ip-route-add

Add a default route using gateway forwarding

$ sudo ip [[r|route]] [[a|add]] default via [gateway_ip]

$ sudo ip [[r|route]] [[a|add]] default dev [ethX]

$ sudo ip [[r|route]] [[a|add]] [destination_ip] via [gateway_ip] dev [ethX]

$ sudo ip [[r|route]] [[a|add]] [destination_ip] dev [ethX] [[t|table]] [ip_address]

ip route add TO PREFIX [from PREFIX] [via NAME] [dev STRING] [options...]

to PREFIX
    Destination prefix (IPv4/IPv6) to match

from PREFIX
    Source prefix for route matching

dev STRING
    Outgoing device name

via NAME
    Next-hop gateway address

src ADDRESS
    Source address for outgoing packets

metric NUMBER
    Route preference metric (lower is preferred)

mtu NUMBER
    MTU for path

window NUMBER
    TCP window clamping

rtt TIME
    Initial RTT estimate (e.g., 2s)

initcwnd NUMBER
    Initial congestion window

type TYPE
    unicast|local|blackhole|broadcast|multicast|prohibit|unreachable|throw|xresolve

scope SCOPE
    global|site|link|host

protocol PROTOCOL
    kernel|boot|static|ra|man|...

onlink
    Treat route as directly connected

table TABLE_ID
    Routing table ID or name (default main)

pref MEDIUM
    Preference level: low|medium|high

vrf NAME
    VRF device name

iif STRING
    Incoming interface for encapsulation

The ip route add command, part of the iproute2 suite, dynamically adds a route to the kernel's routing table, enabling control over packet forwarding. It replaces legacy route command with more flexible syntax supporting multiple tables, policy routing, and advanced metrics.

It specifies destinations (TO PREFIX), next hops (via), devices (dev), and attributes like metrics or scopes. Routes can be unicast, blackhole, or multipath. Essential for VPNs, multi-homed hosts, or traffic engineering.

Requires root privileges. Changes persist until reboot unless added to config files like /etc/network/interfaces or via systemd-networkd. Use ip route show to verify. Errors like 'RTNETLINK answers: Network is unreachable' indicate invalid nexthops.

Requires root (use sudo). Invalid routes can cause network outage. Multipath needs equal metric. IPv6 prefers ip -6. Persists only until reboot without persistence tools.

ip route add 192.168.1.0/24 via 192.168.0.1 dev eth0 metric 100
Adds route for subnet via gateway on eth0.

ip route add 10.0.0.0/24 nexthop via 192.168.1.1 dev eth1 weight 1 nexthop via 192.168.2.1 dev eth2 weight 1
Balances via two paths.

Introduced in iproute2 (1999) by Alexey Kuznetsov as modern replacement for net-tools 'route'. Enhanced in Linux 2.2+ for policy routing; iproute2 v6+ adds VRF/multipath support.

ip route del(8), ip route show(8), ip route get(8), route(8), ss(8)