Operation and Maintenance
Linux Operation and Maintenance
What is the netstat command? How to use netstat command?
What 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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