I use DNS in kubernetes. and test result like:

core@core-1-86 ~ $ kubectl exec busybox -- nslookup kubernetes
Server:    10.100.0.10
Address 1: 10.100.0.10

Name:      kubernetes
Address 1: 10.100.0.1

And then I entried to busybox container, and ping kubernetes, like:

core@core-1-86 ~ $ kubectl exec -it busybox sh
/ # ping kubernetes
PING kubernetes (10.100.0.1): 56 data bytes
^C
--- kubernetes ping statistics ---
55 packets transmitted, 0 packets received, 100% packet loss
/ #

if I ping another ip , it ok!

/ # ping 10.12.1.85
PING 10.12.1.85 (10.12.1.85): 56 data bytes
64 bytes from 10.12.1.85: seq=0 ttl=63 time=0.262 ms
64 bytes from 10.12.1.85: seq=1 ttl=63 time=0.218 ms
^C
--- 10.12.1.85 ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max = 0.218/0.240/0.262 ms
/ #

who can help me and tell me why?