Mastering the Linux ‘route’ Command: View, Add, and Delete IP Routes

Introduction

The route utility manipulates the kernel IP routing table, allowing you to display current routes or modify them with add and del options. Adding a route via the command line is temporary; to make it persistent you can place the command in /etc/rc.local.

Installation

yum install net-tools

Basic Usage

route [-f] [-p] [Command [Destination] [mask Netmask] [Gateway] [metric Metric]] [if Interface]

-c

: show more information -n: do not resolve names -v: verbose output -F: display forwarding information -C: show route cache -f: flush all routes -p: make the route permanent when used with add Common sub‑commands: add: add a new route del: delete an existing route -net: destination is a network -host: destination is a host netmask: required when adding a network route gw: specify the gateway (must be reachable) metric: set the route’s distance (hop count)

Output Explanation

# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.209.2   0.0.0.0         UG    100    0      0   ens33
10.10.0.0       0.0.0.0         255.255.255.0   !     0      -      0   -
192.168.209.0   0.0.0.0         255.255.255.0   U     100    0      0   ens33

Column meanings:

Destination : target network or host

Gateway : gateway address or ‘*’ if none

Genmask : subnet mask (255.255.255.255 for host, 0.0.0.0 for default)

Flags : U (up), H (host), G (gateway), R (reinstate), D (dynamic), M (modified), A (addrconf), C (cache), ! (reject)

Metric : distance to the target (used by routing daemons)

Ref : reference count (unused in Linux kernel)

Use : number of lookups (helps identify cache hits/misses)

Iface : outgoing interface

Practical Examples

Query the routing table

# route -n

Add a static route

# route add -net 10.10.10.0 gw 192.168.209.2 netmask 255.255.255.0 dev ens33

After adding, re‑run route -n to verify the new entry.

Delete a route

# route del -net 10.10.10.0 gw 192.168.209.2 netmask 255.255.255.0 dev ens33

Again, use route -n to confirm removal.

Add a reject (blackhole) route and then delete it

# route add -net 10.10.10.0 netmask 255.255.255.0 reject
# route -n   # shows a ‘!’ flag for the reject entry
# route del -net 10.10.10.0 netmask 255.255.255.0 reject
# route -n   # reject entry is gone