based port renaming which a) is racy and error-prone, and b) introduces state into an otherwise stateless system.

/etc/sysconfig/network-scripts

[root@localhost network-scripts]# cat ifcfg-em1 
UUID="8dbdb3dc-be3a-4c9c-a8d6-a07cacf84f9a"
NM_CONTROLLED="yes"
HWADDR="00:08:74:22:5C:61"
BOOTPROTO="dhcp"
DEVICE="em1"
ONBOOT="no"
[root@localhost network-scripts]# 

This change affects most desktop, notebook, and server-class systems.

ifconfig -a em1

[root@localhost ~]# ifconfig -a em1
em1: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        ether 00:08:74:22:5c:61  txqueuelen 1000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
        device interrupt 11  base 0x2c00

System Administrators may disable this feature by passing "biosdevname=0" on the kernel command line.