Chapter 10 -Vlsm

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Switching Basics and Switching Basics and Intermediate RoutingIntermediate Routing

CLASSLESS ROUTINGCLASSLESS ROUTING

TS, PHẠM VĂN TÍNHTS, PHẠM VĂN TÍNH

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ObjectivesObjectives•Define VLSM and briefly describe the reasons for its use •Divide a major network into subnets of different sizes using VLSM •Define route aggregation and summarization as they relate to VLSM •Configure a router using VLSM • Identify the key features of RIP v1 and RIP v2 • Identify the important differences between RIP v1 and RIP v2 •Configure RIP v2 •Verify and troubleshoot RIP v2 operation •Configure default routes using the ip route and ip default-network commands

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Variable-Length Subnet Masking Variable-Length Subnet Masking (VLSM)(VLSM)

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Issues with IP AddressingIssues with IP Addressing

• IP addressing crisis• As early as 1992, the IETF identified two

specific concerns:– IP address exhaustion–Routing table growth

U N I V E R S I T YU N I V E R S I T Y

Internet

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IP Addressing SolutionsIP Addressing Solutions

• Short term to extension to IPv4– Subneting masking: RFCs 950, 1812– Variable-Length Subnet Masks: RFC 1812 – Classless InterDomain Routing: RFCs 1518,

1519, 2050– Address allocation for private Internets: RFC

1918– Network Address Translation: RFC 1631– Route summarization: RFC 1518

• Ultimate solution: IPv6 128-bit address space

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What is VLSM ?What is VLSM ?

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VLSM is supportedVLSM is supported

• Open Shortest Path First (OSPF).• Integrated Intermediate System to

Intermediate System (Integrated IS-IS).• Enhanced Interior Gateway Routing

Protocol (EIGRP).• RIP v2.• Static routing.

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A waste of space A waste of space

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When to use VLSM? When to use VLSM?

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Sub - SubnetsSub - Subnets

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Calculating subnets with VLSM Calculating subnets with VLSM

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VLSM ExampleVLSM Example

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Calculating subnets with VLSMCalculating subnets with VLSM

192.168.10.0/24.

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Calculating subnets with VLSMCalculating subnets with VLSM

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Route aggregation with VLSMRoute aggregation with VLSM

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Route summarization exampleRoute summarization example

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Configuring VLSMConfiguring VLSM

60 Hosts 12 Hosts 12 Hosts

192.168.10.0/24

KL

SydneyPerth Singapore

192.168.10.64/27

192.168.10.128/30192.168.10.132/30

192.168.10.136/30

28 Hosts

192.168.10.0/26 192.168.10.96/28 192.168.10.112/28

S010.138

S0 10.137

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RIP Version 2RIP Version 2

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RIP v1: RIP v1: CharacteristicsCharacteristics • IGP protocol, is classful routing.• It is a distance vector protocol that uses a hop

count metric. • The maximum number of hops is 15. • By default, routing updates are broadcast every

30 seconds.• The router applies the one subnet mask that is

configured on the receiving interface to receive network information.

• Load balancing over as many as six equal-cost paths, with four paths as the default.

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RIP v1: RIP v1: LimitationsLimitations

• It does not send subnet mask information in its updates.

• It sends updates as broadcasts on 255.255.255.255.

• It does not support authentication. • It is not able to support VLSM or classless

interdomain routing (CIDR).

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RIP v1: RIP v1: ConfigurationConfiguration

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RIP v2 features RIP v2 features

• Send out subnet mask information with the route update.

• Support VLSM or classless interdomain routing (CIDR).

• Provides for authentication in its updates.• Provides Multicast routing updates, using the

Class D address 224.0.0.9.• Use external route tags• Routing update is includes a next-hop route ip

address.

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Comparing RIP v1 and v2 Comparing RIP v1 and v2

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RIP v2: RIP v2: ConfigurationConfiguration

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Verifying RIP v2 : Verifying RIP v2 : SHOW IP PROTOCOLSSHOW IP PROTOCOLS

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Verifying RIP v2: Verifying RIP v2: SHOW IP ROUTESHOW IP ROUTE

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Troubleshooting RIP v2 : Troubleshooting RIP v2 : DEBUG IP RIPDEBUG IP RIP

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Default routes Default routes

InternetInternet

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Q&AQ&A

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