1. 抓包,抓包时过滤出dns服务的端口53即可。
2. 根据抓到的包查看dns服务器:
JVA82UGIGC9HVA8是一台连接在路由器下的电脑,192.168.100.1是电脑的网关及dns服务器,192.168.225.37是路由器的WAN接口地址,路由器的WAN接口已配置公用dns服务器8.8.8.8、114.114.114.114,192.168.225.1是路由器的上级。
15:56:16.777840 IP JVA82UGIGC9HVA8.lan.52705 > 192.168.100.1.53: 4510+ A? blog.sina.com.cn. (34)
15:56:16.777840 IP JVA82UGIGC9HVA8.lan.52705 > 192.168.100.1.53: 4510+ A? blog.sina.com.cn. (34)
15:56:16.778647 IP 192.168.225.37.23588 > 192.168.225.1.53: 13737+ A? blog.sina.com.cn. (34)
15:56:16.812663 IP 192.168.225.1.53 > 192.168.225.37.23588: 13737 2/0/0 CNAME blogx.sina.com.cn., A 123.126.45.92 (70)
15:56:16.813141 IP 192.168.100.1.53 > JVA82UGIGC9HVA8.lan.52705: 4510 2/0/0 CNAME blogx.sina.com.cn., A 123.126.45.92 (70)
15:56:16.813192 IP 192.168.100.1.53 > JVA82UGIGC9HVA8.lan.52705: 4510 2/0/0 CNAME blogx.sina.com.cn., A 123.126.45.92 (70)
这里可以看出解析出IP的dns服务器是192.168.225.1,53是其端口。
15:56:49.431590 IP JVA82UGIGC9HVA8.lan.60251 > 192.168.100.1.53: 56569+ A? www.booking.com. (33)
15:56:49.431590 IP JVA82UGIGC9HVA8.lan.60251 > 192.168.100.1.53: 56569+ A? www.booking.com. (33)
15:56:49.432969 IP 192.168.225.37.59478 > public1.114dns.com.53: 20018+ A? www.booking.com. (33)
15:56:49.464038 IP public1.114dns.com.53 > 192.168.225.37.59478: 20018 2/0/0 CNAME www.c.booking.com., A 185.28.220.2 (69)
15:56:49.464882 IP 192.168.100.1.53 > JVA82UGIGC9HVA8.lan.60251: 56569 2/0/0 CNAME www.c.booking.com., A 185.28.220.2 (69)
15:56:49.464944 IP 192.168.100.1.53 > JVA82UGIGC9HVA8.lan.60251: 56569 2/0/0 CNAME www.c.booking.com., A 185.28.220.2 (69)
这里可以看出解析出IP的dns服务器是public1.114dns.com(114.114.114.114),53是其端口。