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IP and Routing

The ip command is the core of the iproute2 toolkit and the standard tool for managing network interfaces, IP addresses, and routes on modern Linux systems. This article covers how to use the ip command for network configuration on CentOS / AlmaLinux / Rocky Linux.

ip addr — Managing IP Addresses

Section titled “ip addr — Managing IP Addresses”

Viewing IP Addresses for All Interfaces

Section titled “Viewing IP Addresses for All Interfaces”
List all network interfaces and their IP addresses
ip addr show

Short form:

Short form for viewing IP addresses
ip a

Viewing the IP Address of a Specific Interface

Section titled “Viewing the IP Address of a Specific Interface”
View IP information for ens33 only
ip addr show dev ens33

Showing Only IPv4 Addresses

Section titled “Showing Only IPv4 Addresses”
Filter to show only IPv4 information
ip -4 addr show

Showing Only IPv6 Addresses

Section titled “Showing Only IPv6 Addresses”
Filter to show only IPv6 information
ip -6 addr show

Temporarily Adding an IP Address

Section titled “Temporarily Adding an IP Address”
Add a temporary IP address to ens33
sudo ip addr add 192.168.1.200/24 dev ens33

An interface can have multiple IP addresses bound to it:

Add a second IP address
sudo ip addr add 192.168.1.201/24 dev ens33

Removing an IP Address

Section titled “Removing an IP Address”
Remove a temporarily added IP address
sudo ip addr del 192.168.1.200/24 dev ens33

ip link — Managing Network Interfaces

Section titled “ip link — Managing Network Interfaces”

Viewing the Status of All Interfaces

Section titled “Viewing the Status of All Interfaces”
List the link status of all network interfaces
ip link show

Short form:

Short form for viewing link status
ip l

Enabling/Disabling an Interface

Section titled “Enabling/Disabling an Interface”
Bring up the ens33 interface
sudo ip link set ens33 up
Bring down the ens33 interface
sudo ip link set ens33 down

Changing the MTU Value

Section titled “Changing the MTU Value”
Set the MTU of ens33 to 9000 (jumbo frames)
sudo ip link set ens33 mtu 9000

Viewing Interface Statistics

Section titled “Viewing Interface Statistics”
Show packet transmit/receive statistics for an interface
ip -s link show ens33

ip route — Route Management

Section titled “ip route — Route Management”

Viewing the Routing Table

Section titled “Viewing the Routing Table”
Show the current routing table
ip route show

Short form:

Short form for viewing the routing table
ip r

Example output:

default via 192.168.1.1 dev ens33 proto dhcp metric 100
192.168.1.0/24 dev ens33 proto kernel scope link src 192.168.1.100 metric 100
  • default via 192.168.1.1 — Default gateway
  • 192.168.1.0/24 dev ens33 — Directly connected network

Viewing the Route to a Specific Destination

Section titled “Viewing the Route to a Specific Destination”
Check which route is used to reach 8.8.8.8
ip route get 8.8.8.8

Configuring the Default Gateway

Section titled “Configuring the Default Gateway”

Temporarily Changing the Default Gateway

Section titled “Temporarily Changing the Default Gateway”
Remove the current default gateway
sudo ip route del default
Add a new default gateway
sudo ip route add default via 192.168.1.254 dev ens33

Permanently Setting the Default Gateway with nmcli

Section titled “Permanently Setting the Default Gateway with nmcli”
Permanently configure the default gateway
sudo nmcli connection modify ens33 ipv4.gateway 192.168.1.1
sudo nmcli connection up ens33

Adding Static Routes

Section titled “Adding Static Routes”

Temporarily Adding a Static Route

Section titled “Temporarily Adding a Static Route”
Add a static route to the 10.10.0.0/16 network
sudo ip route add 10.10.0.0/16 via 192.168.1.254 dev ens33
Add a route to a specific host
sudo ip route add 172.16.5.10/32 via 192.168.1.254

Removing a Static Route

Section titled “Removing a Static Route”
Remove a static route
sudo ip route del 10.10.0.0/16

Permanently Adding Static Routes with nmcli

Section titled “Permanently Adding Static Routes with nmcli”

Temporary routes are lost after a reboot. Use nmcli to make them persistent:

Add a permanent static route to a connection
sudo nmcli connection modify ens33 +ipv4.routes "10.10.0.0/16 192.168.1.254"

Adding multiple routes:

Add multiple permanent static routes
sudo nmcli connection modify ens33 \
  +ipv4.routes "10.10.0.0/16 192.168.1.254" \
  +ipv4.routes "172.16.0.0/12 192.168.1.253"

Apply the configuration:

Reactivate the connection to apply routes
sudo nmcli connection up ens33

Viewing Permanently Configured Routes

Section titled “Viewing Permanently Configured Routes”
View static routes configured in nmcli
nmcli connection show ens33 | grep ipv4.routes

Removing a Permanent Static Route

Section titled “Removing a Permanent Static Route”
Remove a permanent route
sudo nmcli connection modify ens33 -ipv4.routes "10.10.0.0/16 192.168.1.254"
sudo nmcli connection up ens33

ip Command vs. ifconfig Comparison

Section titled “ip Command vs. ifconfig Comparison”

ifconfig belongs to the net-tools package and is no longer installed by default on newer EL systems. The ip command is more powerful and is the recommended replacement.

Purposeifconfig (legacy)ip (modern)
View all interfacesifconfigip addr show
View a specific interfaceifconfig ens33ip addr show dev ens33
Add an IP addressifconfig ens33 192.168.1.100 netmask 255.255.255.0ip addr add 192.168.1.100/24 dev ens33
Bring up an interfaceifconfig ens33 upip link set ens33 up
Bring down an interfaceifconfig ens33 downip link set ens33 down
View the routing tableroute -nip route show
Add a default gatewayroute add default gw 192.168.1.1ip route add default via 192.168.1.1
View interface statisticsifconfig ens33ip -s link show ens33

If you still need ifconfig, you can install net-tools:

Install the net-tools package (provides ifconfig)
sudo dnf install net-tools

Practical Tips

Section titled “Practical Tips”

Output in JSON Format (convenient for script parsing)

Section titled “Output in JSON Format (convenient for script parsing)”
Output IP address information in JSON format
ip -j addr show ens33

Combined with jq for formatted output:

Pretty-print JSON output with jq
ip -j addr show ens33 | jq .

Brief Output Format

Section titled “Brief Output Format”
Show IP addresses in brief mode
ip -br addr show
Show link status in brief mode
ip -br link show

Monitoring Network Changes

Section titled “Monitoring Network Changes”
Monitor route changes in real time
ip monitor route
Monitor all network events in real time
ip monitor all

Viewing the ARP Neighbor Table

Section titled “Viewing the ARP Neighbor Table”
Show the ARP neighbor cache
ip neighbour show