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Traceroute Command Question :)

I learned that 'traceroute' command is pretty useful for troubleshooting. The problem is that some devices ignore ICMP request and I get requested timed out message instead of time exceeded message. 


[traceroute result]

 1 (  1.516 ms  0.814 ms  0.755 ms

 2  * * *

 3 (  5.512 ms  2.718 ms  3.140 ms

 4 (  1.974 ms  2.186 ms  1.795 ms

 5 (  3.461 ms (  3.448 ms (  5.564 ms

 6 (  2.546 ms (  3.212 ms  2.912 ms

 7 (  37.417 ms  41.917 ms (  70.367 ms

 8  * * *

 9 (  35.229 ms  35.214 ms  32.921 ms

10 (  32.687 ms  32.940 ms  32.442 ms


1. If I get a requested timed out message for TTL=2 ICMP Request, how traceroute still works? The gateway router will forward the packet to the best path according to the routing table. If my gateway router forwards my TTL=2 ICMP Request (Should be 1 when the gateway forwards) and the next hop router ignores it, either traceroute stops or I should keep getting a requested timed out message generated by my ping.exe. How come I reached google within 10hops?    

2. When my PC sends TTL = 5(could be 4) ICMP request, following is the result. There should be 1IP, but I see three IPs. Can anyone explain to me what is going on? (  3.461 ms (  3.448 ms (  5.564 ms

3. How come there are three RTT times? (  1.974 ms  2.186 ms  1.795 ms

4. I think RTT must keep increasing. But it seems like it also decreases when you look at 4 and 5. Why did it decrease? 

5. So, did I reach google within 10hops or 8 hopes(10-2 requested timed out)? 



VIP Mentor


You usually find that this is a result of a firewall or router ACL negating a response to a traceroute, Mostly though you wont even be aware of all the routers your traceroute actually passes through, Due to something call ttl-propagation which can be and usually is disabled so you cannot see the ISP's internal network.




kind regards

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