Rename eth1 as eth0

Step #2: Rename eth0 as wan0

To rename eth0 as wan0, edit a file called 70-persistent-net.rules in /etc/udev/rules.d/ directory, enter:
# vi /etc/udev/rules.d/70-persistent-net.rules
The names of the Ethernet devices are listed in this file as follows:

# PCI device 0x14e4:0x1680 (tg3)

SUBSYSTEM=="net",
ACTION=="add",
DRIVERS=="?*",
ATTR{address}=="b8:ac:6f:65:31:e5",
ATTR{dev_id}=="0x0",
ATTR{type}=="1",
KERNEL=="eth*",
NAME="eth0"

Locate and identify the line with the NIC from step 1 (look for the MAC address). It may look like above. In this example, the interface eth0 will be renamed to wan0 (change NAME="eth0" to NAME="wan0"):

# PCI device 0x14e4:0x1680 (tg3)

SUBSYSTEM=="net",
ACTION=="add",
DRIVERS=="?*",
ATTR{address}=="b8:ac:6f:65:31:e5",
ATTR{dev_id}=="0x0",
ATTR{type}=="1",
KERNEL=="eth*",
NAME="wan0"

Save and close the file. Reboot the system to test changes:
# reboot