Published: Mon 24 April 2023
Updated: Fri 19 April 2024
By Don Cohoon
In linux .
tags: network
Network Management
The command line offers a wealth of network management commands. Here are some of my favorites.
nmcli
NetworkManager has a command line interface (CLI).
Get status:
$ nmcli general status
STATE CONNECTIVITY WIFI-HW WIFI WWAN-HW WWAN
connected full enabled enabled enabled enabled
Get connections:
$ nmcli connection show
NAME UUID TYPE DEVICE
Wired connection 1 39738cc4-2a3b-3990-8c49-b4d0355116c3 ethernet eth0
Get devices:
$ nmcli device
DEVICE TYPE STATE CONNECTION
eth0 ethernet connected Wired connection 1
usb0 ethernet unmanaged --
usb1 ethernet unmanaged --
lo loopback unmanaged --
Get configuration file names (notice they are in /etc and /run):
$ nmcli -f TYPE,FILENAME,NAME conn
TYPE FILENAME NAME
ethernet /etc/NetworkManager/system-connections/eno1.nmconnection eno1
loopback /run/NetworkManager/system-connections/lo.nmconnection lo
bridge /etc/NetworkManager/system-connections/virbr0.nmconnection virbr0
vlan /etc/NetworkManager/system-connections/vlan1.nmconnection vlan1
tun /run/NetworkManager/system-connections/vnet3.nmconnection vnet3
ethernet /etc/NetworkManager/system-connections/Wired connection 2 .nmconnection Wired connection 2
Show device details
$ nmcli device show eth0
GENERAL.DEVICE: eth0
GENERAL.TYPE: ethernet
GENERAL.HWADDR: 53 :21:B9:C6:B6:FE
GENERAL.MTU: 1500
GENERAL.STATE: 100 ( connected)
GENERAL.CONNECTION: Wired connection 1
GENERAL.CON-PATH: /org/freedesktop/NetworkManager/ActiveConnection/4
WIRED-PROPERTIES.CARRIER: on
IP4.ADDRESS[ 1 ] : 192 .168.1.9/24
IP4.GATEWAY: 192 .168.1.1
IP4.ROUTE[ 1 ] : dst = 0 .0.0.0/0, nh = 192 .168.1.1, mt = 100
IP4.ROUTE[ 2 ] : dst = 192 .168.10.0/24, nh = 0 .0.0.0, mt = 100
IP4.DNS[ 1 ] : 192 .168.10.1
IP6.ADDRESS[ 1 ] : fe80::cc1a:6ba2:c43:1b58/64
IP6.GATEWAY: --
IP6.ROUTE[ 1 ] : dst = fe80::/64, nh = ::, mt = 100
IP6.ROUTE[ 2 ] : dst = ff00::/8, nh = ::, mt = 256 , table = 255
Check the radio:
$ nmcli radio
WIFI-HW WIFI WWAN-HW WWAN
enabled enabled enabled enabled
Show available WiFi SSID signals:
$ nmcli device wifi list
SSID MODE CHAN RATE SIGNAL BARS SECURITY
MY_WIRELESS_NET Infra 11 54 Mbit/s 100 ▂▄▆█ WPA1 WPA2
ANOTHER_WIRELLESS_NET Infra 52 54 Mbit/s 100 ▂▄▆█ WPA1 WPA2
YET_ANOTHER_WIR_NET Infra 6 54 Mbit/s 55 ▂▄__ WPA2
Even get the WiFi password~
$ nmcli device wifi show-password
Connect to WiFi:
$ nmcli device wifi connect MY_WIRELESS_NET password 8ehdxhre5kkhb6g6
Device 'wlp5s0' successfully activated with 'a7c8fbf5-3e7d-456c-921b-d739de0e3c79' .
Reference: https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/networking_guide/sec-configuring_ip_networking_with_nmcli
ip
ip will show / manipulate routing, network devices, interfaces and tunnels
To show the IP addresses assigned to an interface on your server:
To assign an IP to an interface, for example, enps03:
# ip address add 192.168.1.254 / 24 dev enps03
To delete an IP on an interface:
# ip address del 192.168.1.254 / 24 dev enps03
Alter the status of the interface by bringing the interface eth0 online:
Alter the status of the interface by bringing the interface eth0 offline:
Alter the status of the interface by changing the MTU of eth0:
# ip link set eth0 mtu 9000
Alter the status of the interface by enabling promiscuous mode for eth0:
# ip link set eth0 promisc on
Add a default route (for all addresses) via the local gateway 192.168.1.254 that can be reached on device eth0:
# ip route add default via 192.168.1.254 dev eth0
Add a route to 192.168.1.0/24 via the gateway at 192.168.1.254:
# ip route add 192.168.1.0/24 via 192.168.1.254
Add a route to 192.168.1.0/24 that can be reached on device eth0:
# ip route add 192.168.1.0/24 dev eth0
Delete the route for 192.168.1.0/24 via the gateway at 192.168.1.254:
# ip route delete 192.168.1.0/24 via 192.168.1.254
Display the route taken for IP 10.10.1.4:
Reference:
ss
Show Socket program ss shows which ports are open, their status, and what programs are attached to them locally.
Sockets:
$ sudo ss -ntrp
State Recv-Q Send-Q Local Address:Port Peer Address:Port Process
...
Who is listening
$ sudo ss -lntup | less
Netid State Recv-Q Send-Q Local Address:Port Peer Address:PortProcess
...
Reference: https://www.man7.org/linux/man-pages/man8/ss.8.html
connmanctl
First found on the BeagleBoneBlack and PocketBeagle SBC devices, this was the way to manage WiFi, USB and Ethernet connections. It does not seem to be used on the BeagleBone AI [1].
The configuration files live in /var/lib/connman/ and the control program for changing them is connmanctl.
Here is an example run of connmanctl to set up a new WiFi connection [2] called MyWifi on an access point/router.
$ sudo connmanctl⏎
connmanctl> scan wifi⏎
Scan completed for wifi
connmanctl> services⏎
MyWifi wifi_1234567890_1234567890123456_managed_psk
connmanctl> agent on⏎
Agent registered
connmanctl> connect wifi_1234567890_1234567890123456_managed_psk⏎
Agent RequestInput wifi_1234567890_1234567890123456_managed_psk
Passphrase = [ Type = psk, Requirement = mandatory, Alternates =[ WPS ] ]
WPS = [ Type = wpspin, Requirement = alternate ]
Passphrase? MySecretPassphrase⏎
Connected wifi_1234567890_1234567890123456_managed_psk
connmanctl> quit⏎
$
Configure fixed IP address on wired ethernet port
Check settings before
$ sudo cat / var / lib / connman / ethernet_5051a9a6bafe_cable / settings
[ ethernet_5051a9a6bafe_cable ]
Name = Wired
AutoConnect = true
Modified = 2023 - 03 - 13 T22 : 49 : 38.241177 Z
IPv4 . method = manual
IPv4 . DHCP . LastAddress = 192.168.1.29
IPv6 . method = auto
IPv6 . privacy = disabled
IPv4 . netmask_prefixlen = 16
IPv4 . local_address = 192.168.1.99
IPv4 . gateway = 192.168.1.1
IPv6 . DHCP . DUID = 0001000126 b5d99b5051a9a6bafe
Change fixed IP address from 99 to 9
# ip address mask nameserver
$ sudo connmanctl config ethernet_5051a9a6bafe_cable ipv4 manual 192.168.1.9 255.255.0.0 192.168.1.1 ;
Check settings after
$ sudo cat / var / lib / connman / ethernet_5051a9a6bafe_cable / settings
[ ethernet_5051a9a6bafe_cable ]
Name = Wired
AutoConnect = true
Modified = 2023 - 03 - 13 T22 : 55 : 28.241177 Z
IPv4 . method = manual
IPv4 . DHCP . LastAddress = 192.168.1.29
IPv6 . method = auto
IPv6 . privacy = disabled
IPv4 . netmask_prefixlen = 16
IPv4 . local_address = 192.168.1.9
IPv4 . gateway = 192.168.1.1
IPv6 . DHCP . DUID = 0001000126 b5d99b5051a9a6bafe
You can see all the devices here, and turn on Tethering (incoming connections):
$ sudo cat / var / lib / connman / settings
[ global ]
OfflineMode = false
[ Wired ]
Enable = true
Tethering = false
[ WiFi ]
Enable = true
Tethering = false
[ Gadget ]
Enable = false
Tethering = false
[ P2P ]
Enable = false
Tethering = false
[ Bluetooth ]
Enable = true
Tethering = false
For wifi configuration, BeagleBone-AI-64, BeagleBonePlay (or later) moved from connman -> systemd-network, so wifi is now configured thru wpa_supplicant-wlan0.conf
You can use
Reference:
bbai-tether-system https://gist.github.com/kylemanna/6930087
firewalld
The Server Setup section of this book covers how to set up a firewall to protect your system network.
networkd
The Virtual IP Article covers networkd manipulation using netplan.
tcpdump
Here is a super useful program for tracing what is happening on your network.
For instance, you can watch a certain port for activity. In this example we watch port 81 (which is a web server).
$ sudo tcpdump - i eth0 - a port 81
tcpdump : verbose output suppressed , use - v [ v ] ... for full protocol decode
listening on eth0 , link - type EN10MB ( Ethernet ), snapshot length 262144 bytes
16 : 04 : 37.901252 IP 192.168.1.4.65088 > www . example . com .81 : Flags [ SEW ] , seq 1319586290 , win 65535 , options [ mss 1460,nop,wscale 6,nop,nop,TS val 582966262 ecr 0,sackOK,eol ] , length 0
16 : 04 : 37.901392 IP www . example . com .81 > 192.168.1.4.65088 : Flags [ S.E ] , seq 2476571858 , ack 1319586291 , win 65160 , options [ mss 1460,sackOK,TS val 1494679242 ecr 582966262,nop,wscale 7 ] , length 0
16 : 04 : 37.901630 IP 192.168.1.4.65088 > www . example . com .81 : Flags [ . ] , ack 1 , win 2058 , options [ nop,nop,TS val 582966264 ecr 1494679242 ] , length 0
16 : 04 : 37.904531 IP 192.168.1.4.65088 > www . example . com .81 : Flags [ P. ] , seq 1 : 638 , ack 1 , win 2058 , options [ nop,nop,TS val 582966267 ecr 1494679242 ] , length 637
16 : 04 : 37.904562 IP www . example . com .81 > 192.168.1.4.65088 : Flags [ . ] , ack 638 , win 505 , options [ nop,nop,TS val 1494679245 ecr 582966267 ] , length 0
16 : 04 : 37.905443 IP www . example . com .81 > 192.168.1.4.65088 : Flags [ P. ] , seq 1 : 257 , ack 638 , win 505 , options [ nop,nop,TS val 1494679246 ecr 582966267 ] , length 256
16 : 04 : 37.905634 IP 192.168.1.4.65088 > www . example . com .81 : Flags [ . ] , ack 257 , win 2054 , options [ nop,nop,TS val 582966268 ecr 1494679246 ] , length 0
16 : 04 : 37.906243 IP 192.168.1.4.65088 > www . example . com .81 : Flags [ P. ] , seq 638 : 718 , ack 257 , win 2054 , options [ nop,nop,TS val 582966268 ecr 1494679246 ] , length 80
16 : 04 : 37.906258 IP www . example . com .81 > 192.168.1.4.65088 : Flags [ . ] , ack 718 , win 505 , options [ nop,nop,TS val 1494679247 ecr 582966268 ] , length 0
16 : 04 : 37.906445 IP 192.168.1.4.65088 > www . example . com .81 : Flags [ . ] , seq 718 : 2166 , ack 257 , win 2054 , options [ nop,nop,TS val 582966268 ecr 1494679246 ] , length 1448
16 : 04 : 37.906465 IP www . example . com .81 > 192.168.1.4.65088 : Flags [ . ] , ack 2166 , win 501 , options [ nop,nop,TS val 1494679247 ecr 582966268 ] , length 0
16 : 04 : 37.906508 IP 192.168.1.4.65088 > www . example . com .81 : Flags [ P. ] , seq 2166 : 5653 , ack 257 , win 2054 , options [ nop,nop,TS val 582966268 ecr 1494679246 ] , length 3487
16 : 04 : 37.906532 IP www . example . com .81 > 192.168.1.4.65088 : Flags [ . ] , ack 5653 , win 480 , options [ nop,nop,TS val 1494679247 ecr 582966268 ] , length 0
16 : 04 : 37.906582 IP www . example . com .81 > 192.168.1.4.65088 : Flags [ P. ] , seq 257 : 528 , ack 5653 , win 480 , options [ nop,nop,TS val 1494679247 ecr 582966268 ] , length 271
16 : 04 : 37.906701 IP 192.168.1.4.65088 > www . example . com .81 : Flags [ . ] , ack 528 , win 2050 , options [ nop,nop,TS val 582966269 ecr 1494679247 ] , length 0
16 : 04 : 37.906871 IP www . example . com .81 > 192.168.1.4.65088 : Flags [ P. ] , seq 528 : 732 , ack 5653 , win 501 , options [ nop,nop,TS val 1494679248 ecr 582966269 ] , length 204
16 : 04 : 37.907007 IP 192.168.1.4.65088 > www . example . com .81 : Flags [ . ] , ack 732 , win 2047 , options [ nop,nop,TS val 582966269 ecr 1494679248 ] , length 0
^ C
17 packets captured
17 packets received by filter
0 packets dropped by kernel
arp-scan
arp-scan is a local network scanner capable of displaying known hosts by their IP address, MAC address, and manufacturer ID.
$ arp-scan --interface= eth0 192 .168.0.0/24
Interface: eth0, datalink type: EN10MB ( Ethernet)
Starting arp-scan 1 .4 with 256 hosts ( http://www.nta-monitor.com/tools/arp-scan/)
192 .168.0.1 00 :c0:9f:09:b8:db QUANTA COMPUTER, INC.
192 .168.0.3 00 :02:b3:bb:66:98 Intel Corporation
192 .168.0.5 00 :02:a5:90:c3:e6 Compaq Computer Corporation
192 .168.0.6 00 :c0:9f:0b:91:d1 QUANTA COMPUTER, INC.
192 .168.0.12 00 :02:b3:46:0d:4c Intel Corporation
192 .168.0.13 00 :02:a5:de:c2:17 Compaq Computer Corporation
192 .168.0.87 00 :0b:db:b2:fa:60 Dell ESG PCBA Test
192 .168.0.90 00 :02:b3:06:d7:9b Intel Corporation
192 .168.0.105 00 :13:72:09:ad:76 Dell Inc.
192 .168.0.153 00 :10:db:26:4d:52 Juniper Networks, Inc.
192 .168.0.191 00 :01:e6:57:8b:68 Hewlett-Packard Company
192 .168.0.251 00 :04:27:6a:5d:a1 Cisco Systems, Inc.
192 .168.0.196 00 :30:c1:5e:58:7d HEWLETT-PACKARD
13 packets received by filter, 0 packets dropped by kernel
Ending arp-scan: 256 hosts scanned in 3 .386 seconds ( 75 .61 hosts/sec) . 13
responded
Reference: https://linux.die.net/man/1/arp-scan
vnstat
To display the amount of network traffic for each day of the last week:
$ vnstat -d 7
eth01 / daily
day rx | tx | total | avg. rate
------------------------+-------------+-------------+---------------
2023 -04-16 9 .66 GiB | 3 .69 GiB | 13 .35 GiB | 1 .33 Mbit/s
2023 -04-17 13 .17 GiB | 6 .03 GiB | 19 .20 GiB | 1 .91 Mbit/s
2023 -04-18 11 .38 GiB | 5 .31 GiB | 16 .68 GiB | 1 .66 Mbit/s
2023 -04-19 14 .79 GiB | 5 .15 GiB | 19 .94 GiB | 1 .98 Mbit/s
2023 -04-20 12 .26 GiB | 2 .40 GiB | 14 .65 GiB | 1 .46 Mbit/s
2023 -04-21 14 .26 GiB | 3 .42 GiB | 17 .68 GiB | 1 .76 Mbit/s
2023 -04-22 12 .08 GiB | 1 .64 GiB | 13 .72 GiB | 1 .98 Mbit/s
------------------------+-------------+-------------+---------------
estimated 17 .57 GiB | 2 .39 GiB | 19 .96 GiB |
For the last two months:
$ vnstat
rx / tx / total / estimated
eth01:
2023 -03 334 .51 GiB / 94 .16 GiB / 428 .67 GiB
2023 -04 242 .84 GiB / 57 .62 GiB / 300 .47 GiB / 415 .63 GiB
yesterday 14 .26 GiB / 3 .42 GiB / 17 .68 GiB
today 12 .08 GiB / 1 .64 GiB / 13 .72 GiB / 19 .96 GiB
tun01:
2023 -03 0 B / 48 .57 KiB / 48 .57 KiB
2023 -04 0 B / 26 .12 KiB / 26 .12 KiB / --
yesterday 0 B / 1 .08 KiB / 1 .08 KiB
today 0 B / 816 B / 816 B / --
vlan101:
2023 -03 304 .72 GiB / 50 .54 GiB / 355 .26 GiB
2023 -04 220 .68 GiB / 25 .76 GiB / 246 .44 GiB / 340 .90 GiB
yesterday 13 .13 GiB / 1 .27 GiB / 14 .40 GiB
today 11 .28 GiB / 972 .62 MiB / 12 .23 GiB / 17 .79 GiB
wlp0s31e4:
2023 -03 0 B / 0 B / 0 B
2023 -04 0 B / 0 B / 0 B / --
yesterday 0 B / 0 B / 0 B
today 0 B / 0 B / 0 B / --
nethogs
To find out which program is demanding the most of your network right now, try nethogs.
NetHogs version 0.8.6 - 3
PID USER PROGRAM DEV SENT RECEIVED
828 monit / usr / bin / monit eth01 10.038 215.140 KB / sec
? root 192.168.1.3 : 40120 - 192.168.1.50 : 80 0.396 8.211 KB / sec
? root 192.168.1.3 : 40160 - 192.168.1.60 : 80 0.358 8.167 KB / sec
2925 www - da .. nginx : worker process eth01 2.048 1.875 KB / sec
1815892 root / usr / bin / docker - proxy docker 0.284 1.661 KB / sec
1815663 root python3 eth01 0.299 0.332 KB / sec
4287 bob sshd : bob @pts / 0 eth01 0.506 0.116 KB / sec
? root 192.168.1.4 : 40000 - 192.168.1.2 : 57392 0.000 0.000 KB / sec
? root 192.168.1.4 : 45308 - 192.168.1.5 : 80 0.000 0.000 KB / sec
TOTAL 13.929 235.501 KB / sec
Conclusion
This was a short list, hoping to provide an introduction to managing your network from the command line.
Hope this helps,