Operation and MaintenanceLinux Operation and MaintenanceWhat is the netstat command? How to use netstat command?
The netstat command is used to display various network-related information, such as network connections, routing tables, interface status (Interface Statistics), masquerade connections, and multicast memberships (Multicast Memberships) Wait
1 Commonly used options:
-a: (all) displays all options, and does not display LISTEN related ones by default
-t: (tcp) Only display tcp related options
-u: (udp) Only display udp related options
-n: Display IP and port in numbers, can display all numbers Convert to numbers.
-l: List only the service status in Listen (monitoring)
-p: Display the name of the program that establishes the relevant link
-r: Display routing information, Routing table
-e: Display extended information, such as uid, etc.
-s: Statistics based on each protocol
-c: Execute the netstat at regular intervals Order.
-w: raw socket related
2 -tan displays all tcp ports
[root@centos7 ~]# netstat -ant
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address Foreign Address State
tcp 0 0 0.0.0.0:111 0.0.0.0:* LISTEN
tcp 0 0 192.168.122.1:53 0.0.0.0:* LISTEN
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN
tcp 0 0 127.0.0.1:631 0.0.0.0:* LISTEN
tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN
tcp 0 52 192.168.29.3:22 192.168.29.1:51029 ESTABLISHED
TCP 0 0 192.168.29.3:22 192.168.29.1:51180 Established
##tcp6 0 0 :::22 :::* LISTENtcp6 0 0 ::1:631 :::* LISTENtcp6 0 0 ::1:25 :::* 3 show all udp ports -uan##[root@centos7 ~]# netstat -anu
Active Internet connections (servers and established)Proto Recv-Q Send-Q Local Address Foreign Address State
udp 0 0 0.0.0.0:5353 0.0.0.0 :*
udp 0 0 0.0.0.0:47414 0.0.0.0:*
udp 0 0 192.168.122.1:53 0.0.0.0:*
udp 0 0 0.0 .0.0:67 0.0.0.0:*
4 Display all listening tcp ports -tnl
##[root@centos7 ~]# netstat -tnl
Active Internet connections (only servers)Proto Recv-Q Send-Q Local Address Foreign Address State
tcp 0 0 0.0 .0.0:111 0.0.0.0:* LISTENtcp 0 0 192.168.122.1:53 0.0.0.0:* LISTENtcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN tcp 0 0 127.0.0.1:631 0.0.0.0:* LISTENtcp 0 0 127.0.0.1:25 0.0.0.0:* LISTENtcp6 0 0 : ::111 :::* LISTENtcp6 0 0 :::22 :::* LISTENtcp6 0 0 ::1:631 :::* LISTENtcp6 0 0 ::1:25 :::* LISTEN 5 Display all listening udp ports-unl[root@centos7 ~]# netstat -unl
Active Internet connections (only servers)Proto Recv-Q Send-Q Local Address Foreign Address State
udp 0 0 0.0.0.0:5353 0.0.0.0:*udp 0 0 0.0.0.0:47414 0.0.0.0:*udp 0 0 0.0.0.0:20815 0.0. 0.0:*udp 0 0 192.168.122.1:53 0.0.0.0:*udp 0 0 0.0.0.0:67 0.0.0.0:*udp 0 0 0.0.0.0:68 0.0.0.0:*udp 0 0 0.0.0.0:68 0.0.0.0:*udp 0 0 0.0.0.0:9804 0.0.0.0:*udp6 0 0 :::12799 :::*udp6 0 0 :::37953 :::* 6 show routing table –rn[root@centos7 ~]# netstat -nr
Kernel IP routing tableDestination Gateway Genmask Flags MSS Window irtt Iface
0.0.0.0 192.168.29.1 0.0.0.0 UG 0 0 0 ens33192.168.29.0 0.0.0.0 255.255.255.0 U 0 0 0 ens33192.168. 122.0 0.0.0.0 255.255.255.0 U 0 0 0 virbr0[root@centos7 ~]# route -nKernel IP routing tableDestination Gateway Genmask Flags Metric Ref Use Iface0.0.0.0 192.168.29.1 0.0.0.0 UG 100 0 0 ens33192.168.29.0 0.0.0.0 255.255.255.0 U 100 0 0 ens33192.168. 122.0 0.0.0.0 255.255.255.0 U 0 0 0 virbr0 7 Display statistics for each protocol(1) Display all ports Statistics netstat -s[root@centos7 ~]# netstat -s
Ip:3808 total packets received
0 forwarded0 incoming packets discarded2444 incoming packets delivered2254 requests sent out32 outgoing packets dropped Icmp:676 ICMP messages received0 input ICMP message failed.ICMP input histogram:destination unreachable: 148
echo replies: 528
717 ICMP messages sent
0 ICMP messages failed
ICMP output histogram:
destination unreachable: 148
echo request: 569
[……]
（2）显示 TCP 端口的统计信息 netstat -st
[root@centos7 ~]# netstat -st
IcmpMsg:
InType0: 528
InType3: 148
OutType3: 148
OutType8: 569
Tcp:
0 active connections openings
2 passive connection openings
0 failed connection attempts
0 connection resets received
2 connections established
1637 segments received
1418 segments send out
0 segments retransmited
0 bad segments received.
0 resets sent
（3）显示 UDP 端口的统计信息 netstat -su
[root@centos7 ~]# netstat -su
IcmpMsg:
InType0: 528
InType3: 148
OutType3: 148
OutType8: 569
Udp:
0 packets received
140 packets to unknown port received.
0 packet receive errors
169 packets sent
0 receive buffer errors
0 send buffer errors
UdpLite:
IpExt:
InMcastPkts: 27
OutMcastPkts: 33
InBcastPkts: 766
InOctets: 410294
OutOctets: 432666
InMcastOctets: 4963
OutMcastOctets: 5444
InBcastOctets: 179503
InNoECTPkts: 3848
8 显示 PID 和进程名称 netstat -p
[root@centos7 ~]# netstat -p
Active Internet connections (w/o servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 52 centos7.3.local:ssh gateway:51029 ESTABLISHED 1552/sshd: root@pts
tcp 0 0 centos7.3.local:ssh gateway:51180 ESTABLISHED 1854/sshd: root@pts
Active UNIX domain sockets (w/o servers)
Proto RefCnt Flags Type State I-Node PID/Program name Path
unix 2 [ ] DGRAM 8520 1/systemd /run/systemd/notify
unix 2 [ ] DGRAM 8522 1/systemd /run/systemd/cgroups-agent
unix 5 [ ] DGRAM 8542 1/systemd /run/systemd/journal/socket
unix 28 [ ] DGRAM 8544 1/systemd /dev/log
unix 2 [ ] DGRAM 11419 1/systemd /run/systemd/shutdownd
unix 3 [ ] STREAM CONNECTED 23993 1276/ibus-x11
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