Ospf advance

What is Area 0 in OSPF?

backbone area, the central and most important area in OSPF.

Why must all other OSPF areas connect to Area 0?

it handles the routing information and ensures routes are shared correctly across the network.

How does Area 0 help prevent routing loops in OSPF?

serves as a central point where routing information is injected and managed, maintaining efficient routing.

What are Area Border Routers (ABRs) in OSPF?

OSPF routers connected to both Area 0 and another OSPF area.

What is the role of an ABR in OSPF?

responsible for advertising routes from one area and injecting them into a different OSPF area.

Why must every ABR participate in Area 0?

to ensure that routes can be advertised into other OSPF areas.

How do ABRs manage routing information?

ABRs compute an SPF tree for each area they participate in to manage and calculate routing information.

What is the format of an OSPF Area ID?

32-bit field and can be formatted in simple decimal or dotted-decimal format.

How does OSPF advertise the Area ID in hello packets?

OSPF advertises the Area ID in dotted-decimal format in the hello packet.

What happens when OSPF neighbors become adjacent?

Link-State Databases (LSDBs) synchronize between the OSPF routers.

What does an OSPF router do when it adds or removes a network link?

router floods a Link-State Advertisement (LSA) out all active OSPF interfaces.

What information does an LSA contain?

complete list of networks advertised from the router.

What is Type 1 or router LSA in OSPF?

advertises the LSAs that originate within an area.

What does Type 2 or network LSA advertise?

advertises a multi-access network segment attached to a DR.

What is the purpose of Type 3 or summary LSA?

advertises network prefixes that originated from a different area.

What does Type 4 or ASBR summary LSA advertise?

advertises a summary LSA for a specific ASBR.

What information is included in Type 5 or AS external LSA?

advertises routes that have been redistributed.

What does Type 7 or NSSA external LSA advertise?

advertises redistributed routes in NSSAs.

What initial fields are included in a Type 1 LSA?

include the RID of the advertising router, age, sequence, link count, and link ID.

What information is listed under the number of links in a Type 1 LSA?

Each OSPF-enabled interface on the router is listed, including the link type, neighbor router identification, and interface metric.

How is the neighbor router identified in a Type 1 LSA?

on multi-access network segments with designated routers (DRs), the DR's interface address is used for identification.

What does a Type 2 LSA represent?

multi-access network segment that uses a Designated Router (DR).

Who advertises the Type 2 LSA?

The DR

What information does a Type 2 LSA provide?

all the routers attached to the network segment.

What is the role of ABRs concerning Type 3 LSAs?

ABRs create and advertise to ensure that networks associated with Type 1 LSAs are reachable in non-originating OSPF areas.

What happens when Type 1 LSAs are received from an area?

LSAs received from an area create Type 3 LSAs in the backbone area and non-backbone areas.

How does an ABR handle Type 3 LSAs received from Area 0?

ABR creates Type 3 LSAs for the non-backbone area based on the Type 3 LSAs received from Area 0.

How are Type 3 LSAs from non-backbone areas handled?

only inserted into the LSDB for the source area; ABRs do not create Type 3 LSAs for other areas, including segmented Area 0.