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Beginner

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 google.com result]

 1  172.30.1.254 (172.30.1.254)  1.516 ms  0.814 ms  0.755 ms

 2  * * *

 3  112.188.8.9 (112.188.8.9)  5.512 ms  2.718 ms  3.140 ms

 4  112.188.2.69 (112.188.2.69)  1.974 ms  2.186 ms  1.795 ms

 5  112.174.58.93 (112.174.58.93)  3.461 ms

    112.174.58.109 (112.174.58.109)  3.448 ms

    112.174.58.117 (112.174.58.117)  5.564 ms

 6  112.174.11.106 (112.174.11.106)  2.546 ms

    112.174.7.2 (112.174.7.2)  3.212 ms  2.912 ms

 7  72.14.194.106 (72.14.194.106)  37.417 ms  41.917 ms

    72.14.194.194 (72.14.194.194)  70.367 ms

 8  * * *

 9  108.170.233.15 (108.170.233.15)  35.229 ms  35.214 ms  32.921 ms

10  nrt12s13-in-f206.1e100.net (172.217.25.206)  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? 

112.174.58.93 (112.174.58.93)  3.461 ms

112.174.58.109 (112.174.58.109)  3.448 ms

112.174.58.117 (112.174.58.117)  5.564 ms

3. How come there are three RTT times? 

112.188.2.69 (112.188.2.69)  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)? 

 

 

1 REPLY 1
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VIP Mentor

Hell0

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.

 

res

Paul



kind regards
Paul

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