A stub network is a somewhat casual term describing a computer network, or part of an internetwork, with no knowledge of other networks, that will typically send much or all of its non-local traffic out via a single path, with the network aware only of a default route

Default route

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...

 to non-local destinations. As a practical analogy, think of an island which is connected to the rest of the world through a bridge and no other path is available either through air or sea. Continuing this analogy, the island might have more than one physical bridge to the mainland, but the set of bridges still represents only one logical path.

• An enterprise LAN that connects to the corporate network by only one router, or multiple default routers connected to the same logical upstream destination.
• A single LAN
  Local area network
  A local area network is a computer network that interconnects computers in a limited area such as a home, school, computer laboratory, or office building...
  
   which never carries packets between multiple routers connected to it. All traffic is to and/or from local hosts. The routers will only route packets into the LAN if it's destined for the LAN, and out from the LAN if it originated on the LAN.
• A person, or workgroup, who is connected to an ISP, by only one router, is a stub network with respect to the ISP. This stub network is part of the ISP's autonomous system
  Autonomous system (Internet)
  Within the Internet, an Autonomous System is a collection of connected Internet Protocol routing prefixes under the control of one or more network operators that presents a common, clearly defined routing policy to the Internet....
  
  , discussed below.
• An OSPF stub area is one which only has a default route to the rest of the OSPF routing domain
  Routing domain
  In computer networking, a routing domain is a collection of networked systems that operate common routing protocols and are under the control of a single administration...
  
  . Such an area may have more than one router, but these routers will only know about the default route to the outside.
• A stub autonomous system
  Autonomous system (Internet)
  Within the Internet, an Autonomous System is a collection of connected Internet Protocol routing prefixes under the control of one or more network operators that presents a common, clearly defined routing policy to the Internet....
  
  that is connected to only one other autonomous system, through which it gains access to the Internet. This is also called a stub AS, which characterize the great majority of AS connected to the Internet. as of June 30, 2007, there were 224622 routes seen by the APNIC router. These came from 25577 autonomous systems, of which only 74 were transit-only and 22272 were stub/origin-only. 3305 autonomous systems provided some level of transit.