Just to prove a point, I booted my 486 running Slackware and pinged the 2 IPs it's assigned (127.0.0.1, 66.92.42.219) after yanking the NIC out of the system AFTER it was booted. The results?
PING 66.92.42.219 (66.92.42.219): 56 octets data
64 octets from 66.92.42.219: icmp_seq=0 ttl=255 time=1.1 ms
64 octets from 66.92.42.219: icmp_seq=1 ttl=255 time=0.9 ms
64 octets from 66.92.42.219: icmp_seq=2 ttl=255 time=0.9 ms
64 octets from 66.92.42.219: icmp_seq=3 ttl=255 time=0.9 ms
64 octets from 66.92.42.219: icmp_seq=4 ttl=255 time=0.9 ms
64 octets from 66.92.42.219: icmp_seq=5 ttl=255 time=0.9 ms
64 octets from 66.92.42.219: icmp_seq=6 ttl=255 time=0.9 ms
64 octets from 66.92.42.219: icmp_seq=7 ttl=255 time=0.9 ms
64 octets from 66.92.42.219: icmp_seq=8 ttl=255 time=0.9 ms
64 octets from 66.92.42.219: icmp_seq=9 ttl=255 time=0.9 ms
--- 66.92.42.219 ping statistics ---
10 packets transmitted, 10 packets received, 0% packet loss
round-trip min/avg/max = 0.9/0.9/1.1 ms
PING 127.0.0.1 (127.0.0.1): 56 octets data
64 octets from 127.0.0.1: icmp_seq=0 ttl=255 time=1.1 ms
64 octets from 127.0.0.1: icmp_seq=1 ttl=255 time=0.9 ms
64 octets from 127.0.0.1: icmp_seq=2 ttl=255 time=0.9 ms
64 octets from 127.0.0.1: icmp_seq=3 ttl=255 time=1.0 ms
64 octets from 127.0.0.1: icmp_seq=4 ttl=255 time=0.9 ms
64 octets from 127.0.0.1: icmp_seq=5 ttl=255 time=0.8 ms
64 octets from 127.0.0.1: icmp_seq=6 ttl=255 time=0.9 ms
64 octets from 127.0.0.1: icmp_seq=7 ttl=255 time=0.9 ms
64 octets from 127.0.0.1: icmp_seq=8 ttl=255 time=0.9 ms
64 octets from 127.0.0.1: icmp_seq=9 ttl=255 time=0.9 ms
--- 127.0.0.1 ping statistics ---
10 packets transmitted, 10 packets received, 0% packet loss
round-trip min/avg/max = 0.8/0.9/1.1 ms
Your NIC doesn't have a networking stack of any sort. It's not capable of responding to something like a ping. Your OS's IP stack will recognize when you're trying to ping yourself, and pass it through the loopback network interface instead. Pinging yourself to see if the NIC works does nothing but prove the TCP/IP stack can loopback. Just thought I'd point that out
-edit- The NIC is just a Joe Generic ISA NE2000 (Chipset is made by Atlantic).
eth0
Link encap:Ethernet HWaddr 00:20:35:16: D1:41
inet addr:66.92.42.219 Bcast:66.92.42.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:80 errors:225 dropped:6175 overruns:0 frame:12370
TX packets:136 errors:9 dropped:0 overruns:9 carrier:0
collisions:25 txqueuelen:100
RX bytes:5792 (5.6 Kb) TX bytes:10012 (9.7 Kb)
Interrupt:7 Base address:0x300