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43 Cards in this Set
- Front
- Back
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Scalability
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Accommodate growth easily
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What does scalability require?
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Hierarchical addressomg
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How often do fast convergence changes happen?
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17-30 seconds on most networks
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OSPF
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Open Shortest Path First
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How does OSPF work?
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- Picks the widest fastest path
- Relies on accumulated bandwidth |
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What is the Dijkstra Algorithm?
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- Monitors link states
- Places a value on Bandwidth - lowest cost wins |
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What is the OSPF metric called?
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cost
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Is OSPF open source or closed source?
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Open source
NOTE: Local network programming can be used to modify and streamline |
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What are some disadvantages of OSPF?
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- more difficult to understand
- can result in link flooding on slow flapping links (up and down network) - Bigger topology and routing table databases = more DRAM |
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Why is it a disadvantage to have a slow flapping link in OSPF?
NOTE: Flapping is a network that is up and down. |
- algorithm constantly updating route tables
- difficult to achieve true convergence until the link stabilize - Higher CPU utilization |
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OSPF:
What is area? |
- An administrative domain of OSPF routers
- Area 0 is the backbone area. OSPF cannot run without area 0 |
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What is the backbone area of OSPF?
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area 0
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OSPF:
What is a Adjacency (neighbor) |
Two routers on the same OSPF area on the same physical link/subnet
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OSPF:
What is a router ID? |
Highest configured IP address of an active interface (or loopback address if configured)
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OSPF:
What is the master or designated router? |
- used to update all OSPF routers in a single broadcast network
- same role as Master in Point to Point networks |
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OSPF:
What is Cost? |
sum of the cost of the link accumulated cost of bandwidth
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What is the command to get into OSPF mode on the router?
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router ospf 1
NOTE: The number 1 is simply a process id |
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When you use the "router ospf 1" command what is happening in the router?
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Router ospf commands calls up the OSPF sub routines from IPS and moves them into DRAM
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OSPF:
What does the process id do? |
Helps the Dijkstra algorithm track the mathematics and keep them all together
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What are some addition parameters often used when configuring OSPF?
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- Router ID
- Router Priority - Bandwidth parameters (link cost, etc) |
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How are interfaces configured in OSPF?
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Interfaces can be configured individually, or they can be configured as a group using a wildcard mask,
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What commands would you enter to OSPF for an area
10.0.1.5 0.0.0.0? |
- router ospf 1
- network 10.0.1.5 0.0.0.0 area 0 |
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OSPF Adjacency States:
What is Down? |
no communication received
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OSPF Adjacency States:
What is attempt? |
only for NBMA environments
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OSPF Adjacency States:
What is Init State? |
Hellos exchanged
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OSPF Adjacency States:
What is two way? |
Established communication
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OSPF Adjacency States:
What is Exstart? |
Elect a Master/Slave
1. Exchange link state database 2. Discover Routes to all networks |
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OSPF Adjacency States:
What is exchange? |
This is when Databases are swapped
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OSPF Adjacency States:
What is loading? |
1. Build Routing Table
2. Send receive updates |
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OSPF Adjacency States:
What is full State? |
Adjacency Complete
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Common commands in troubleshooting OSPF
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- show ip route
- show ip protocols - show run |
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Common commands specific to OSPF often used in troubleshooting.
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- show ip OSPF neighbor
- show ip OSPF database |
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Types of OSPF networks?
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- Point to Point
- Broadcast Multicast - Point to Multipoint - Non Broadcast Multi Access |
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What happens with a Broadcast MultiAccess?
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There is an election to determine the designated router(DR) and the backup designated router (BDR)
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Point to Point networks
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Have a master and a slave.
NOTE: The master is the intitiator |
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What is a non Broadcast Multi Access network?
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Designated Router must me specified
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What is Point to Multipoint networks?
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- This has a Master and slaves
- Single provider link is provisioned with subinterface |
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What happens with the subinterfaces on a point to multipoint network?
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They lead to a different WAN endpoint/network
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What can a technician do with the bandwidth on a subinterface for a point to multipoint connection?
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Each subinterface can have a different bandwidth assigned out of the total bandwidth assigned out of the total bandwidth the provider is paid for
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What is the network command used for in OSPF?
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includes interfaces into an area
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What state is an OSPF router in once the adjacency is completed?
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Full
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What area must exist for an OSPF network to function?
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0
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What does a 0 do in a wildcard mask>
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Forces mathematical matches on corresponding bits in the IP address
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