OSPF Flashcards
Once adjacencies have been formed, OSPF will then start sending these out
DBD Packets (Database Description Packets)
A router will send out and listen for these when OSPF is enabled on an interface
OSPF Hello Packets
If a router is missing information about any of the networks it received in the DBD, it will send the neighbor one of these
LSR (Link State Request)
This is the step when adjacent routers will tell each other the networks they know about with this type of packet
DBD (Database Description Packets)
These packets contain routing updates
LSA (Link State Advertisement)
These packets contain a list of Link State Advertisements (LSAs) which should be updated and that will be used during flooding
LSU (Link State Update)
This is a routers response to a Link State Request (LSR) asking for more information
Link State Advertisement (LSA)
Scenario: If a new link was added to the network or if a link went down and new information needs to get flooded everywhere so all routers can know about it this type of packet would be processed
LSU (Link State Update)
Receiving routers acknowledge Link State Advertisements (LSA) through these types of packets
LSAck (Link State Acknowledgement)
OSPF sends Hello Packets using Broadcast
False. Hello Packets use Multicast
What are the 6 Steps / Characteristics of OSPF?
- Discover Neighbors
- Form Adjacencies
- Flood the Link State Database
- Compute the Shortest Path
- Install the Best Routes Into The Routing Table
- Respond to Network Changes
What will happen if a router running OSPF has 2 interfaces with different Process IDs?
It will not share information about it’s routes with either side of the link due to separate Link State Databases
Does the network command in OSPF default to the classful boundary?
No. That’s one of the differences between OSPF and EIGRP
Do you have to enter a wildcard mask in OSPF?
Yes
What is a simple OSPF configuration?
router ospf 1
network 10.0.0.0 0.0.255.255 area 0
If a network contained routers with interfaces such as:
10.1.0.1/24
10.0.1.1/24
10.0.2.1/24
And you configured a network command for OSPF as:
network 10.0.0.0 0.0.255.255 area 0
What networks would get advertised in the routing table?
10.0.1.0/24
10.0.2.0/24
10.1.0.0 would not be advertised because it doesn’t match the 10.0.X.X space that the network command is looking for.
Use this command to see if neighbor routers have peered and formed an adjacency
show ip ospf neighbor
What are the commands to enter a Router ID for OSPF?
router ospf 1
router-id {router id}
If you need to restart OSPF what command can you use?
clear ip ospf process
What are the commands for a passive loopback interface in OSPF?
router ospf 1
passive-interface loopback0
How would you set all interfaces to passive on a router using OSPF?
router ospf 1
passive-interface default
What are the commands to enter a default route injection into OSPF?
ip route 0.0.0.0 0.0.0.0 {next-hop-address}
router ospf 1
default-information originate
This is the top level or Area 0 when it comes to OSPF routers
The Transit Area or Backbone
For a router to form a full adjacency with a neighbor, it must be configured in the same what?
Area