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When I ping localhost on my Windows XP system, the TTL value returned is 128 and it shows me that the default TTL value in the ping for my system is 128. Then when I ping google.com the returned TTL value is 45, and I assume it means that (128 - 45) / 2 hops are existed in my way to google. When I tracert google.com, it says that the packets goes for maximum 30 numbers of hops, but it reaches the destination.

Why does it happen? Is it any difference between the TTL value showed in ping and the TTL value of tracert ?!

Thanks in advance . . .

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2 Answers 2

up vote 2 down vote accepted

Why does it happen?

Some host in path filtering you traceroute

Is it any difference between the TTL value showed in ping and the TTL value of tracert ?!

no difference(ping ttl=55, tracepath ttl=back=55)... no host filtering trace

ping ya.ru
PING ya.ru (87.250.250.3) 56(84) bytes of data.
64 bytes from www.yandex.ru (87.250.250.3): icmp_seq=1 ttl=55 time=36.6 ms

 tracepath ya.ru

 ....................

 8:  l3-s550-s450.yandex.net (213.180.213.23)              97.070ms 
 9:  l3-s650-s550.yandex.net (213.180.213.29)              97.992ms 
10:  www.yandex.ru (77.88.21.3)                            91.306ms reached
     Resume: pmtu 1500 hops 10 back 55

Then when I ping google.com the returned TTL value is 45, and I assume it means that (128 - 45) / 2 hops are existed in my way to google.

No. Path = 64(default google.com ttl) - 45(ping ttl) = 19 hops

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thank you very much –  Saba Jamalian Oct 17 '10 at 14:49

Different operating systems send replies to pings with different TTL (it doesn't depend upon the TTL in the incoming ping). Common starting values include 64, 128 and 255. I.e., your words "it means that (128 - 45) / 2 hops exist in my way to google" are wrong. Assuming that they use regular linux systems, they send ICMP packets with TTL = 64, and thus there are only 19 hops.

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thank you very much. –  Saba Jamalian Oct 17 '10 at 14:49

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