TRACEROUTE

[Ravi Pande]

What is TCP traceroute and how TCP traceroute works?

[Richard Burts · Accepted solution]

The basic approach of traceroute is to send some type of probe packet toward the destination and to manipulate the Time to Live so that the packet times out on its way to the destination. From the error messages as the probe times out you can find the path toward the destination. Some types of traceroute (Windows tracert for example) send ICMP packets as the probe. Other types of OS (Cisco IOS routers and switches for example) send UDP as the probe packet. The TCP traceroute sends TCP packets as the probe.

HTH

Rick

[Ravi Pande]

Thanks for your reply.

I want to ask in all cases the error message you get is "ICMP:TTL exceeded"?

[Richard Burts · Accepted solution]

ICMP TTL exceeded would not be what is displayed to the user running the traceroute. But that is the message that is received in the software as the probes make their way toward the destination.

HTH

Rick

[Ravi Pande]

Okay got it.Thank you so much.

So in all three methods(ICMP,UDP,TCP) the error message is same i.e ICMP TTL exceeded message(through which it comes to know the hop ip address) but the initial packet is diff in all 3 case. 

Am I right?

[Richard Burts]

What you say here is correct.

HTH

Rick

[Ravi Pande]

Thanks a lot.

All doubts got cleared.

[Richard Burts]

I am glad that my explanations were helpful. If all doubts got cleared then perhaps you might want to mark this question as answered.

HTH

Rick