25.5_link-state and balanced hybrid routing
TRANSCRIPT
-
7/31/2019 25.5_Link-State and Balanced Hybrid Routing
1/12
2002, Cisco Systems, Inc. All rights reserved.
-
7/31/2019 25.5_Link-State and Balanced Hybrid Routing
2/12
2002, Cisco Systems, Inc. All rights reserved. ICND v2.05-2
2002, Cisco Systems, Inc. All rights reserved. 2
Link-State and BalancedHybrid Routing
-
7/31/2019 25.5_Link-State and Balanced Hybrid Routing
3/12
2002, Cisco Systems, Inc. All rights reserved. ICND v2.05-3
Objectives
Upon completing this lesson, you will beable to:
Describe the issues associated with link-staterouting and identify solutions to those issues
Describe the features of balanced hybrid routingprotocols
-
7/31/2019 25.5_Link-State and Balanced Hybrid Routing
4/12
2002, Cisco Systems, Inc. All rights reserved. ICND v2.05-4
After initial flood, pass small event-triggered link-state
updates to all other routers
Link-State Routing Protocols
-
7/31/2019 25.5_Link-State and Balanced Hybrid Routing
5/12
2002, Cisco Systems, Inc. All rights reserved. ICND v2.05-5
Minimizes routing table entries
Localizes impact of a topology change within
an area
Link-State Network Hierarchy Example
-
7/31/2019 25.5_Link-State and Balanced Hybrid Routing
6/12
2002, Cisco Systems, Inc. All rights reserved. ICND v2.05-6
Link-State RoutingProtocol Algorithms
-
7/31/2019 25.5_Link-State and Balanced Hybrid Routing
7/12 2002, Cisco Systems, Inc. All rights reserved. ICND v2.05-7
Benefits of Link-State Routing
Fast convergence: changes are reportedimmediately by the source affected.
Robustness against routing loops:Routers know the topology.
Link-state packets are sequenced andacknowledged.
By careful (hierarchical) network design, you canutilize resources optimally.
-
7/31/2019 25.5_Link-State and Balanced Hybrid Routing
8/12 2002, Cisco Systems, Inc. All rights reserved. ICND v2.05-8
Caveats of Link-State Routing
Significant demands for resources:
Memory (three tables: adjacency, topology,forwarding)
CPU (Dijkstras algorithm can be intensive, especiallywhen a lot of instabilities are present.)
Requires very strict network design (when more areasarea routing)
Problems with partitioning of areas
Configuration generally simple but can be complexwhen tuning various parameters and when the design iscomplex
Troubleshooting easier than in distance vector routing
-
7/31/2019 25.5_Link-State and Balanced Hybrid Routing
9/12 2002, Cisco Systems, Inc. All rights reserved. ICND v2.05-9
Drawbacks to Link-State RoutingProtocols
Initial discovery may cause flooding.
Memory- and processor-intensive.
-
7/31/2019 25.5_Link-State and Balanced Hybrid Routing
10/12 2002, Cisco Systems, Inc. All rights reserved. ICND v2.05-10
Shares attributes of both distance vectorand link-state routing
Balanced Hybrid Routing
-
7/31/2019 25.5_Link-State and Balanced Hybrid Routing
11/12 2002, Cisco Systems, Inc. All rights reserved. ICND v2.05-11
Summary
Link-state routing uses LSAs, a topologicaldatabase, the SPF algorithm, the resulting SPF tree,and a routing table of paths and ports to eachnetwork.
Link-state routing algorithms maintain a complexdatabase of the network's topology by exchangingLSAs with other routers in a network.
Link-state routing may flood the network with LSAs
during initial topology discovery and can be bothmemory- and processor-intensive.
Balanced hybrid routing protocols combine aspectsof both distance vector and link-state protocols.
-
7/31/2019 25.5_Link-State and Balanced Hybrid Routing
12/12