From NetBSD Wiki

Introduction

A default route, also known as the gateway of last resort, is the network route used by a router when no other known route exists for a given IP packet's destination address. All the packets for destinations not known by the router's routing table are sent to the default route. This route generally leads to another router, which treats the packet the same way: If the route is known, the packet will get forwarded to the known route. If not, the packet is forwarded to the default-route of that router which generally leads to another router. And so on. Each router traversal adds a one-hop distance to the route.

Execution

You can add default route with following command (as a user with root privileges):

# route add default AA.BB.CC.DD

where the A-D letters represent numbers of an IP address.

To delete default route type following:

# route delete default

To permanently add default route you need to edit the /etc/rc.conf file adding there following line

defaultroute=AA.BB.CC.DD

or add the IP to /etc/mygate

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