Lesson 96: route Command
In this lesson, you'll learn how to use the route command to view, add, delete, and manage the IP routing table on your Linux system.
The route command reads and writes to the kernel's IP routing table a set of rules that the kernel consults for every outbound packet to decide which network interface and gateway to use.
When you type ping google.com, the kernel checks the routing table before the first packet is ever sent.
If no matching route exists, the packet is dropped immediately with a "Network is unreachable" error, never reaching the network at all.
Understanding and managing the routing table is a fundamental sysadmin skill for configuring multi-homed servers, setting up VPN routing, isolating traffic by interface, and diagnosing connectivity failures that ping and traceroute alone cannot explain.
route command is part of the legacy net-tools package. On modern Linux systems, it has been superseded by the ip route command from the iproute2 package, which is more powerful and consistent. Both are covered in this lesson
route for familiarity with older systems and documentation, ip route as the modern equivalent you should use going forward.Installation
sudo apt install net-tools # Debian/Ubuntu
Or:
sudo dnf install net-tools # Fedora/RHEL 9+
Syntax
route [OPTIONS]
route add [OPTIONS] TARGET
route del [OPTIONS] TARGET
Options
| Option | Description |
|---|---|
-n |
Show IP addresses numerically — skip DNS resolution |
-v |
Verbose output |
-e |
Display the routing table in netstat format |
-4 |
Show IPv4 routing table only |
-6 |
Show IPv6 routing table only |
add |
Add a new route |
del |
Delete an existing route |
-net |
Target is a network address |
-host |
Target is a host address |
gw |
Specify the gateway for the route |
metric |
Set the route priority (lower = preferred) |
dev |
Specify the network interface |
Understanding the Routing Table Output
route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
default gateway 0.0.0.0 UG 100 0 0 enp0s3
192.168.0.0 0.0.0.0 255.255.255.0 U 100 0 0 enp0s3
192.168.122.0 0.0.0.0 255.255.255.0 U 0 0 0 virbr0
Each row is a routing rule. Here is what every column means:
| Column | What It Means |
|---|---|
Destination |
The target network or host this rule applies to |
Gateway |
Where to send the packet next (0.0.0.0 means directly connected — no gateway needed) |
Genmask |
The subnet mask for the destination network |
Flags |
Route status flags (see table below) |
Metric |
Route priority — lower value is preferred when multiple routes match |
Ref |
Number of references to this route (legacy, usually 0) |
Use |
Number of times this route has been used |
Iface |
The network interface packets leave through |
Route flags:
| Flag | Meaning |
|---|---|
U |
Route is Up (active) |
G |
Route uses a Gateway |
H |
Target is a Host (not a network) |
R |
Route was reinstated dynamically |
D |
Route was created dynamically by a daemon |
M |
Route was modified by a routing daemon |
! |
Route is rejected (blocked) |
default route (also shown as 0.0.0.0 destination with 0.0.0.0 Genmask) is the gateway of last resort; all packets that don't match any more specific route are sent here. A missing default route means the system can only communicate with directly connected networks.
1. View the Kernel Routing Table
route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
default gateway 0.0.0.0 UG 100 0 0 enp0s3
192.168.0.0 0.0.0.0 255.255.255.0 U 100 0 0 enp0s3
192.168.122.0 0.0.0.0 255.255.255.0 U 0 0 0 virbr0
The three routes in this typical output tell you:
- default via gateway on enp0s3 — all non-local traffic goes to the ISP/router gateway
- 192.168.0.0/24 on enp0s3 — packets to this local network go directly out enp0s3 without a gateway
- 192.168.122.0/24 on virbr0 — traffic to the KVM virtual bridge network goes through the
virbr0interface