OSPF

Question 1

Router ID (RID) selection order of precedence?

Answer 1

1. Manually configured under the global OSPF configuration section
2. Highest numeric IPv4 address on a loopback interface
3. Highest numeric IPv4 address on any non-loopback interface
   * Can even be in the DOWN/DOWN state, but cannot be shut down!
   * Multiple OSPF process on same node need unique RID values
   * This includes VRFs!

Question 2

OSPF Packet Types

Answer 2

Hello
Database Descriptor
Link State Request
Link State Update
Link State Acknowledgment

Question 3

Which multicast address is used for OSPF?

Answer 3

224.0.0.5

Question 4

What is a type 1 LSA?

Answer 4

Router LSA. Always within same area.

Question 5

What is type 2 LSA?

Answer 5

Network LSA

Question 6

What is type 3 LSA?

Answer 6

Summary LSA sent from one area to another. Allows routers in other areas to learn about prefixes from other areas.

Question 7

What is type 4 LSA?

Answer 7

summary ASBR LSA - Has info about where to find a ASBR.

Question 8

What is type 5 LSA

Answer 8

External LSA. Has information about a prefix sent from another AS. Route that has been redistributed into OSFP. (O E1 or O E2).

Question 9

What is type 6 LSA

Answer 9

multicast

Question 10

What is type 7 LSA

Answer 10

Basically a type 5 for NSSA. Will get turned into type 5 once the LSA leaves the NSSA.

Question 11

Real Niggas Slap Ass Eat Noodles

Answer 11

Router
Network
Summary
ASBR Summary
External
NSSA

Question 12

OSPF has to get through 7 states in order to become neighbors. What are they?

Answer 12

Down: no OSPF neighbors detected at this moment.
Init: Hello packet received.
Two-way: own router ID found in received hello packet.
Exstart: master and slave roles determined.
Exchange: database description packets (DBD) are sent.
Loading: exchange of LSRs (Link state request) and LSUs (Link state update) packets.
Full: OSPF routers now have an adjacency.