TMS zl Management and Configuration Guide ST.1.1.100430

9-32
Routing
OSPF
an ASBR. Typically, OSPF would not permit the external routes to be distrib-
uted into the stub area. However, internal routers in an NSSA can receive
specially defined LSAs for external routes.
LSA Types
Routers within an area exchange LSAs Type 1 and 2 to synchronize their
databases. Routers can also transmit LSAs Type 3, 4, and 5 between areas
so that they can learn how to route inter-area traffic. Table 9-14 summaries
the different LSA types.
Table 9-14. LSA Types
LSA Type Contains Originated By Link State ID Flooded To
1—router link • All directly connected
links:
–status
–cost
Any router Router ID All other routers (or DRs) in the area
2—network Router ID of all routers in a
broadcast network
A DR DR ID All other routers in the area
3—summary
link
• Network or range of
networks in an area
• Cost for the link to the
network(s)
An ABR Network
address
• All ABRs
• All internal routers in transit and stub
areas that do not include the
advertised network
• Except for the default route LSA, not
sent to internal routers in total stub
areas
4—summary
network and
ASB link-state
• Link to an ASBR:
– Status
–Cost
An ABR ASBR ID • All ABRs
• All internal routers in transit areas
• Not sent to internal routers in stub
and total stub areas
5—summary
external links
• External network or
range of external
networks
• Cost for the link
• External 1 (E1) routes,
which include external
cost and the cost to the
ASBR
• External 2 (E2) routes,
which only include
external cost
An ASBR External
network
address
• All ABRs
• All internal routers in transit areas
• Not sent to internal routers in stub
and total stub areas