I found that I cannot ping 128.204.223.46, but I can ping 128.204.223.47
sss@sss-2 ~ % ping 128.204.223.46
PING 128.204.223.46 (128.204.223.46): 56 data bytes
Request timeout for icmp_seq 0
Request timeout for icmp_seq 1
Request timeout for icmp_seq 2
Request timeout for icmp_seq 3
Request timeout for icmp_seq 4
Request timeout for icmp_seq 5
Request timeout for icmp_seq 6
Request timeout for icmp_seq 7
C
--- 128.204.223.46 ping statistics ---
9 packets transmitted, 0 packets received, 100.0% packet loss
sss@sss-2 ~ % ping 128.204.223.47
PING 128.204.223.47 (128.204.223.47): 56 data bytes
64 bytes from 128.204.223.47: icmp_seq=0 ttl=112 time=281.044 ms
64 bytes from 128.204.223.47: icmp_seq=1 ttl=112 time=276.867 ms
64 bytes from 128.204.223.47: icmp_seq=2 ttl=112 time=361.150 ms
64 bytes from 128.204.223.47: icmp_seq=3 ttl=112 time=384.796 ms
64 bytes from 128.204.223.47: icmp_seq=4 ttl=112 time=302.729 ms
64 bytes from 128.204.223.47: icmp_seq=5 ttl=112 time=280.434 ms
64 bytes from 128.204.223.47: icmp_seq=6 ttl=112 time=345.877 ms
C
--- 128.204.223.47 ping statistics ---
7 packets transmitted, 7 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 276.867/318.985/384.796/41.051 ms