explaination of ip address

[jareid]

Here is a question that i missed on the test.
I now know the answer is:
PING 127.0.0.1

But why is that the answer? How do we know 127.0.0.1 ??

Question:
You are unable to telnet to a router at address 203.125.12.1 from a workstation with the IP address 203.125.12.23. You suspect that there is a problem with your protocol stack. Which of the following actions is most likely to confirm your diagnosis?
ping 127.0.0.0
ping 203.125.12.1
telnet 127.0.0.1
ping 127.0.0.1
tracert 203.125.12.1

[Dione]

look at page 98 in our softcover book, that will help you! IP Troubleshooting

[jareid]

local loopback!
I acutally remembered remembered that one.

I guess Dan was right about not focusing on the questions and just grasp the concept.

Thanks

[orastreet]

There are 4 steps to trouble shooting -

Ping Loopback - this verifies that IP is working. Many people think pinging the NIC does this, which it does, but it does not ISOLATE the protocol stack. If you can't ping your local interface is it IP or is it the card? The only way to tell is by pinging the loopback address.

Ping your NIC - This verifies that the INTERNALS of your NIC are functioning and your protocol stack is working. It's possible that you could get a response from your NIC but the card be damaged on the outside, like the small little pins could be crushed or mangled from somone sticking a fork or something in your NIC. Some people make a loopback cable to test for this.

Ping Your Gateway - This tells you a lot - IP, your NIC, your cable, your switch or Hub and the interface on your router/gateway is at least functioning up to layer 3.

Ping an address on the Internet or in another network - I always use 205.152.0.8 it's a Bellsouth DNS server. If I can ping it but can't get to the Internet through my browswer by typing an address, then my DNS is not function or I'm not configured to point to one for name resolution.

[aguilera]

any more questions on local loops?