服务器外网掉线问题?

shinyrose

服务器近来出现外网掉线,内网不掉的怪现象.ping某一IP,正常情况下ping的情况稳定,当外网掉线是,ping是如下的情况:
64 bytes from 218.17.220.81: icmp_seq=391 ttl=54 time=10.8 ms
64 bytes from 218.17.220.81: icmp_seq=391 ttl=54 time=11.0 ms (DUP!)
64 bytes from 218.17.220.81: icmp_seq=392 ttl=54 time=15.1 ms
64 bytes from 218.17.220.81: icmp_seq=392 ttl=54 time=15.2 ms (DUP!)
64 bytes from 218.17.220.81: icmp_seq=393 ttl=54 time=9.71 ms
64 bytes from 218.17.220.81: icmp_seq=393 ttl=54 time=9.80 ms (DUP!)
64 bytes from 218.17.220.81: icmp_seq=394 ttl=54 time=13.1 ms
64 bytes from 218.17.220.81: icmp_seq=394 ttl=54 time=13.2 ms (DUP!)
64 bytes from 218.17.220.81: icmp_seq=395 ttl=54 time=10.0 ms
64 bytes from 218.17.220.81: icmp_seq=395 ttl=54 time=10.1 ms (DUP!)
64 bytes from 218.17.220.81: icmp_seq=396 ttl=54 time=75.9 ms
64 bytes from 218.17.220.81: icmp_seq=396 ttl=54 time=76.0 ms (DUP!)
64 bytes from 218.17.220.81: icmp_seq=397 ttl=54 time=9.62 ms
64 bytes from 218.17.220.81: icmp_seq=397 ttl=54 time=9.71 ms (DUP!)
64 bytes from 218.17.220.81: icmp_seq=398 ttl=54 time=17.7 ms
64 bytes from 218.17.220.81: icmp_seq=398 ttl=54 time=17.8 ms (DUP!)
64 bytes from 218.17.220.81: icmp_seq=399 ttl=54 time=11.8 ms
64 bytes from 218.17.220.81: icmp_seq=399 ttl=54 time=11.8 ms (DUP!)
64 bytes from 218.17.220.81: icmp_seq=400 ttl=54 time=10.3 ms
64 bytes from 218.17.220.81: icmp_seq=400 ttl=54 time=10.4 ms (DUP!)
请问这个是什么问题?是受攻击吗?
知道的朋友帮帮偶,被这个问题困扰很久了.系统是Linux