In this case the ping command sent a request for

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the first thing that happens is that the host name we specified is resolved into an IP address. In this case the ping command sent a request for fs3.nebo-tech.com to my DNS server, my DNS server responded with an IP address for this host name, 10.0.0.3, and then we sent the same for ICMP echo request packets and we got our ICMP echo responses. Now, recall earlier I said that if you run the ping command on a Linux system it will ping continuously until you tell it to stop. If for some reason you need to emulate that same functionality on a Windows system you can. You just have to add the -t parameter to the ping command. For example, we could ping FS3
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continually by entering ping -t fs3.nebo-tech.com and notice that it just keeps on pinging over and over and over until I press Control + C to tell it to stop. Now before we move on to traceroute I do need to warn you that some operating systems by default will have their host-based firewall configured to ignore ICMP echo request packets. If this is the case and you try to ping that host it's going to look like it's downbecause it's not going to respond. Now you need to be very careful about making assumptions in this situation because your first assumption would probably be that host is down or we have a break in our network connection somewhere. Which is actually not the case it's just that the remote system's host firewall is ignoring all of the ping requests and that's why we're not getting a response. traceroute Command 6:32-11:39 Alright, so the next command we want to look at is the traceroute command. On Windows it's tracert.If you run this command on Linux it's actually spelled all the way out, traceroute, R-O-U-T-E. Now the traceroute command uses the same ICMP protocol that ping does but what it does is manipulate the TTL parameter over here. This TTL parameter is very important. Every time one of these packets crosses a router the TTL is automatically decremented by one, and that's done for a very good reason. If you think about it, with the internet, if we were to send out a ping packet and that ping packet couldn't find the host that it was actually supposed to reach, if we didn't have a time to live parameter that ping packet would continually circle the internet for years and years and years and years never actually finding the destination host that it was supposed to go to. By adding a TTL parameter and by decrementing that parameter, eventually a packet that gets lost and can't find its destination will be dropped. When the TTL reaches zero, the router says, "Ah, this packet's been floating around too long. We're just going to dump it." Well this TTL functionality is actually manipulated by the traceroute commandbecause whenever a router sees a packet whose TTL has hit zero, it drops it, and what it does then is send an error message back to the host that originally sent that packet, informing it, "Hey, I had to drop this packet because it was going nowhere." Well traceroute actually manipulates that functionality. What we do with traceroute is we specify a remote host that we want to ping such as www. nebo-tech.com.
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