我正在尝试为 VPC 中的少数 EC2 实例启用 NTP，首先是 ntpdate，因为我的服务器距离较远，我不希望它发生故障。
我遇到了“没有适合同步的服务器”错误：
bash-4.1$ sudo ntpdate -u 0.amazon.pool.ntp.org
2 Oct 16:21:05 ntpdate[20767]: no server suitable for synchronization found
SO 上已经有少量帖子涉及此错误，通常与防火墙规则相关。
眼下：
- 该实例在所有端口上都打开，包括进出（不仅仅是 UDP/123）。
- 网络 ACL 在所有端口（进出）上均打开
- DNS 已打开并且 0.amazon.pool.ntp.org 正在解析为实际地址。
- NAT 似乎正在运行，能够使用 wget 访问其他外部地址（也可以解析 0.amazon.pool.ntp.org）
显然，我不能让服务器永远处于打开状态，这只是试图诊断问题。我不知道还能打开什么。
以下是诊断跟踪：
2 Oct 16:25:06 ntpdate[20815]: ntpdate [email protected] Mon Mar 9 14:24:09 UTC 2015 (1)
Looking for host 0.amazon.pool.ntp.org and service ntp
host found : services.quadranet.com
transmit(198.55.111.50)
transmit(50.116.55.65)
transmit(108.61.194.85)
transmit(173.44.32.10)
transmit(198.55.111.50)
transmit(50.116.55.65)
transmit(108.61.194.85)
transmit(173.44.32.10)
transmit(198.55.111.50)
transmit(50.116.55.65)
transmit(108.61.194.85)
transmit(173.44.32.10)
transmit(198.55.111.50)
transmit(50.116.55.65)
transmit(108.61.194.85)
transmit(173.44.32.10)
transmit(198.55.111.50)
transmit(50.116.55.65)
transmit(108.61.194.85)
transmit(173.44.32.10)
198.55.111.50: Server dropped: no data
50.116.55.65: Server dropped: no data
108.61.194.85: Server dropped: no data
173.44.32.10: Server dropped: no data
server 198.55.111.50, port 123
stratum 0, precision 0, leap 00, trust 000
refid [198.55.111.50], delay 0.00000, dispersion 64.00000
transmitted 4, in filter 4
reference time: 00000000.00000000 Sun, Dec 31 1899 19:00:00.000
originate timestamp: 00000000.00000000 Sun, Dec 31 1899 19:00:00.000
transmit timestamp: d9b966a5.c841bbbb Fri, Oct 2 2015 16:25:09.782
filter delay: 0.00000 0.00000 0.00000 0.00000
0.00000 0.00000 0.00000 0.00000
filter offset: 0.000000 0.000000 0.000000 0.000000
0.000000 0.000000 0.000000 0.000000
delay 0.00000, dispersion 64.00000
offset 0.000000
server 50.116.55.65, port 123
stratum 0, precision 0, leap 00, trust 000
refid [50.116.55.65], delay 0.00000, dispersion 64.00000
transmitted 4, in filter 4
reference time: 00000000.00000000 Sun, Dec 31 1899 19:00:00.000
originate timestamp: 00000000.00000000 Sun, Dec 31 1899 19:00:00.000
transmit timestamp: d9b966a5.fb750a47 Fri, Oct 2 2015 16:25:09.982
filter delay: 0.00000 0.00000 0.00000 0.00000
0.00000 0.00000 0.00000 0.00000
filter offset: 0.000000 0.000000 0.000000 0.000000
0.000000 0.000000 0.000000 0.000000
delay 0.00000, dispersion 64.00000
offset 0.000000
server 108.61.194.85, port 123
stratum 0, precision 0, leap 00, trust 000
refid [108.61.194.85], delay 0.00000, dispersion 64.00000
transmitted 4, in filter 4
reference time: 00000000.00000000 Sun, Dec 31 1899 19:00:00.000
originate timestamp: 00000000.00000000 Sun, Dec 31 1899 19:00:00.000
transmit timestamp: d9b966a6.2ea83387 Fri, Oct 2 2015 16:25:10.182
filter delay: 0.00000 0.00000 0.00000 0.00000
0.00000 0.00000 0.00000 0.00000
filter offset: 0.000000 0.000000 0.000000 0.000000
0.000000 0.000000 0.000000 0.000000
delay 0.00000, dispersion 64.00000
offset 0.000000
server 173.44.32.10, port 123
stratum 0, precision 0, leap 00, trust 000
refid [173.44.32.10], delay 0.00000, dispersion 64.00000
transmitted 4, in filter 4
reference time: 00000000.00000000 Sun, Dec 31 1899 19:00:00.000
originate timestamp: 00000000.00000000 Sun, Dec 31 1899 19:00:00.000
transmit timestamp: d9b966a6.61db63f1 Fri, Oct 2 2015 16:25:10.382
filter delay: 0.00000 0.00000 0.00000 0.00000
0.00000 0.00000 0.00000 0.00000
filter offset: 0.000000 0.000000 0.000000 0.000000
0.000000 0.000000 0.000000 0.000000
delay 0.00000, dispersion 64.00000
offset 0.000000
2 Oct 16:25:11 ntpdate[20815]: no server suitable for synchronization found
请提出建议吗？