ccna3 m1 introduction classless routing
TRANSCRIPT
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CCNA – Semester3
Module 1Introduction to Classless Routing
Objectives
• Define VLSM and devide major network with VLSM
• Configure VLSM
• Differences between RIPv1 and RIPv2
• Configure RIPv2
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VLSM
Why VLSM?
• The addressing crisis
• Rapid increase in the size of routing tables
• IP address solutions:– Short term extensions to IPv4
– Subnetting 1985
– Variable length subnetting 1987
– Classless Interdomain Routing 1993
– Private IP address
– Network Address Translation(NAT)
– IPv6
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What is VLSM?
• With Variable-Length Subnet Masks (VLSM), a network administrator can use a long mask on networks with few hosts, and a short mask on subnets with many hosts
• In order to use VLSM, a network administrator must use a routing protocol that supports it:– OSPF– IS-IS– EIGRP– RIPv2– BGP– Static routing
VLSM
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A waste of space
• It has become acceptable practice to use the first and last subnets in a subnetted network in conjunction with VLSM.
• With ip subnet-zero command, network has 8 usable subnets.
Subnetting with VLSM
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Using VLSM
VLSM Practice
Subnet the network address 192.168.1.0/24
192.168.1.0/26
192.168.1.64/27
192.168.1.96/28 192.168.112.0/28
192.
168.
1.12
8/30
192.
168.
1.13
2/30
192.168.136.0/30
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Route aggregation with VLSM
• When using VLSM, try to keep the subnetworknumbers grouped together in the network to allow for aggregation.
• The use of Classless InterDomain Routing (CIDR) and VLSM not only prevents address waste, but also promotes route aggregation, or summarization.
Route Summarization
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Route Summarization
Route Summarization (Super network)
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Route Summarization Rules
• A router must know in detail the subnet numbers attached to it.
• A router does not need to tell other routers about each individual subnet if the router can send one aggregate route for a set of routers.
• A router using aggregate routes would have fewer entries in its routing table.
RIP version 2
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RIPv1 Limitations
• 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).
RIPv2
• RIP v2 is an improved version of RIP v1 and shares the following features: – It is a distance vector protocol that uses a hop count
metric.
– It uses holddown timers to prevent routing loops – default is 180 seconds.
– It uses split horizon to prevent routing loops.
– It uses 16 hops as a metric for infinite distance.
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RIPv2 vs. RIPv1
Configuring RIP v2
• The router command starts the routing process. The network command causes the implementation of the following three functions:– The routing updates are multicast out an interface. – The routing updates are processed if they enter that same
interface. – The subnet that is directly connected to that interface is
advertised.
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Configuring RIP v2
Verifying RIP Configuration
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IP Routing Table
Troubleshooting RIP v2
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Debug ip RIP output
Summary
• VLSM and the reasons for its use • Subnetting networks of different sizes using
VLSM • Route aggregation and summarization as they
relate to VLSM• Key features of RIP v1 and RIP v2 • Configuration of RIP v2 • Verifying and troubleshooting RIP v2 operation
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Lab Topology
14 IPs
20 IPs
CCNA3 – Module1