Information Technology Reference
In-Depth Information
Foundation Summary
The Foundation Summary is a condensed collection of material that provides a convenient
review of key concepts in this chapter. If you are already comfortable with the topics in this
chapter, this summary will help you recall a few details. If you just read the Foundation Topics
section, this review should help solidify some key facts. If you are doing your final preparation
before the exam, these materials are a convenient way to review the day before the exam.
OSPF Major LSA Types
Table 8-3
Type Code
Type
Description
1
Router LSA
Produced by every router and includes all the router's links,
interfaces, state of links, and cost; flooded within a single
area
2
Network LSA
Produced by every DR on every broadcast or nonbroadcast
multiaccess (NBMA) network; lists all the routers in the
multiaccess network; contained within an area
3
Summary LSA for ABRs
Produced by area border routers (ABRs); sent into an area to
advertise destinations outside the area
4
Summary LSA for ASBRs
Originated by area border routers (ABRs); sent into an area
by the ABR to advertise the AS boundary routers (ASBRs)
5
AS External LSA
Originated by ASBRs; advertises destinations external to
the OSPF AS; flooded throughout the entire OSPF AS
7
Not-so-stubby area
External LSA
Originated by ASBRs in a not-so-stubby area (NSSA); not
flooded throughout the OSPF AS, only to the NSSA
OSPF Router Types
Table 8-4
OSPF Router Type
Description
Internal router
Interfaces belong to the same OSPF area
Area Border Router (ABR)
Connects to more than one area; generates summary LSAs
ASBR
Injects external routes into the OSPF protocol
Backbone router
At least one interface connects to area 0
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