??????????棬??????????????????????80???????????????????????
$ sudo /sbin/iptables -L -n
Chain INPUT (policy ACCEPT)
target prot opt source destination
REJECT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:80 reject-with(
icmp-port-unreachable
Chain FORWARD (policy ACCEPT)
target prot opt source destination
Chain OUTPUT (policy ACCEPT)
target prot opt source destination

??????????????￡???????????????????????????????????????????80????????????????

???????綹?????????????

???????????????????????????????????????????????????????????????????????????????????鰈???????л??????????????????????綹????????????????????????????????????????Щ??????????????????????????????????????

????DNS????

???????DNS?????????????????????????????????????????????棬DNS??????????????????????????????????????????????????DNS????????????????????????????????????DNS???????30???????????????DNS??????????????????????dig??nslookup????????????????????????????????????????????DNS?????????????????????????????綹??????????????????????????DNS????????????????IP????????????Щ?????????п?????????????????????????

????Ping??tracerouter??oute??netstat????????iptables????????????????鶴????????DNS???????????????????????????????￡????????й??????????????IP????????????????????DNS?????????????????Щ??????????IP??????????????????????????Ч????ping??traceroute???棬????????????ping?????????????????????????????????????????netstat??iptables???棬??????????????????ò???????????????????????????????????DNS????

????????????????????У?????????????????DNS??????????????????????????о????????????????-n??????????佫IP????????????????????????????????????????-n??????--????????????????--?????????????????IP?????

???????DNS?????????????????Щ??????????????????web????????????Щweb????????????????????????IP??????н?????????????????????????????????????ü????????????????????????????????????web???????????--??????????????????????web???????????????ЩIP?????????????????????????????????????

????????traceroute??????綹??????

?????????????????е????????????????????????????????????????????鵽???????????????????????????????????????????????????????????漰???????????￡???????????????????traceroute???????????????tracerout???????????????в??????????????????????????Ч????????????????Ч???????????綹???????????????traceroute??????????????豸?????????????????????????????????????????????????????????????????????????????綹??????????????????????traceroute??????????й????????????????????????????????

$ traceroute yahoo.cn
traceroute to yahoo.cn (202.165.102.205)?? 30 hops max?? 60 byte packets
1 64-142-56-169.static.sonic.net (64.142.56.169) 1.666 ms 2.351 ms 3.038 ms
2 2.ge-1-1-0.gw.sr.sonic.net (209.204.191.36) 1.241 ms 1.243 ms 1.229 ms
3 265.ge-7-1-0.gw.pao1.sonic.net (64.142.0.198) 3.388 ms 3.612 ms 3.592 ms
4 xe-1-0-6.ar1.pao1.us.nlayer.net (69.22.130.85) 6.464 ms 6.607 ms 6.642 ms
5 ae0-80g.cr1.pao1.us.nlayer.net (69.22.153.18) 3.320 ms 3.404 ms 3.496 ms
6 ae1-50g.cr1.sjc1.us.nlayer.net (69.22.143.165) 4.335 ms 3.955 ms 3.957 ms
7 ae1-40g.ar2.sjc1.us.nlayer.net (69.22.143.118) 8.748 ms 5.500 ms 7.657 ms
8 as4837.xe-4-0-2.ar2.sjc1.us.nlayer.net (69.22.153.146) 3.864 ms 3.863 ms 3.865 ms
9 219.158.30.177 (219.158.30.177) 275.648 ms 275.702 ms 275.687 ms
10 219.158.97.117 (219.158.97.117) 284.506 ms 284.552 ms 262.416 ms
11 219.158.97.93 (219.158.97.93) 263.538 ms 270.178 ms 270.121 ms
12 219.158.4.65 (219.158.4.65) 303.441 ms * 303.465 ms
13 202.96.12.190 (202.96.12.190) 306.968 ms 306.971 ms 307.052 ms
14 61.148.143.10 (61.148.143.10) 295.916 ms 295.780 ms 295.860 ms
...

?????????????й?????????????????????????????????????????????????????????????????IP????????219.158.30.177??????ζ????????????????????й????????????????????3????????275????