网管常用的网络命令
来源: 服务器&系统管理 WEB服务器 | 作者: ITeduer | 发布: 2007-5-07 03:05
使用 netstat 显示连接统计
可以使用 netstat 命令显示协议统计信息和当前的 TCP/IP 连接。netstat -a 命令将显示所有连接，而 netstat -r 显示路由表和活动连接。netstat -e 命令将显示Ethernet 统计信息，而 netstat -s 显示每个协议的统计信息。如果使用 netstat -n，则不能将地址和端口号转换成名称。下面是 netstat 的输出示例：
C:\>netstat -e
Interface Statistics
Received Sent
Bytes 3995837940 47224622
Unicast packets 120099 131015
Non-unicast packets 7579544 3823
Discards 0 0
Errors 0 0
Unknown protocols 363054211
C:\>netstat -a
Active Connections
Proto Local Address Foreign Address State
TCP CORP1:1572 172.16.48.10:nbsession ESTABLISHED
TCP CORP1:1589 172.16.48.10:nbsession ESTABLISHED
TCP CORP1:1606 172.16.105.245:nbsession ESTABLISHED
TCP CORP1:1632 172.16.48.213:nbsession ESTABLISHED
TCP CORP1:1659 172.16.48.169:nbsession ESTABLISHED
TCP CORP1:1714 172.16.48.203:nbsession ESTABLISHED
TCP CORP1:1719 172.16.48.36:nbsession ESTABLISHED
TCP CORP1:1241 172.16.48.101:nbsession ESTABLISHED
UDP CORP1:1025 *:*
UDP CORP1:snmp *:*
UDP CORP1:nbname *:*
UDP CORP1:nbdatagram *:*
UDP CORP1:nbname *:*
UDP CORP1:nbdatagram *:*
C:\>netstat -s
IP Statistics
Packets Received = 5378528
Received Header Errors = 738854
Received Address Errors = 23150
Datagrams Forwarded = 0
Unknown Protocols Received = 0
Received Packets Discarded = 0
Received Packets Delivered = 4616524
Output Requests = 132702
Routing Discards = 157
Discarded Output Packets = 0
Output Packet No Route = 0
Reassembly Required = 0
Reassembly Successful = 0
Reassembly Failures =
Datagrams Successfully Fragmented = 0
Datagrams Failing Fragmentation = 0
Fragments Created = 0
ICMP Statistics
Received Sent
Messages 693 4
Errors 0 0
Destination Unreachable 685 0
Time Exceeded 0 0
Parameter Problems 0 0
Source Quenches 0 0
Redirects 0 0
Echoes 4 0
Echo Replies 0 4
Timestamps 0 0
Timestamp Replies 0 0
Address Masks 0 0
Address Mask Replies 0 0
TCP Statistics
Active Opens = 597
Passive Opens = 135
Failed Connection Attempts = 107
Reset Connections = 91
Current Connections = 8
Segments Received = 106770
Segments Sent = 118431
Segments Retransmitted = 461
UDP Statistics
Datagrams Received = 4157136
No Ports = 351928
Receive Errors = 2
Datagrams Sent = 13809
使用 tracert 跟踪网络连接
Tracert（跟踪路由）是路由跟踪实用程序，用于确定 IP 数据报访问目标所采取的路径。Tracert 命令用 IP 生存时间 (TTL) 字段和 ICMP 错误消息来确定从一个主机到网络上其他主机的路由。
Tracert 工作原理
通过向目标发送不同 IP 生存时间 (TTL) 值的“Internet 控制消息协议 (ICMP)”回应数据包，Tracert 诊断程序确定到目标所采取的路由。要求路径上的每个路由器在转发数据包之前至少将数据包上的 TTL 递减 1。数据包上的 TTL 减为 0 时，路由器应该将 “ICMP 已超时”的消息发回源系统。
Tracert 先发送 TTL 为 1 的回应数据包，并在随后的每次发送过程将 TTL 递增 1，直到目标响应或 TTL 达到最大值，从而确定路由。通过检查中间路由器发回的“ICMP 已超时”的消息确定路由。某些路由器不经询问直接丢弃 TTL 过期的数据包，这在Tracert 实用程序中看不到。
Tracert 命令按顺序打印出返回“ICMP 已超时”消息的路径中的近端路由器接口列表。如果使用 -d 选项，则Tracert 实用程序不在每个 IP 地址上查询 DNS。
在下例中，数据包必须通过两个路由器（10.0.0.1 和 192.168.0.1）才能到达主机172.16.0.99。主机的默认网关是 10.0.0.1，192.168.0.0 网络上的路由器的 IP 地 址是 192.168.0.1。
C:\>tracert 172.16.0.99 -d
Tracing route to 172.16.0.99 over a maximum of 30 hops
1 2s 3s 2s 10,0.0,1
2 75 ms 83 ms 88 ms 192.168.0.1
3 73 ms 79 ms 93 ms 172.16.0.99
Trace complete.