我正在运行 Ubuntu LTS 22.04，使用 Chrony 作为 NTP 服务器。我发现，即使 NTP 客户端和 NTP 服务器之间有频繁的 NTP 流量，ARP 请求仍然会非常频繁地来回发送。默认情况下，ARP 缓存会在 60 秒后过期。
这是一个错误吗？
09:32:28.116858 IP 10.68.1.2.123 > 10.68.1.1.123: NTPv4, Client, length 48
09:32:28.117032 IP 10.68.1.1.123 > 10.68.1.2.123: NTPv4, Server, length 48
09:32:30.117770 IP 10.68.1.2.123 > 10.68.1.1.123: NTPv4, Client, length 48
09:32:30.117936 IP 10.68.1.1.123 > 10.68.1.2.123: NTPv4, Server, length 48
09:32:33.116704 ARP, Request who-has 10.68.1.1 tell 10.68.1.2, length 46
09:32:33.116750 ARP, Reply 10.68.1.1 is-at 20:7c:14:a0:b9:a1, length 28
09:32:33.190181 ARP, Request who-has 10.68.1.2 tell 10.68.1.1, length 28
09:32:33.190327 ARP, Reply 10.68.1.2 is-at 00:90:e8:9d:aa:dc, length 46
09:32:46.117215 IP 10.68.1.2.123 > 10.68.1.1.123: NTPv4, Client, length 48
09:32:46.117470 IP 10.68.1.1.123 > 10.68.1.2.123: NTPv4, Server, length 48
09:32:48.117032 IP 10.68.1.2.123 > 10.68.1.1.123: NTPv4, Client, length 48
09:32:48.117277 IP 10.68.1.1.123 > 10.68.1.2.123: NTPv4, Server, length 48
09:33:04.116931 IP 10.68.1.2.123 > 10.68.1.1.123: NTPv4, Client, length 48
09:33:04.117104 IP 10.68.1.1.123 > 10.68.1.2.123: NTPv4, Server, length 48
09:33:06.116888 IP 10.68.1.2.123 > 10.68.1.1.123: NTPv4, Client, length 48
09:33:06.117144 IP 10.68.1.1.123 > 10.68.1.2.123: NTPv4, Server, length 48
09:33:09.286195 ARP, Request who-has 10.68.1.2 tell 10.68.1.1, length 28
09:33:09.286332 ARP, Reply 10.68.1.2 is-at 00:90:e8:9d:aa:dc, length 46
09:33:22.116699 IP 10.68.1.2.123 > 10.68.1.1.123: NTPv4, Client, length 48
09:33:22.116833 IP 10.68.1.1.123 > 10.68.1.2.123: NTPv4, Server, length 48
09:33:24.116869 IP 10.68.1.2.123 > 10.68.1.1.123: NTPv4, Client, length 48
09:33:24.117034 IP 10.68.1.1.123 > 10.68.1.2.123: NTPv4, Server, length 48
09:33:27.116688 ARP, Request who-has 10.68.1.1 tell 10.68.1.2, length 46
09:33:27.116751 ARP, Reply 10.68.1.1 is-at 20:7c:14:a0:b9:a1, length 28
09:33:40.116842 IP 10.68.1.2.123 > 10.68.1.1.123: NTPv4, Client, length 48
09:33:40.117011 IP 10.68.1.1.123 > 10.68.1.2.123: NTPv4, Server, length 48
09:33:42.116923 IP 10.68.1.2.123 > 10.68.1.1.123: NTPv4, Client, length 48
09:33:42.117089 IP 10.68.1.1.123 > 10.68.1.2.123: NTPv4, Server, length 48
09:33:45.126169 ARP, Request who-has 10.68.1.2 tell 10.68.1.1, length 28
09:33:45.126332 ARP, Reply 10.68.1.2 is-at 00:90:e8:9d:aa:dc, length 46
09:33:58.116928 IP 10.68.1.2.123 > 10.68.1.1.123: NTPv4, Client, length 48
09:33:58.117095 IP 10.68.1.1.123 > 10.68.1.2.123: NTPv4, Server, length 48
09:34:00.116873 IP 10.68.1.2.123 > 10.68.1.1.123: NTPv4, Client, length 48
09:34:00.117039 IP 10.68.1.1.123 > 10.68.1.2.123: NTPv4, Server, length 48
09:34:16.116895 IP 10.68.1.2.123 > 10.68.1.1.123: NTPv4, Client, length 48
09:34:16.117154 IP 10.68.1.1.123 > 10.68.1.2.123: NTPv4, Server, length 48
09:34:18.116863 IP 10.68.1.2.123 > 10.68.1.1.123: NTPv4, Client, length 48
09:34:18.117029 IP 10.68.1.1.123 > 10.68.1.2.123: NTPv4, Server, length 48
09:34:21.116733 ARP, Request who-has 10.68.1.1 tell 10.68.1.2, length 46
09:34:21.116768 ARP, Reply 10.68.1.1 is-at 20:7c:14:a0:b9:a1, length 28
09:34:21.222128 ARP, Request who-has 10.68.1.2 tell 10.68.1.1, length 28
09:34:21.222294 ARP, Reply 10.68.1.2 is-at 00:90:e8:9d:aa:dc, length 46
09:34:34.116899 IP 10.68.1.2.123 > 10.68.1.1.123: NTPv4, Client, length 48
09:34:34.117069 IP 10.68.1.1.123 > 10.68.1.2.123: NTPv4, Server, length 48
09:34:36.127025 IP 10.68.1.2.123 > 10.68.1.1.123: NTPv4, Client, length 48
09:34:36.127269 IP 10.68.1.1.123 > 10.68.1.2.123: NTPv4, Server, length 48
09:34:52.116889 IP 10.68.1.2.123 > 10.68.1.1.123: NTPv4, Client, length 48
09:34:52.117145 IP 10.68.1.1.123 > 10.68.1.2.123: NTPv4, Server, length 48
09:34:54.116943 IP 10.68.1.2.123 > 10.68.1.1.123: NTPv4, Client, length 48
09:34:54.117187 IP 10.68.1.1.123 > 10.68.1.2.123: NTPv4, Server, length 48
09:34:57.318148 ARP, Request who-has 10.68.1.2 tell 10.68.1.1, length 28
09:34:57.318299 ARP, Reply 10.68.1.2 is-at 00:90:e8:9d:aa:dc, length 46
09:35:10.116983 IP 10.68.1.2.123 > 10.68.1.1.123: NTPv4, Client, length 48
09:35:10.117159 IP 10.68.1.1.123 > 10.68.1.2.123: NTPv4, Server, length 48
09:35:12.116865 IP 10.68.1.2.123 > 10.68.1.1.123: NTPv4, Client, length 48
09:35:12.117031 IP 10.68.1.1.123 > 10.68.1.2.123: NTPv4, Server, length 48
09:35:15.116750 ARP, Request who-has 10.68.1.1 tell 10.68.1.2, length 46
09:35:15.116810 ARP, Reply 10.68.1.1 is-at 20:7c:14:a0:b9:a1, length 28
答案1
这是非常正常的并且不是一个错误。
ARP 表条目只能通过 ARP 数据包（ARP 回复或 ARP 请求）进行刷新或更新。免费ARPARP 是通过 ARP 消息（而不是 IP 数据包）来发送的，因此，即使条目使用频繁，需要通过 ARP 请求/回复进行更新，也会超时。