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When using traceroute on my mac to check the path to any website, the first line is always 3 stars.

imac:~ Jerome$ traceroute google.com
traceroute: Warning: google.com has multiple addresses; using 173.194.70.113
traceroute to google.com (173.194.70.113), 64 hops max, 52 byte packets
 1  * * *
 2  217-168-54-101.static.cablecom.ch (217.168.54.101)  9.515 ms  8.757 ms  10.104 ms
 3  172.31.208.73 (172.31.208.73)  14.512 ms  14.605 ms  14.264 ms
 4  ch-zrh01b-ra1-ae-1.aorta.net (84.116.134.142)  13.587 ms  12.892 ms  13.936 ms
 5  74.125.49.101 (74.125.49.101)  13.966 ms  14.850 ms  14.915 ms
 6  72.14.232.120 (72.14.232.120)  26.573 ms
    72.14.232.88 (72.14.232.88)  20.072 ms  19.758 ms
 7  72.14.236.68 (72.14.236.68)  26.913 ms
    72.14.236.20 (72.14.236.20)  26.825 ms
    72.14.239.62 (72.14.239.62)  25.381 ms
 8  209.85.254.118 (209.85.254.118)  22.240 ms  22.365 ms
    209.85.254.112 (209.85.254.112)  24.826 ms
 9  * * *
10  fa-in-f113.1e100.net (173.194.70.113)  25.715 ms  26.960 ms  25.191 ms

As far as I know, * means no answer from the router. How come I have stars at the very first line ?

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2 Answers 2

up vote 1 down vote accepted

traceroute works by sending a packet with a deliberately low TTL count. This count is decremented by each router it transits, when the count is zero the router discards the packet and should send a reply saying that the TTL has expired.

The three asterisks are because traceroute makes three attempts to get a response at a particular TTL setting.

If any router is configured not to reply in the case of TTL expiry, it still does normal routing of packets and subsequent packets with higher TTLs are still passed along as they should be.

The next packet sent by traceroute has an initial TTL one higher, enabling it to reach one router further along the chain and get that next router to send an expiry response. This is why one router that doesn't respond does not stop traceroute

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Most likely, your router is not responding with "TTL exceeded in transit" ICMP responses, likely because a firewall (built into it) is suppressing those responses. If you are the router administrator, check the firewall settings. Otherwise, ignore it.

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