Routing Packets - 3Com CoreBuilder 2500 User Manual

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Routing Packets

OSPF
A packet's source and destination determine the routers that move it:
Intraarea — When a packet's source and destination are in the same
area, the packet is routed using internal router databases. No routers
are used outside the area.
Interarea — When a packet's source and destination are in different
areas, the topology databases in the backbone area dictate the paths
that are taken between areas.
You can use virtual links to influence the routes that are taken for
interarea traffic.
To a stub area — When a packet's destination is in a stub area (an
area that does not accept external route advertisements), OSPF uses
the area's predefined default route.
You configure default routing in area border routers that serve an OSPF
stub area, such as area border router 1 in Figure 7-1.
To a different autonomous system — When a packet's source and
destination are in different autonomous systems, autonomous system
boundary routers compute the routing paths using data obtained
from another protocol, such as the Border Gateway Protocol. The
boundary routers flood these external routes throughout the
autonomous system.
Boundary routers do not flood external routes into stub areas.