Tài liệu giảng dạy CCNA - module 03 chapter 11-Advanced Routing Protocol Topics

Table of Content2 Classless Routing Protocols and Classless Routing... Route aggregation with VLSMKL Sydney 192.168.48.0/22 Upstream provider Upstream provider Route summarization reduce

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Module 03 Routing Protocol

Chapter 11 Advanced Routing Protocol Topics

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Table of Content

2 Classless Routing Protocols and Classless Routing

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1 Route Summarization and

Variable-Length Subnet Masks

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Issues with IP Addressing

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IP Addressing Solutions

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What is VLSM ?

 Subnet 172.16.14.0/24 is divided into smaller subnets (Sub-subnet) :

 Subnet with one mask at first (/27)

 Further subnet one of these subnets not used elsewhere (/30)

172.16.14.140/30

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VLSM 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

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When to use VLSM?

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Calculating subnets with VLSM

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Calculating subnets with VLSM (2)

Derived from the

172.16.33.0/26 Subnet

30-Bit Mask (2 Hosts)

172.16.33.12/30 172.16.33.8/30 172.16.33.4/30

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Exercise Calculating subnets with

VLSM

Using VLSMs, define appropriate subnets for addressing the

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Route aggregation with VLSM

KL Sydney

192.168.48.0/22

Upstream provider

Route summarization reduces routing table size by

aggregating routes to multiple networks into one

supernet

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Route summarization example

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S0 10.137

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2 CLASSLESS ROUTING

PROTOCOLS AND CLASSLESS

ROUTING

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Classless and Classful Routing

Protocols

 Classful routing protocols do not transmit the mask

information along with the subnet number

 Classless routing protocols do transmit mask information

They support some advanced features such as VLSM and

summarization

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Autosummarization

 When a router has interfaces in more than one Class A, B,

or C network, it advertises a single route for an entire Class

A, B, or C network into the other network This feature is

called autosummarization

 When advertised on an interface whose IP address is not in

network X, routes related to subnets in network X are

summarized and advertised as one route That route is for

the entire Class A, B, or C network X

 Classful routing protocols perform autosummarization by

default

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Subnet mask: 255.255.255.0

10.3.4.0 10.3.5.0 10.3.6.0 10.3.7.0 172.16.3.0

172.16.1.0

I only know about

network 10.0.0.0 –

No subnets!

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Autosummarization Pitfalls

10.3.4.0 10.3.5.0 10.3.6.0 10.3.7.0 172.16.3.0

172.16.1.0

Which route to network 10.0.0.0

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Default route

Rest Net

Frame Relay 168.13.100.0

168.13.100.1

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Ip route command

R1(config)# ip route 0.0.0.0 0.0.0.0 168.13.1.101

R1 # show ip route

Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP

D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP

i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area

* - candidate default, U - per-user static route, o - ODR

P - periodic downloaded static route

Gateway of last resort is 168.13.1.101 to network 0.0.0.0

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Ip route command (cont.)

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Ip default-network command

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Classless Routing

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 10.1.1.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max =

84/89/114 ms

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 168.13.200.1, timeout is 2

seconds:

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Classless routing (cont.)

routing; there is a match.

route in this case, so I discard the packet.

3 I use the default route only if there is not a more specific match

Because there is no match, I use the default route.

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Summary

 Route summarization

 Variable-length subnet masking

 Classless and classful routing protocols—With classful routing

protocols, the routing protocol must consider class rules; classless routing

protocols do not Specifically, classful routing protocols must automatically

summarize routing information at network boundaries, meaning that they

cannot support discontiguous networks Classful routing protocols also

cannot support VLSM Classless routing protocols can support

discontiguous networks, and support VLSM.

 Classless and classful routing—With classful routing, the only time the

default route is used is when a packet’s destination Class A, B, or C

network number is not in the routing table With classless routing, the

default is used whenever the packet does not match a more specific route

in the routing table.

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