• Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off
Reading...
Front

Card Range To Study

through

image

Play button

image

Play button

image

Progress

1/37

Click to flip

Use LEFT and RIGHT arrow keys to navigate between flashcards;

Use UP and DOWN arrow keys to flip the card;

H to show hint;

A reads text to speech;

37 Cards in this Set

  • Front
  • Back

What kind of protocol is OSPF?

IGP



Interior Gateway Protocol

OSPF

Open Shortest Path First

Is OSPF Link State or Distance Vector?

Link State

Link State Protocol
These are like your navigation system, they have a complete map of the network.

If you have a full map of your network you can calculate the shortest path to all different destinations out there.

How are Link-state routing protocols operated?

By sending LSA (Link-state advertisements)

Why do routers need LSA?
Link State Advertisement

So they can build LSDB (Link-State database)
A full LSDB is called ________________?

Topology

NOTE:
You could compare this to a full map of your country.

SPF

Shortest Path First



The algorithm used to calculate the shortest route

area 0 is normally referred to as ______________?

Backbone area

To connect various areas whom must they travel through?

Area 0 aka backbone

If you are using another routing protocol what must you use?

Redistribution

What are routers in the backbone area called?

Backbone Routers

What are the routers between areas called?

Area Border Routers



ABR

Routers that run OSPF and are connected to another network that runs another routing protocol are called

Autonomous System Border Routers



ASBR

In OSPF if you receive packets from a router, you become _______________?

Neighbors

Router ID in OSPF

This is the highest IP address on any active interface or loopback address

Hello/Dead Interval:
Every __ Seconds we are going to send hello packet, if we don't hear any hello packets from out neighbor for ___ seconds we declare you "dead" and we are no longer neighbor.

NOTE:
These values must match on each side

Neighbors

All other routers who are your neighbors specified in the hello packet

Area ID
This is the area you are in. This value has to match on both sides in order to become neighbors.

Router Priority

This value is used to determine who will become designated or backup designated router.

DR and BDR IP address

Designated and Backup designated router

Authentication password
You can use clear text and MD5 authentication for OSPF which means every packet will be authenticated.

NOTE:
You need the same passwords on both routers for them to work

Stub Area Flag

All routers in a stub area must have the stub area flag set. This means that all routers in the area must be configure with this command if the ABR has the area configured as a stub.

Benefits of an unadvertised loopback address

1. Used as OSPF Router ID


2. Saves Address Space


3. Unable to use to connect to router

Benefits of Advertised Loopback address

1. Used as OSPF router ID


2. Uses address Space


3. Able to use to connect to router

Why do you use a loopback address instead of the highest address?

The loopback address will never go down.

What is the OSPF metric called?

Cost

Requirments of Load Balancing
1. Paths must have equal costs
2. equal cost paths will be placed in routing table
3. Maximum of 16 paths
4. to make paths equal cost, change the "cost" of a link

Aging Timer

Each LSA has an aging timer which carries the link-state age field. By default each OSPF LSA is only valid for 30 minutes.


Sequence Number

A number assigned by OSPF, this allows routers to know if the information they received is the same age or newer than the information they have.

LSU

Link Status Update



In OSPF the router uses the sequence number to determine if it needs to update the link status

What are the four categories the LSA will check to verify if a update is required?
1. Higher sequence number
2. Higher checksum
3. An age equal to the maximum age
4. If the link-state age is much younger
What do sequence numbers look like for OSPF LSAs?
1. There are 4 bytes is 32-bits
2. Begins with 0x80000001 and ends at 0x7ffffff
3.Every 30 minutes each LSA will age out and will be flooded (the sequence number will increment by 1)

What command shows us the LSDB?

Link State Database



show ip ospf database

router LSA

This is the link ID

What is the first sequence number
0x80000001 and ends at 0x7FFFFFF

NOTE: This number starts over after it reaches 0x7FFFFFF

If you want to reset the LSA on a router what command will you use?

clear ip ospf process