ICND2 Section 3 - IPv4 Routing Protocols

Question 1

In OSPF, what’s the difference between the init and 2way states?

Answer 1

Init specifies that the router has received a hello packet from its neighbor, but the receiving router’s ID was not included in the hello packet.
2way is attained when the router receiving the hello packet sees its own Router ID within the received hello packet’s neighbor field.

Question 2

What are the 8 states of OSPF neighbors?

Answer 2

Down
Attempt
Init
2way
ExStart
Exchange
Loading
Full

Question 3

In what type of environment is an OSPF state of Attempt valid?

Answer 3

NBMA only

Question 4

What kind of packet is used during the ExStart and Exchange phases?

Answer 4

DDP

Question 5

What does DDP stand for?

Answer 5

Database Descriptor Packet

Question 6

What kind of packets are used during the Loading phase?

Answer 6

LSU

Question 7

What does an LSU contain?

Answer 7

One or several LSA’s

Question 8

What information is in a Network LSA?

Answer 8

the DR on a broadcast segment lists which routers are joined together by the segment. The LSID of the type 2 LSA is the IP interface address of the DR.

Question 9

What information is in a Summary LSA?

Answer 9

Information about subnets in other areas
Subnet ID,
mask,
RID of ABR that advertises the LSA

Question 10

In what OSPF phase do neighbors pass each other their LSA’s?

Answer 10

Loading

Question 11

What are the 2 primary timers in OSPF?

Answer 11

Hello

Dead Interval

Question 12

What are the default settings for the OSPF hello and dead intervals on non-serial interfaces?

Answer 12

Hello = 10 seconds

Dead Interval = 4*(HelloInterval)

Question 13

For DROthers, what is the maximum state that they reach with each other?

Answer 13

2way

Question 14

List the first 3 OSPF LSAs

Answer 14

Router
Network
Summary

Question 15

What info is in a Router LSA?

Answer 15

RID
Directly connected interface info
-network
-mask
-cost

Question 16

What is the area scope of type 1 and 2 LSAs?

Answer 16

Intra-area only

Question 17

What router type advertises type 3 LSAs, and what are they used for?

Answer 17

ABRs advertise them.

They are used for advertising networks from one area into another.

Question 18

When an ABR floods a summary LSA, what is the advertising router set to?

Answer 18

Itself, so the ABR looks like the one that has all of the routes directly connected.

Question 19

OSPF command to set the number of paths that will be used in ECMP

Answer 19

maximum-paths

Question 20

How does route poisoning work?

Answer 20

A route that is no longer valid will be advertised with the max metric, to let all other routers know that it’s no longer available.

Question 21

How does split horizon work?

Answer 21

Do not advertise routes out an interface which is the exit interface to get to said routes.

Question 22

When does EIGRP send full and partial updates?

Answer 22

Full on neighbor adjacency

Partial as needed when network topology changes

Question 23

What are the 2 primary timers for EIGRP?

Answer 23

Hello

Hold

Question 24

What are the default values for the Hello and Hold timers in EIGRP?

Answer 24

Hello = 5 seconds
Hold = 3xHello, or 15 seconds by default

Question 25

What are EIGRP’s 2 primary metrics?

Answer 25

Bandwidth and Delay

Question 26

What is the multicast address for EIGRP?

Answer 26

224.0.0.10

Question 27

Does EIGRP ever flood updates periodically?

Answer 27

No, only during adjacency setup or topology changes

Question 28

What are the 3 required and 1 optional attributes that must pass before an EIGRP adjacency will be established?

Answer 28

Required:
1. Same AS number
2. Same IP subnet
3.  Matching K values
Optional:
1. Authentication, if configured, must match.

Question 29

What is the Feasible Distance in EIGRP?

Answer 29

The metric of an EIGRP route on the local router.

Question 30

What is the Reported Distance in EIGRP?

Answer 30

The next-hop router’s best metric for a FD subnet

Question 31

What algorithm is used by EIGRP

Answer 31

DUAL

Question 32

What does DUAL stand for?

Answer 32

Diffusing Update ALgorithm

Question 33

Does the EIGRP ASN need to match between neighbors?

Answer 33

Yes

Question 34

Syntax to include interfaces into EIGRP

Answer 34

conf t
router eigrp
network \

Question 35

What 5 attributes must match for OSPF neighbors to become adjacent?

Answer 35

1. Same subnet
2. Hold/dead timers
3. Authentication
4. Same area
5. Same interface MTU

Question 36

What 3 attributes must match for EIGRP neighbors to become adjacent?

Answer 36

1. Same subnet
2. Same ASN
3. Matching K-values