netstat-打印網絡連接,路由表,接口統計信息的工具,在平常工作也會經常遇到;
常用選項:
-i:查看網卡數據包收發情況(常用於查看是否有丟包、錯誤)
-s:對各種協議的統計信息
-r:查看路由表信息(也常用route -n)查看
用法示例一:查看網絡包收發情況,以確定是否存在丟包的情況(當網絡存在延遲的時候用)
[root@admin test]# netstat -i Kernel Interface table Iface MTU RX-OK RX-ERR RX-DRP RX-OVR TX-OK TX-ERR TX-DRP TX-OVR Flg docker0 1500 34954 0 0 0 39693 0 0 0 BMRU eth0 1500 14214045 0 0 0 12320299 0 0 0 BMRU lo 65536 438426 0 0 0 438426 0 0 0 LRU vethd0731cd 1500 271 0 0 0 345 0 0 0 BMRU
RX-OK:接收的總包數
RX-ERR:總錯誤數
RX-DRP:進入 Ring Buffer 後因其他原因(如內存不足)導致的丟包數
RX-OVR:Ring Buffer 溢出導致的丟包數
TX-OK等也是類似的
用法示例二:對各種協議的統計信息(常用於確認傳輸層和網絡層是否出現問題)
會對ip、icmp、tcp、udp協議的網絡包數據進行統計
[root@nginx ~]# netstat -s Tcp: 0 active connection openings 3 passive connection openings 22 failed connection attempts 0 connection resets received 0 connections established 64 segments received 51 segments sent out 8 segments retransmitted 0 bad segments received 0 resets sent ... TcpExt: 22 resets received for embryonic SYN_RECV sockets 2 TCP sockets finished time wait in fast timer 0 packet headers predicted 8 acknowledgments not containing data payload received TCPTimeouts: 13 TCPOFOQueue: 2 TCPSynRetrans: 8 TCPOrigDataSent: 5 TCPDelivered: 5 IpExt: ...
22次連接失敗重試(22 failed connection attempts)
8 次重傳(8 segments retransmitted)
11 次半連接重置(11 resets received for embryonic SYN_RECV sockets)
8 次 SYN 重傳(TCPSynRetrans)
13 次超時(TCPTimeouts)