1200 ENSA - OSPF (module 1 & 2)

What did Routing Information Protocol (RIP) rely on as the only metric for determining best route?

Hop count

What are the 5 different routing protocol messages/packets that OSPF has?

• Hello packet

• Database description packet

• Link-state request packet

• Link-state update packet

• Link-state acknowledgment packet

What does LSDB stand for?

what does it do?

Link-state database

create the topology table

what does the adjacency database create?

the neighbor table

What does the forwarding database create?

the routing table

the router builds the topology table using the results of which algorithm?

How is the spf tree created?

Dijikstra Shortest-path first (SPF)

places each router at the root of the tree and calculating the shortest path to each node

which two databases are unique to the router?

adjacency and forwarding databases

what is the simplified process of link-state routing?

establish neighbor adjacencies and tell them how much their paths cost

build the link state database

execute the SPF algorithm and choose the best routes

when ospf is multiarea, which processes are kept within the area?

recalculating the database, all SPF algorithm functions

the hierarchical-topology design in mutliarea ospf offers which advantages?

smaller routing tables

reduced link-state update overhead

reduce frequency of spf calculations

Which OSPFv3 feature supports both ipv4 and ipv6?

Address Families

What is a type 2 DBD packet?

is an abbreviated list of the LSDB of the sending router, and is used by the receiving router to check against the local LSDB

What is a type 3 LSR packet?

is a packet used by the receiving routers to request more information about an entry in the DVD

What is a type 4 LSU packet?

is a packet used to reply to an LSR packet

What is a type 5 LSAck packet?

a packet used to acknowledge the receipt of a type 4 LSU

are DR and BDR elections pre-emptive?

No

Which ipv4 multicast address is reserved for all routers

224.0.0.5

make sure to study Establishing

Neighbor Adjacencies!!!

what are the three steps of the process of exchanging and synching LSBDs

make sure to look through this 1.3

Deciding the first router

Exchanging DBDs

Sending an LSR

in the exchange state, which router will send their database descriptor packets first?

the router with the highest router ID

In a multiaccess LAN environment, the router with the highest router ID is elected the what?

DR

if the router ID is not explicitly configured, the router chooses the highest IPv4 address of which interfaces?

The loobacks

true or false, a router interface needs OSPF enabled for that interface to be chosen as the router ID?

False

What are passive interfaces?

interfaces that prevent transmission of routing messages through the interface, but still allow that network to be advertised to other routers

what three ways can sending out unneeded OSPF messages out of a lan can impact a network?

inefficient use of bandwidth

inefficient use of resources

increased security risk

in what way are multiaccess networks unique?

one router controls the distribution of LSAs

What is the DR responsible for?

responsible for collecting and distributing LSAs sent and received

What multicast address does the DR use?

224.0.0.5

DROTHERs use which multicast address?

which routers listen for this address?

224.0.0.6

only the DR and BDR listen for this multicast address

please go over the Verify DR/BDR adjacencies!!

section 2.3

the cisco cost of an interface is inversely proportional to the bandwidth of what?

the interface; the higher the bandwidth, the lower the cost and vice versa

the router located between an OSPF routing domain and a non-OSPF network is called what?

Autonomous system boundary router

in the init state, what happens?

what does it transition to?

hello packets are received from the router, they contain the router ID of the sending router

transitions to two way state

in the two way state, what happens?

what does it transition to?

communication between routers is bidirectional, and the DR and BDR are elected

transitions to the exstart state

in the exstart state, what happens?

what does it transition to?

on point-to-point networks, the two routers decide which router will initiate the DBD packet exchange and decide upon the initial DBD packet sequence number

transitions to exchange state

in the exchange state, what happens?

what does it transition to?

Routers exchange DBD packets.

if additional router information is required then transition to loading,otherwise, transition to full

in the loading state, what happens?

what does it transition to?

LSRs and LSUs are used to gain additional route info, and routes are processed using the SPF algorithm

transitions to the full state

What three states are part of establishing a neighbor adjacency?

down, init, and two way

If two adjacent neighbors are interconnected over a point-to-point link, then they immediately transition from which state to what state?

two-way to exstart