pingの結果のTTLの値は、パケットが経由したノードの数の分だけ減ったものです。 したがって、tracerouteでネットワーク経路上のノードを数えて、その分の数字を足せば、ホストが返すTTLの初期値が得られます。 TTLの初期値 = pingのTTL + tracerouteの結果 たとえば、「www.nap-camp.com」の場合、 % ping www.nap-camp.com PING www.nap-camp.com (104.26.0.222): 56 data bytes 64 bytes from 104.26.0.222: icmp_seq=0 ttl=57 time=16.373 ms 64 bytes from 104.26.0.222: icmp_seq=1 ttl=57 time=32.292 ms % sudo traceroute -I www.nap-c
![pingのTTLとtracerouteによるOSの推定](https://cdn-ak-scissors.b.st-hatena.com/image/square/e5dd3400bf5f6f104732efa77d1e43d40e00fbd5/height=288;version=1;width=512/https%3A%2F%2Fres.cloudinary.com%2Fzenn%2Fimage%2Fupload%2Fs--mOgD3dFw--%2Fc_fit%252Cg_north_west%252Cl_text%3Anotosansjp-medium.otf_55%3Aping%2525E3%252581%2525AETTL%2525E3%252581%2525A8traceroute%2525E3%252581%2525AB%2525E3%252582%252588%2525E3%252582%25258BOS%2525E3%252581%2525AE%2525E6%25258E%2525A8%2525E5%2525AE%25259A%252Cw_1010%252Cx_90%252Cy_100%2Fg_south_west%252Cl_text%3Anotosansjp-medium.otf_37%3ATetsuya%252520Ohira%252520%25252F%252520%2525E5%2525A4%2525A7%2525E5%2525B9%2525B3%2525E5%252593%2525B2%2525E4%2525B9%25259F%252Cx_203%252Cy_121%2Fg_south_west%252Ch_90%252Cl_fetch%3AaHR0cHM6Ly9saDMuZ29vZ2xldXNlcmNvbnRlbnQuY29tL2EtL0FPaDE0R2hjLVdQbHdZbUxqQnpxS2NPZkppTzl5cWtLNTBaRUxGV3pxWnNyPXMyNTAtYw%3D%3D%252Cr_max%252Cw_90%252Cx_87%252Cy_95%2Fv1627283836%2Fdefault%2Fog-base-w1200-v2.png)