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35 Cards in this Set

  • Front
  • Back

If you see OSPF in wireshark what would the ip packet look like?

protocol ID 89

What command allows you to look at the ospf packet in your router?

debug ip ospf packet

V:2
stands for OSPF version 2. If you are running IPv6 you will use version 3.

T:1

stands for OSPF packet number 1 which is a hello packet

L:48

is the packet length in bytes



NOTE:


This packet is 48 bytes

RID 1.1.1.1

This is the router ID

CHK 4D40

is the checksum of this OSPF packet so we can check if the packet is corrupt or not

AUT:0

is the authentication type



0 = No authentication

AUT:1

is the authentication type



1 = clear text


AUT:2

is the authentication type



2 = MD5

AUK

if you enable this authentication you'll see some information here

Hello

Neighbor discovery, Build neighbor adjacencies and maintain them

DBD

This packet is used to check if the LSDB between 2 routers is the same. The DBD is summary if the LSDB

LSR

requests specific link-state records from an OSPF neighbor

LSU

Sends specific link-state records that were requested. This packet is like an envelope with multiple LSA in it

LSAck

OSPF is a reliable protocol so we have packet to acknowledge the others

AID

Is the area ID in dotted decimal.



NOTE:


You can write the area in decimal (area 0) or dotted decimal

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 LSU (link state update packet)

Full

OSPF routers now have adjacency

What are the 7 states OSPF must go through before they become neighbors?

1. Down


2. Init


3. Two-way


4. Exstart


5. Exhange


6. Loading


7. Full

What are the types of OSPF Packets
1. Hello
2. Database Description (DBD)
3. Link-State Request (LSR)
4. Link-State Update (LSU)
5. Link-State Acknowledgment (LSAck)

When an OSPF Router puts an entry in the OSPF neighbor table what OSPF state is it in?

Init State

When an OSPF Router has to respond to an OSPF Router with a hello packet, what OSPF state is it in?

Two-way



NOTE


This is unicast and the neighbor field will include all neighbors

If the routers are going into two-way state and you are using a multi-access network. What does an OSPF have to elect?

A Designated Router (DR) or Backup Designated Router (DR)

In exstart how is a master determined?

The one with the highest router ID

What state are routers sending a database description (DBD) with a summary of the Link-State Database (LSDB)?

Exchange State

When are routers in a loading state?

When the routers start sending a Link-State Request (LSR)



NOTE


The other router will send a Link state Update (LSU)

What is the packet used to let the neighbor router know they are in the full state?

LSack

When both OSPF routers have synchronized what state are they in?

Full

If you want to see the OSPF adjacency in progress what command can you use?

debug ip ospf adj