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37 Cards in this Set
- Front
- Back
What kind of protocol is OSPF? |
IGP
Interior Gateway Protocol |
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OSPF |
Open Shortest Path First |
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Is OSPF Link State or Distance Vector? |
Link State |
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Link State Protocol
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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. |
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How are Link-state routing protocols operated? |
By sending LSA (Link-state advertisements) |
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Why do routers need LSA?
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Link State Advertisement
So they can build LSDB (Link-State database) |
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A full LSDB is called ________________?
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Topology NOTE: You could compare this to a full map of your country. |
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SPF |
Shortest Path First
The algorithm used to calculate the shortest route |
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area 0 is normally referred to as ______________? |
Backbone area |
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To connect various areas whom must they travel through? |
Area 0 aka backbone |
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If you are using another routing protocol what must you use? |
Redistribution |
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What are routers in the backbone area called? |
Backbone Routers |
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What are the routers between areas called? |
Area Border Routers
ABR |
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Routers that run OSPF and are connected to another network that runs another routing protocol are called |
Autonomous System Border Routers
ASBR |
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In OSPF if you receive packets from a router, you become _______________? |
Neighbors |
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Router ID in OSPF |
This is the highest IP address on any active interface or loopback address |
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Hello/Dead Interval:
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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 |
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Neighbors |
All other routers who are your neighbors specified in the hello packet |
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Area ID
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This is the area you are in. This value has to match on both sides in order to become neighbors.
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Router Priority |
This value is used to determine who will become designated or backup designated router. |
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DR and BDR IP address |
Designated and Backup designated router |
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Authentication password
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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 |
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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. |
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Benefits of an unadvertised loopback address |
1. Used as OSPF Router ID 2. Saves Address Space 3. Unable to use to connect to router |
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Benefits of Advertised Loopback address |
1. Used as OSPF router ID 2. Uses address Space 3. Able to use to connect to router |
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Why do you use a loopback address instead of the highest address? |
The loopback address will never go down. |
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What is the OSPF metric called? |
Cost |
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Requirments of Load Balancing
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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 |
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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.
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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. |
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LSU |
Link Status Update
In OSPF the router uses the sequence number to determine if it needs to update the link status |
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What are the four categories the LSA will check to verify if a update is required?
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1. Higher sequence number
2. Higher checksum 3. An age equal to the maximum age 4. If the link-state age is much younger |
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What do sequence numbers look like for OSPF LSAs?
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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) |
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What command shows us the LSDB? |
Link State Database
show ip ospf database |
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router LSA |
This is the link ID |
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What is the first sequence number
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0x80000001 and ends at 0x7FFFFFF
NOTE: This number starts over after it reaches 0x7FFFFFF |
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If you want to reset the LSA on a router what command will you use? |
clear ip ospf process |