Ifconfig and IPtables Configuration - linux

Question

Would someone explain this below output of ifconfig command. This PC is using USB IP4 Internet connection.
For example: why there is, inet6 addr: fe80::5a2c:80ff:fe13:9263/64 Scope:Link, assigned /
active on eth1, and why loopback is active.
Am trying to configure IPtables with minimum connections as possible and minimize the risk of intrusion.
I did not find an answer to this question.
With many updates and upgrades to Ubuntu since 12.04.
-------------------------------------------------------------------------------------/
eth0 Link encap:Ethernet HWaddr 00:1e:33:c6:64:94
UP BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
eth1 Link encap:Ethernet HWaddr 58:2c:80:13:92:63
inet addr:192.168.1.100 Bcast:192.168.1.255 Mask:255.255.255.0
inet6 addr: fe80::5a2c:80ff:fe13:9263/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:5291 errors:0 dropped:0 overruns:0 frame:0
TX packets:4188 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:4658548 (4.6 MB) TX bytes:458475 (458.4 KB)
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:65536 Metric:1
RX packets:783 errors:0 dropped:0 overruns:0 frame:0
TX packets:783 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:75702 (75.7 KB) TX bytes:75702 (75.7 KB)
-------------------------------------------------------------------------------/
This commend return empty results: nmcli dev list iface eth0 | grep IP4
----------------------------------------------------------------------------/
This commend : nmcli dev list iface eth1 | grep IP4
returns,
IP4.ADDRESS1: ip = 192.168.1.100/24, gw = 192.168.1.1
IP4.DNS1: 192.168.1.1
IP4.DNS[2]: 8.8.8.8
------------------------------------------------------------------------------/
Uname -a: 3.13.0-35-generic #62-Ubuntu SMP Fri Aug 15 01:58:42 UTC 2014 x86_64 x86_64
x86_64 GNU/Linux

Answer 1

In the folder /etc/network you have the interfaces file, in which you can configure your Ethernet configuration. With something like this:
#Configure Loopback
auto lo
iface lo inet loopback
#The primary network interfaces
auto eth0
iface eth0 intet static
address X.X.X.X
netmask 255.255.255.0
gateway X.X.X.255
I hope this can help