Route Computation - HP 7102dl - ProCurve Secure Router Configuration Manual

IP Routing—Configuring RIP, OSPF, BGP, and PBR
Configuring OSPF
15-38
All routers generate Type 1 LSAs, which they use to advertise their own links.
A Type 1 LSA includes:
the link ID—in a point-to-point link, the neighboring router's ID (typically
its loopback interface address); in a link to a network, the network IP
address
the type of link—point to point, stub network, transit network
link status
metric—the cost for crossing the link, usually based on inverse bandwidth
Other important LSAs are Type 3 LSAs, which include:
the IP address and subnet mask for a network or range of networks
cost of the link to the network or networks
An ABR summarizes the networks in an area and then advertises a link to that
range of networks in a Type 3 LSA. The ABR sends only the summary to routers
in a different area from that of the networks advertised in the LSA. Type 3
LSAs allow routers to generate inter-area routes. You can configure an ABR
to advertise a single link to the entire range of networks in an area. You can
alternatively configure the ABR to advertise only some of the networks in
the area.
The ABR automatically advertises the default network 0.0.0.0 0.0.0.0. Routers
in total stub areas receive only this Type 3 LSA, which they use to generate a
default route for all traffic outside their area.
Type 5 LSAs advertise connections to external networks and are not received
by routers in stub areas. Stub routers use their default route for external
traffic.

Route Computation

Routers use the information they receive from LSAs to assemble a topological
database of the AS (or, if configured, area). This database includes:
all routers in the AS or area
all networks in the AS or area
all links in the AS or area
the cost for all links
The topological database for all routers in an AS (or area) is the same.
Theoretically, any router could calculate a route to a destination for any
other router.