功能說明：Netstat用於顯示與IP、TCP、UDP和ICMP協議相關的統計數據，一般用於檢驗本機各端口的網絡連接情況。
語 法：netstat [-acCeFghilMnNoprstuvVwx][-A<網絡類型>][--ip]
補充說明：利用netstat指令可讓你得知整個Linux系統的網絡情況。
參 數：
-a或–all 顯示所有連線中的Socket。
-A<網絡類型>或–<網絡類型> 列出該網絡類型連線中的相關地址。
-c或–continuous 持續列出網絡狀態。
-C或–cache 顯示路由器配置的快取信息。
-e或–extend 顯示網絡其他相關信息。
-F或–fib 顯示FIB。
-g或–groups 顯示多重廣播功能群組組員名單。
-h或–help 在線幫助。
-i或–interfaces 顯示網絡界面信息表單。
-l或–listening 顯示監控中的服務器的Socket。
-M或–masquerade 顯示偽裝的網絡連線。
-n或–numeric 直接使用IP地址，而不通過域名服務器。
-N或–netlink或–symbolic 顯示網絡硬件外圍設備的符號連接名稱。
-o或–timers 顯示計時器。
-p或–programs 顯示正在使用Socket的程序識別碼和程序名稱。
-r或–route 顯示Routing Table。
-s或–statistice 顯示網絡工作信息統計表。
-t或–tcp 顯示TCP傳輸協議的連線狀況。
-u或–udp 顯示UDP傳輸協議的連線狀況。
-v或–verbose 顯示指令執行過程。
-V或–version 顯示版本信息。
-w或–raw 顯示RAW傳輸協議的連線狀況。
-x或–unix 此參數的效果和指定”-A unix”參數相同。
–ip或–inet 此參數的效果和指定”-A inet”參數相同
netstat 的一些常用選項
netstat -s
本選項能夠按照各個協議分別顯示其統計數據。如果我們的應用程序（如Web瀏覽器）運行速度比較慢，或者不能顯示Web頁之類的數據，那么我們就可以用本選項來查看一下所顯示的信息。我們需要仔細查看統計數據的各行，找到出錯的關鍵字，進而確定問題所在。
[root@SM155 proc]# netstat -s Ip: 8530928 total packets received 0 forwarded 0 incoming packets discarded 6972819 incoming packets delivered 8521573 requests sent out 1 fragments dropped after timeout 39629 reassemblies required 19667 packets reassembled ok 1 packet reassembles failed Icmp: 16023 ICMP messages received 175 input ICMP message failed. ICMP input histogram: destination unreachable: 4362 echo requests: 11661 19476 ICMP messages sent 0 ICMP messages failed ICMP output histogram: destination unreachable: 7815 echo replies: 11661 Tcp: 1651264 active connections openings 159526 passive connection openings 197 failed connection attempts 150104 connection resets received 31 connections established 6439010 segments received 6739834 segments send out 423 segments retransmited 0 bad segments received. 1649444 resets sent Udp: 135397 packets received 7341 packets to unknown port received. 0 packet receive errors 1762263 packets sent TcpExt: ArpFilter: 0 800 TCP sockets finished time wait in fast timer 300 time wait sockets recycled by time stamp 8850 delayed acks sent 1 delayed acks further delayed because of locked socket Quick ack mode was activated 12 times 552580 packets directly queued to recvmsg prequeue. 296789 packets directly received from prequeue 724223 packets header predicted 11117 packets header predicted and directly queued to user TCPPureAcks: 249691 TCPHPAcks: 1235152 TCPRenoRecovery: 0 TCPSackRecovery: 1 TCPSACKReneging: 0 TCPFACKReorder: 0 TCPSACKReorder: 0
netstat -e
本選項用於顯示關於以太網的統計數據。它列出的項目包括傳送的數據報的總字節數、錯誤數、刪除數、數據報的數量和廣播的數量。這些統計數據既有發送的數據報數量，也有接收的數據報數量。這個選項可以用來統計一些基本的網絡流量）。
[root@SM155 proc]# netstat -e Active Internet connections (w/o servers) Proto Recv-Q Send-Q Local Address Foreign Address State User Inode tcp 0 0 10.90.243.155:49182 10.90.243.27:32931 ESTABLISHED root 382858 tcp 0 0 localhost.localdomain:49176 localhost.localdomain:39918 ESTABLISHED root 24542 tcp 1 0 10.90.243.155:64766 10.90.243.27:951 CLOSE_WAIT root 3239351 tcp 0 0 localhost.localdomain:39015 localhost.localdomain:49178 ESTABLISHED root 24546 tcp 0 0 localhost.localdomain:39016 localhost.localdomain:49179 ESTABLISHED root 24548 tcp 0 0 10.90.243.155:ssh 10.88.22.243:3672 ESTABLISHED root 6062002
netstat -r
本選項可以顯示關於路由表的信息，類似於后面所講使用route print命令時看到的 信息。除了顯示有效路由外，還顯示當前有效的連接。
[root@SM155 proc]# netstat -r Kernel IP routing table Destination Gateway Genmask Flags MSS Window irtt Iface 10.90.243.0 * 255.255.255.0 U 0 0 0 eth0 10.10.10.0 * 255.255.255.0 U 0 0 0 eth1 169.254.0.0 * 255.255.0.0 U 0 0 0 eth1 default 10.90.243.1 0.0.0.0 UG 0 0 0 eth0 [root@SM155 proc]#
netstat -a
本選項顯示一個所有的有效連接信息列表，包括已建立的連接（ESTABLISHED），也包括監聽連接請（LISTENING）的那些連接。
[root@SM155 proc]# netstat -a Active Internet connections (servers and established) Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 10.90.243.155:39010 *:* LISTEN tcp 0 0 *:shell *:* LISTEN tcp 0 0 10.90.243.155:39011 *:* LISTEN tcp 0 0 *:39012 *:* LISTEN tcp 0 0 *:39015 *:* LISTEN tcp 0 0 *:49159 *:* LISTEN tcp 0 0 localhost.localdomain:39016 *:* LISTEN tcp 0 0 *:49166 *:* LISTEN tcp 0 0 *:39918 *:* LISTEN tcp 0 0 *:sunrpc *:* LISTEN tcp 0 0 *:49173 *:* LISTEN tcp 0 0 *:ftp *:* LISTEN tcp 0 0 *:ssh *:* LISTEN tcp 0 0 *:13819 *:* LISTEN tcp 0 0 *:2812 *:* LISTEN tcp 0 0 10.90.243.155:49182 *:* LISTEN tcp 0 0 10.90.243.155:49182 10.90.243.27:32931 ESTABLISHED tcp 0 0 localhost.localdomain:49176 localhost.localdomain:39918 ESTABLISHED tcp 1 0 10.90.243.155:64766 10.90.243.27:951 CLOSE_WAIT tcp 0 0 localhost.localdomain:39015 localhost.localdomain:49178 ESTABLISHED tcp 0 0 localhost.localdomain:39016 localhost.localdomain:49179 ESTABLISHED
netstat -n
顯示所有已建立的有效連接。
[root@SM155 proc]# netstat -n Active Internet connections (w/o servers) Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 10.90.243.155:49182 10.90.243.27:32931 ESTABLISHED tcp 0 0 127.0.0.1:49176 127.0.0.1:39918 ESTABLISHED tcp 1 0 10.90.243.155:64766 10.90.243.27:951 CLOSE_WAIT tcp 0 0 127.0.0.1:39015 127.0.0.1:49178 ESTABLISHED tcp 0 0 127.0.0.1:39016 127.0.0.1:49179 ESTABLISHED tcp 0 0 127.0.0.1:39918 127.0.0.1:49176 ESTABLISHED tcp 0 0 10.90.243.155:58692 10.90.243.155:39010 ESTABLISHED tcp 0 0 10.90.243.155:39012 10.90.243.155:49168 ESTABLISHED tcp 0 0 127.0.0.1:39012 127.0.0.1:49174 ESTABLISHED tcp 0 0 10.90.243.155:39012 10.90.243.155:49175 ESTABLISHED tcp 0 0 127.0.0.1:39012 127.0.0.1:49160 ESTABLISHED tcp 0 0 10.90.243.155:39012 10.90.243.155:49161 ESTABLISHED tcp 0 0 127.0.0.1:39012 127.0.0.1:49167 ESTABLISHED tcp 0 0 10.90.243.155:49185 10.90.243.155:39011 ESTABLISHED tcp 0 0 127.0.0.1:49174 127.0.0.1:39012 ESTABLISHED tcp 0 0 10.90.243.155:49175 10.90.243.155:39012 ESTABLISHED tcp 0 0 10.90.243.155:49168 10.90.243.155:39012 ESTABLISHED tcp 0 0 127.0.0.1:49167 127.0.0.1:39012 ESTABLISHED tcp 0 0 127.0.0.1:49160 127.0.0.1:39012 ESTABLISHED tcp 0 0 10.90.243.155:49161 10.90.243.155:39012 ESTABLISHED tcp 0 0 10.90.243.155:49159 10.90.243.155:58726 ESTABLISHED tcp 0 0 127.0.0.1:49178 127.0.0.1:39015 ESTABLISHED