OSPF Flashcards
What algorithm does OSPF use to choose best path ?
Dijkstra’s algorithm
What is the metrics used in determining what route gets installed in the routing table ?
Administrative Distance
What is the Administrative Distance of OSPF ?
110
OSPF Packet types
hello, database description, request, update, acknowledgement
What hello packets are used for ?
Establish neighbor adjacencies
Single - Area OSPF
Routers are contained in one area
backbone area
known as area 0
in smaller networks with few routers
Multiarea OSPF
Use hierarchical scheme
Areas connected to area 0
Used in large networks
Why have a DR/DBR election ?
Reduce the no of adjacencies over a multi-access network like Ethernet
Reduce no. of LSAs sent
Used to identify an OSPF router
Router IDs
What if no router ID is configured ?
Highest configure loopback interface is used
No configured loopback interfaces to identify router id
Highest active IPv4 address is used
Command to verify the router ID
show ip protocols
A command that does not send OSPF messages.
Passive interface
cost of 10 Gbps Ethernet
1
100 Mbps Ethernet
1
1 Gbps Ethernet
1
Concept of OSPF Metric = Cost
lower bandwidth interface has a higher cost
Adjusting reference bandwidth
auto cost reference-bandwidth 10000
Multiarea OSPF
Reduces processing and memory overhead
What is used to create the OSPF neighbor table?
adjacency database
A router that has interfaces attached to multiple areas
Area Border Router (ABR)
A router in the backbone area, Set to 0
Backbone Router
A router that has all of its interfaces in the same area
Internal router
A router that has at lease one interface attached to an external internetwork
Autonomous System Boundary Router (ASBR)
