[gregp@localhost ~]$ ifconfig eth0
eth0      Link encap:Ethernet  HWaddr 00:0C:29:E3:18:AA
          inet addr:10.10.10.1  Bcast:10.10.10.255  Mask:255.255.255.0
          inet6 addr: fe80::20c:29ff:fee3:18aa/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:1014 errors:0 dropped:0 overruns:0 frame:0
          TX packets:115 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:86035 (84.0 KiB)  TX bytes:9645 (9.4 KiB)
          Interrupt:185 Base address:0x1400

[gregp@localhost ~]$ ifconfig lo
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:16436  Metric:1
          RX packets:7327 errors:0 dropped:0 overruns:0 frame:0
          TX packets:7327 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:4802046 (4.5 MiB)  TX bytes:4802046 (4.5 MiB)

[gregp@localhost ~]$ ping -c 1 10.10.10.1
PING 10.10.10.1 (10.10.10.1) 56(84) bytes of data.
64 bytes from 10.10.10.1: icmp_seq=0 ttl=64 time=0.041 ms

--- 10.10.10.1 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.041/0.041/0.041/0.000 ms, pipe 2
[gregp@localhost ~]$ sudo ifconfig lo down
[gregp@localhost ~]$ ping -c 1 10.10.10.1
PING 10.10.10.1 (10.10.10.1) 56(84) bytes of data.

--- 10.10.10.1 ping statistics ---
1 packets transmitted, 0 received, 100% packet loss, time 0ms

[gregp@localhost ~]$