1So every router has a full view of the network and can calculate the best path itself
OSPF link-state approach
2it is faster than RIP because it reacts to topology changes instead of relying on periodic updates
OSPF
3To reduce CPU load, memory use, and LSA flooding
OSPF need areas
4It is the backbone that connects all other areas
Area 0
5Why does OSPF use cost instead of hop count?
Because cost reflects bandwidth, not just number of routers
6Why does a lower cost mean a better path in OSPF?
OSPF selects paths with the least cumulative cost
7Why does OSPF run SPF only when needed?
To reduce CPU usage
8Why are Hello packets sent?
To discover neighbors and maintain adjacencies
9Mismatched timers or area IDs prevent adjacency, thats why
Hello parameters must match
10Why does a router get stuck in INIT state?
It receives Hellos but its router ID is not acknowledged
11Why is the TWO-WAY state important?
It confirms bidirectional communication
12Why doesn’t full adjacency always form?
Because on multiaccess networks only DR/BDR form full adjacencies
13Why does OSPF go through ExStart and Exchange?
To synchronize databases
14Why is FULL state important?
It means databases are synchronized
15To control LSA flooding on multiaccess networks, the _____________________
OSPF elects a DR
16BDR Importance
To immediately replace the DR if it fails
17DR election should not be preemptive
Prevent instability from constant role changes
18Why can priority 0 never be DR or BDR?
It explicitly removes the router from election
19Why does highest router ID matter?
It breaks ties when priorities are equal
20Why is DR/BDR unnecessary on point-to-point?
Only two routers exist, so flooding is manageable
21Why does OSPF maintain multiple databases?
Each database serves a different routing purpose
22Why is the LSDB the same on all routers in an area?
So SPF calculations are consistent
23Why are LSAs flooded instead of routed?
To ensure all routers learn topology changes
24Why does excessive LSA flooding cause problems?
It increases CPU and bandwidth usage
25Why does multiarea OSPF limit LSA scope?
To keep recalculations within an area
26Why do FastEthernet and Gigabit have the same cost by default?
Because the reference bandwidth is too low
27Why change reference bandwidth?
To differentiate high-speed links
28Why does Dead interval removal trigger flooding?
So all routers know the neighbor is down
29To maintain neighbor adjacency
Hello and Dead timers should match
30Why is accumulated cost used?
To measure total path quality
31Why does a router check ACLs sequentially?
It stops at the first matching ACE
32there should be implicit deny at the end
To block any traffic not explicitly permitted
33Why are ACLs not bidirectional by default?
Traffic direction must be explicitly defined
34Why do inbound ACLs improve efficiency?
They drop unwanted traffic early
35To stop unwanted traffic quickly, Extended ACLs should be
Near the source
36Why should standard ACLs be near the destination?
They lack destination awareness
37Why does wildcard mask 0 mean match?
Because the bit must be checked
38Why does wildcard mask 1 mean ignore?
Because the bit does not matter
39Why use host keyword?
It matches a single IP exactly
40Why use any keyword?
It matches all IP addresses
41Why use named ACLs?
They are easier to read and edit
42To insert or remove ACEs without recreating ACLs we use
sequence numbers
43Wrong direction causes unexpected traffic drops thats why we
verify ACL placement
44To allow return traffic for TCP connections we use
established keyword