OSPF Flashcards
(34 cards)
What does OSPF stand for?
Open Shortest Path First
Is OSPF a standard or proprietary protocol?
OSPF is an open standard protocol.
What type of routing protocol is OSPF?
OSPF is an Interior Gateway Protocol (IGP).
What kind of protocol is OSPF in terms of operation?
OSPF is a link-state protocol.
What is the goal of a routing protocol like OSPF?
To learn routes and determine the best path to each network.
How does OSPF routers learn about the network topology?
By exchanging Link-State Advertisements (LSAs).
What is an LSA?
Link-State Advertisement - a packet that contains information about a router, its interfaces, and their state.
What is the Link-State Database (LSDB)?
A database that stores all LSAs collected from OSPF routers in the same area.
What is the ultimate goal of OSPF routers regarding LSDBs?
Each router has an identical LSDB to ensure a consistent network view.
What are the three main steps in OSPF operation?
- Form neighbor relationships
- Exchange LSDB information
- Calculate best routes and update routing table.
What is a Router ID (RID) in OSPF?
A unique identifier in the format of an IPv4 address used to identify an OSPF router.
How is a Router ID selected if not manually set?
Highest loopback IP address, or highest active non-loopback IP address if no loopback exists.
What are the requirements for OSPF routers to form a neighbor relationship?
Same area ID, same subnet, matching hello/dead timers, matching authentication, matching stub flag, unique Router IDs.
What is the default hello interval on broadcast and point-to-point networks?
10 seconds.
What happens if the dead timer expires without receiving a hello?
The router assumes the neighbor is dead and removes it from the neighbor table.
What is the two-way state in OSPF?
The state where routers recognize each other as neighbors but do not yet exchange full LSDBs.
What is a Designated Router (DR) in OSPF?
A router elected to manage LSDB updates on a broadcast network.
What is a Backup Designated Router (BDR) in OSPF?
A router elected to take over if the DR fails.
How is the DR/BDR election decided?
By highest OSPF priority (default 1), then by highest Router ID.
Do DR/BDR elections occur on point-to-point links?
No, only on broadcast and multi-access networks.
Which routers form full neighbor relationships on broadcast networks?
Only routers and the DR/BDR form full neighbor relationships; other routers remain in two-way state.
What is the ‘ExStart’ state in OSPF?
The state where routers determine master/slave roles and prepare to exchange database information.
What is a Database Description (DBD) packet in OSPF?
A summary of LSAs a router knows about, used during database exchange.
What is a Link-State Request (LSR) in OSPF?
A request sent by a router for specific LSAs it is missing.
