A FreeBSD system can be configured as the default gateway, or router, for a network if it is a dual-homed system.
A dual-homed system is a host which resides on at least two different networks.
Typically, each network is connected to a separate network interface, though
IP aliasing can be used to bind multiple addresses, each on a different subnet, to one physical interface.
In order for the system to forward packets between interfaces, FreeBSD must be configured as a router.
Internet standards and good engineering practice prevent the FreeBSD Project from enabling this feature by default, but it can be configured to start at boot by adding this line to
gateway_enable="YES" # Set to YES if this host will be a gateway
To enable routing now, set the sysctl(8)
To stop routing, reset this variable to
The routing table of a router needs additional routes so it knows how to reach other networks.
Routes can be either added manually using static routes or routes can be automatically learned using a routing protocol.
Static routes are appropriate for small networks and this section describes how to add a static routing entry for a small network.
For large networks, static routes quickly become unscalable.
FreeBSD comes with the standard
BSD routing daemon routed(8)
, which provides the routing protocols
RIP, versions 1 and 2, and
Support for the
OSPF routing protocols can be installed using the net/zebra
package or port.
Consider the following network:
In this scenario,
is a FreeBSD machine that is acting as a router to the rest of the Internet.
It has a default route set to
which allows it to connect with the outside world.
is already configured to use
as its default gateway.
Before adding any static routes, the routing table on
looks like this:
% netstat -nrRouting tables
Destination Gateway Flags Refs Use Netif Expire
default 10.0.0.1 UGS 0 49378 xl0
127.0.0.1 127.0.0.1 UH 0 6 lo0
10.0.0.0/24 link#1 UC 0 0 xl0
192.168.1.0/24 link#2 UC 0 0 xl1
With the current routing table,
does not have a route to the
The following command adds the
2 network to
's routing table using
as the next hop:
# route add -net 192.168.2.0/24 192.168.1.2
can reach any host on the
However, the routing information will not persist if the FreeBSD system reboots.
If a static route needs to be persistent, add it to
# Add Internal Net 2 as a persistent static route
route_internalnet2="-net 192.168.2.0/24 192.168.1.2"
static_routes configuration variable is a list of strings separated by a space, where each string references a route name.
route_ contains the static route for that route name.
Using more than one string in
static_routes creates multiple static routes.
The following shows an example of adding static routes for the
route_net1="-net 192.168.0.0/24 192.168.0.1"
route_net2="-net 192.168.1.0/24 192.168.1.1"