CCNA routing protocol
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Transcript of CCNA routing protocol
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2007 Cisco Systems, Inc. All rights reserved. Cisco Public
ITE PC v4.0
Chapter 1 1
Link-State Routing
Protocols
Routing Protocols andConcepts Chapter 10
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Chapter 1 2 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Objectives Describe the basic features & concepts of link-state
routing protocols.
List the benefits and requirements of link-state routingprotocols.
Key Terms
Link-state Routing Protocol
Shortest Path First
Link-state Packet
Link-state Database
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Chapter 1 3 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Whos Responsible for Link-State Protocols?
Dijkstra's algorithm, solves the single-source shortestpath problem for a directed graph with nonnegativeedge weights.
Wikipidia
Edsger Dijkstra
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Chapter 1 4 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Link-State Routing Protocols
Also known as shortest path first algorithms
These protocols built around Dijkstras SPF
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Chapter 1 5 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Difference Between LS and DV Protocols
Distance Vector protocols understand distant networksbased on direction (example: signs)
Link State protocols create a topology (example: map)
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Chapter 1 6 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Step 1: Determine Connected Networks
Router identifies directlyconnected networks
Includes:
Link - Router Interface
State - Information aboutthe condition of the links
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Chapter 1 7 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Step 2: Establish Neighbor Adjacencies
Hello packets are exchangedbetween routers with connectedinterfaces
Once routers learn it has neighbors
they form an adjacency
- Two adjacent neighbors willexchange hello packets
-These packets will also serve as
keep alives Verify that neighbor and stateshave not changed
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Chapter 1 8 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Step 3: Builds the Link-State Packet
Each router builds its ownLink State Packet (LSP)
Contents of LSP:
- State of each directlyconnected link
- Includes informationabout neighbors such as
neighbor ID, link type, &bandwidth.
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Chapter 1 9 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Step 4: Flooding LSPs to Neighbors
Once LSP are created they are forwarded out toneighbors
Neighbors store the LSPs in a database
After receiving the LSPs, the neighbor continues toforward it throughout routing area
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Chapter 1 10 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Flooding LSPs to Neighbors (2)
LSPs are sent out under the following conditions
-Initial router start up or routing process
-When there is a change in topology
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Chapter 1 11 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Step 5: Constructing a Link State Topology
Routers use a database to construct a topology map ofthe network
Best path selected from topologyand placed in routing table
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Chapter 1 12 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Sample Exchange of LSPs
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Chapter 1 13 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Shortest Path First (SPF) Tree
Building a portion of the SPF treeProcess begins by examining R2s LSP information
-R1 ignores 1st LSP
Reason: R1 already knows its connected to R2
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Chapter 1 14 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Shortest Path First (SPF) Tree
Building a portion of the SPF tree-R1 uses 2nd LSP
Reason: R1 can create a link from R2 to R5.This information is added to R1s SPF tree
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Chapter 1 15 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Shortest Path First (SPF) Tree
Building a portion of the SPF tree-R1 uses 3rd LSP
Reason: R1 learns that R2 is connected to10.5.0.0/16.
This link is added to R1s SPF tree.
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Chapter 1 16 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Link-State Routing Path Determination
Determining the shortest path
The shortest path to a destination determined by adding thecosts & finding the lowest cost
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Chapter 1 17 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Link-State Routing Table
Once the SPF algorithm has determined the shortestpath routes, these routes are placed in the routingtable.
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Chapter 1 18 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Routing Protocols Comparison Table
Routing
protocol
Builds
Topologicalmap
Router can
independentlydetermine the
shortest path to
every network.
Convergence
A periodic/
event drivenrouting updates
Use
ofLSP
Distance
vector
No No Slow Generally No No
Link State Yes Yes Fast Generally Yes Yes
Advantages of a Link-State Routing Protocol
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Chapter 1 19 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Link-State Hardware Requirements
Memory requirements
Typically link state routing protocols use morememory
Processing Requirements
More CPU processing is required of link staterouting protocols
Bandwidth Requirements
Initial startup of link state routing protocols canconsume lots of bandwidth
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Link State Routing Protocols
Two link state routing protocols used for routing IP
-Open Shortest Path First (OSPF)
-Intermediate System-Intermediate System (IS-IS)