如果您使用“show log”在日志缓冲区中显示消息，那么您使用的是 IOS 或 IOS-XE。

在这两个 Cisco 操作系统中，都有一个默认的 syslog 缓冲区大小（以字节为单位）。碰巧您当前可以在该缓冲区中容纳 360 条消息。

您可以使用以下命令将日志缓冲区大小更改为更大：“logging buffered 15000000 debugging”；该命令将使您的日志缓冲区大约为 15MB，并且将接受调试级别或更高级别的日志消息。

警告更改日志缓冲区大小将刷新当前日志缓冲区。

该命令show log将始终显示交换机/路由器的完整日志。您的设备可能设置为默认日志缓冲区，即 4096 字节。

您可以在配置模式下使用logging buffered <bytes to log>. 我们通常logging buffered 96000在我们的交换机上使用，它将日志缓冲区增加到 96 kb，而不是默认的 4 kb。

一个小技巧：

如果您有一个非常大的日志，那么在您到达您认为重要的那一天之前查看几个月的日志可能会有点令人沮丧。示例日志：

Jan  7 12:40:45.008: %SEC-6-IPACCESSLOGS: list tty_acl denied 68.183.212.251 3 packets
Jan  7 12:55:10.842: %SEC-6-IPACCESSLOGS: list tty_acl denied 1.87.209.253 1 packet
Jan  7 12:55:58.399: %SEC-6-IPACCESSLOGS: list tty_acl denied 125.44.146.175 1 packet
Jan  7 13:04:21.719: %SEC-6-IPACCESSLOGS: list tty_acl denied 178.140.50.247 1 packet
Jan  7 13:23:34.442: %SEC-6-IPACCESSLOGS: list tty_acl denied 119.41.198.91 1 packet
Jan  7 13:29:19.840: %SEC-6-IPACCESSLOGS: list tty_acl denied 69.163.46.118 1 packet
Jan  7 20:43:45.009: %SEC-6-IPACCESSLOGS: list tty_acl denied 92.63.197.100 1 packet
Jan  7 20:43:50.703: %SEC-6-IPACCESSLOGS: list tty_acl denied 196.52.43.84 1 packet
Jan  7 20:44:57.212: %SEC-6-IPACCESSLOGS: list tty_acl denied 180.111.205.112 1 packet
Jan  7 23:43:45.007: %SEC-6-IPACCESSLOGS: list tty_acl denied 80.211.250.29 1 packet
Jan  7 23:58:45.007: %SEC-6-IPACCESSLOGS: list tty_acl denied 80.211.250.29 1 packet
Jan  8 00:11:01.690: %SEC-6-IPACCESSLOGS: list tty_acl denied 58.135.224.45 1 packet
Jan  8 00:13:10.442: %SEC-6-IPACCESSLOGS: list tty_acl denied 80.82.77.139 1 packet
Jan  8 00:16:23.057: %SEC-6-IPACCESSLOGS: list tty_acl denied 209.141.50.57 1 packet
Jan  8 00:18:10.346: %SEC-6-IPACCESSLOGS: list tty_acl denied 199.19.226.226 1 packet
Jan  8 00:19:24.851: %SEC-6-IPACCESSLOGS: list tty_acl denied 194.61.24.146 1 packet
Jan  8 00:19:49.434: %SEC-6-IPACCESSLOGS: list tty_acl denied 199.19.225.65 1 packet
Jan  8 00:20:06.519: %SEC-6-IPACCESSLOGS: list tty_acl denied 45.163.110.194 1 packet
Jan  8 00:24:45.007: %SEC-6-IPACCESSLOGS: list tty_acl denied 194.61.24.146 1 packet
Jan  8 00:25:45.007: %SEC-6-IPACCESSLOGS: list tty_acl denied 199.19.225.65 1 packet
Jan  8 00:26:59.579: %SEC-6-IPACCESSLOGS: list tty_acl denied 139.162.120.98 1 packet
Jan  8 00:28:24.743: %SEC-6-IPACCESSLOGS: list tty_acl denied 124.193.236.138 1 packet
Jan  8 00:29:45.007: %SEC-6-IPACCESSLOGS: list tty_acl denied 199.19.226.226 1 packet
Jan  8 00:30:45.007: %SEC-6-IPACCESSLOGS: list tty_acl denied 209.141.50.57 1 packet
Jan  8 00:34:45.008: %SEC-6-IPACCESSLOGS: list tty_acl denied 199.19.226.226 1 packet
Jan  8 00:34:45.008: %SEC-6-IPACCESSLOGS: list tty_acl denied 139.162.120.98 1 packet
Jan  8 00:37:04.391: %SEC-6-IPACCESSLOGS: list tty_acl denied 209.141.52.115 1 packet
Jan  8 11:10:56.272: %SEC-6-IPACCESSLOGS: list tty_acl denied 14.204.211.7 1 packet
Jan  8 11:14:30.578: %SEC-6-IPACCESSLOGS: list tty_acl denied 218.5.36.120 1 packet
Jan  8 11:14:45.007: %SEC-6-IPACCESSLOGS: list tty_acl denied 91.236.116.214 11 packets
Jan  8 23:40:45.009: %SEC-6-IPACCESSLOGS: list tty_acl denied 185.244.25.105 1 packet
Jan  8 23:40:45.009: %SEC-6-IPACCESSLOGS: list tty_acl denied 218.92.1.178 3 packets
Jan  8 23:45:45.011: %SEC-6-IPACCESSLOGS: list tty_acl denied 185.244.25.105 1 packet
Jan  9 00:02:45.009: %SEC-6-IPACCESSLOGS: list tty_acl denied 209.141.52.115 1 packet
Jan  9 00:04:46.291: %SEC-6-IPACCESSLOGS: list tty_acl denied 27.117.75.75 1 packet
Jan  9 00:12:41.502: %SEC-6-IPACCESSLOGS: list tty_acl denied 92.63.197.100 1 packet
Jan  9 00:19:50.913: %SEC-6-IPACCESSLOGS: list tty_acl denied 139.162.120.98 1 packet
Jan  9 00:22:53.205: %SEC-6-IPACCESSLOGS: list tty_acl denied 178.128.174.232 1 packet
Jan  9 00:28:45.009: %SEC-6-IPACCESSLOGS: list tty_acl denied 178.128.174.232 1 packet
Jan  9 00:30:20.289: %SEC-6-IPACCESSLOGS: list tty_acl denied 194.93.59.14 1 packet
Jan  9 00:31:45.008: %SEC-6-IPACCESSLOGS: list tty_acl denied 209.141.52.115 1 packet
Jan  9 00:33:45.010: %SEC-6-IPACCESSLOGS: list tty_acl denied 178.128.174.232 3 packets
Jan  9 00:34:07.804: %SEC-6-IPACCESSLOGS: list tty_acl denied 211.220.29.189 1 packet
Jan  9 00:38:45.009: %SEC-6-IPACCESSLOGS: list tty_acl denied 92.63.197.100 1 packet
Jan  9 00:39:45.008: %SEC-6-IPACCESSLOGS: list tty_acl denied 178.128.174.232 2 packets
Jan  9 00:46:04.106: %SEC-6-IPACCESSLOGS: list tty_acl denied 82.102.173.75 1 packet
Jan  9 00:47:52.789: %SEC-6-IPACCESSLOGS: list tty_acl denied 151.233.83.216 1 packet
Jan  9 00:48:45.009: %SEC-6-IPACCESSLOGS: list tty_acl denied 178.128.174.232 1 packet
Jan  9 00:52:36.753: %SEC-6-IPACCESSLOGS: list tty_acl denied 221.6.255.227 1 packet
Jan  9 00:52:45.008: %SEC-6-IPACCESSLOGS: list tty_acl denied 221.207.32.250 1 packet
Jan  9 21:26:58.936: %SEC-6-IPACCESSLOGS: list tty_acl denied 66.214.40.126 1 packet
Jan  9 21:28:39.250: %SEC-6-IPACCESSLOGS: list tty_acl denied 61.254.59.237 1 packet
Jan  9 21:29:18.579: %SEC-6-IPACCESSLOGS: list tty_acl denied 181.27.212.142 1 packet
Jan  9 21:35:13.229: %SEC-6-IPACCESSLOGS: list tty_acl denied 84.147.129.81 1 packet
Jan  9 21:45:57.942: %SEC-6-IPACCESSLOGS: list tty_acl denied 209.141.52.115 1 packet
Jan  9 21:46:25.840: %SEC-6-IPACCESSLOGS: list tty_acl denied 111.231.249.29 1 packet
Jan  9 21:46:55.313: %SEC-6-IPACCESSLOGS: list tty_acl denied 178.128.174.232 1 
packet
Jan  9 23:55:25.208: %SEC-6-IPACCESSLOGS: list tty_acl denied 93.147.252.146 1 packet
Jan  9 23:58:45.975: %SEC-6-IPACCESSLOGS: list tty_acl denied 80.211.37.146 1 packet
Jan 10 00:01:33.029: %SEC-6-IPACCESSLOGS: list tty_acl denied 67.207.82.249 1 packet
Jan 10 00:09:29.297: %SEC-6-IPACCESSLOGS: list tty_acl denied 193.234.3.34 1 packet
Jan 10 00:15:45.008: %SEC-6-IPACCESSLOGS: list tty_acl denied 80.211.37.146 1 packet
Jan 10 00:27:45.008: %SEC-6-IPACCESSLOGS: list tty_acl denied 80.211.37.146 1 packet
Jan 10 00:28:05.721: %SEC-6-IPACCESSLOGS: list tty_acl denied 96.67.109.131 1 packet
Jan 10 00:33:35.994: %SEC-6-IPACCESSLOGS: list tty_acl denied 139.59.1.183 1 packet
Jan 10 00:33:45.011: %SEC-6-IPACCESSLOGS: list tty_acl denied 80.211.37.146 1 packet
Jan 10 01:39:13.017: %SEC-6-IPACCESSLOGS: list tty_acl denied 188.187.52.223 1 packet
Jan 10 01:41:54.761: %SEC-6-IPACCESSLOGS: list tty_acl denied 139.162.120.98 1 packet
Jan 10 01:47:00.554: %SEC-6-IPACCESSLOGS: list tty_acl denied 188.142.151.6 1 packet
Jan 10 01:51:45.009: %SEC-6-IPACCESSLOGS: list tty_acl denied 80.211.37.146 1 packet
Jan 10 01:56:45.009: %SEC-6-IPACCESSLOGS: list tty_acl denied 80.211.37.146 1 packet

现在如果只想查看1月10日的日志，可以使用命令

show log | be Jan 10

这将产生：

Jan 10 00:01:33.029: %SEC-6-IPACCESSLOGS: list tty_acl denied 67.207.82.249 1 packet
Jan 10 00:09:29.297: %SEC-6-IPACCESSLOGS: list tty_acl denied 193.234.3.34 1 packet
Jan 10 00:15:45.008: %SEC-6-IPACCESSLOGS: list tty_acl denied 80.211.37.146 1 packet
Jan 10 00:27:45.008: %SEC-6-IPACCESSLOGS: list tty_acl denied 80.211.37.146 1 packet
Jan 10 00:28:05.721: %SEC-6-IPACCESSLOGS: list tty_acl denied 96.67.109.131 1 packet
Jan 10 00:33:35.994: %SEC-6-IPACCESSLOGS: list tty_acl denied 139.59.1.183 1 packet
Jan 10 00:33:45.011: %SEC-6-IPACCESSLOGS: list tty_acl denied 80.211.37.146 1 packet
Jan 10 01:39:13.017: %SEC-6-IPACCESSLOGS: list tty_acl denied 188.187.52.223 1 packet
Jan 10 01:41:54.761: %SEC-6-IPACCESSLOGS: list tty_acl denied 139.162.120.98 1 packet
Jan 10 01:47:00.554: %SEC-6-IPACCESSLOGS: list tty_acl denied 188.142.151.6 1 packet
Jan 10 01:51:45.009: %SEC-6-IPACCESSLOGS: list tty_acl denied 80.211.37.146 1 packet
Jan 10 01:56:45.009: %SEC-6-IPACCESSLOGS: list tty_acl denied 80.211.37.146 1 packet

在 Cisco Nexus 平台上，您可以使用该命令show log last 50查看最近 50 条日志条目。