CCNA ITN Chapter 5: Subnetting IP Networks PDF

Chapter 5: Subnetting IP Networks Chapter 5 - Sections & Objectives  5.1 Subnetting an IPv4 Network Implement an IPv4 addressing scheme to enable end-to-end connectivity in a small to medium-sized business network. Explain how subnetting segments a network to enable better communi...

Chapter 5: Subnetting IP Networks Chapter 5 - Sections & Objectives  5.1 Subnetting an IPv4 Network Implement an IPv4 addressing scheme to enable end-to-end connectivity in a small to medium-sized business network. Explain how subnetting segments a network to enable better communication. Explain how to calculate IPv4 subnets for a /24 prefix. Explain how to calculate IPv4 subnets for a /16 and /8 prefix. Given a set of requirements for subnetting, implement an IPv4 addressing scheme. Explain how to create a flexible addressing scheme using variable length subnet masking (VLSM).  5.2 Addressing Schemes Given a set of requirements, implement a VLSM addressing scheme to provide connectivity to end users in a small to medium-sized network. Implement a VLSM addressing scheme. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 2 5.1 Subnetting an IPv4 Network © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 3 Network Segmentation Broadcast Domains  Devices use broadcasts in an Ethernet LAN to locate: Other devices - Address Resolution Protocol (ARP) which sends Layer 2 broadcasts to a known IPv4 address on the local network to discover the associated MAC address. Services – Dynamic Host Configuration Protocol (DHCP) which sends broadcasts on the local network to locate a DHCP server.  Switches propagate broadcasts out all interfaces except the interface on which it was received. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 4 Network Segmentation Problems with Large Broadcast Domains  Hosts can generate excessive broadcasts and negatively affect the network. Slow network operations due to the significant amount of traffic it can cause. Slow device operations because a device must accept and process each broadcast packet.  Solution: Reduce the size of the network to create smaller broadcast domains. These smaller network spaces are called subnets. One Broadcast Broadcast in Broadcast in Domain LAN 1 LAN 2 contained in contained in 1 subnet 1 subnet © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 5 Network Segmentation Reasons for Subnetting  Reduces overall network traffic and improves network performance.  Enables an administrator to implement security policies such as which subnets are allowed or not allowed to communicate together. Communicating between Networks Subnetting by Location Subnetting by Device Type © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 6 Subnetting an IPv4 Network Octet Boundaries Networks are most easily subnetted at the octet boundary of /8, /16, and /24  Prefix length and the subnet mask are different ways of identifying the network portion of an address.  Subnets are created by borrowing host bits for network bits.  More host bits borrowed, the more subnets that can be defined. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 7 Subnetting an IPv4 Network Classless Subnetting Subnetting a /24 Network Subnets can borrow bits from any host bit position to create other masks. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 8 Subnetting an IPv4 Network Subnetting example 1( 2 Subnets ) © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 9 Subnetting example 2 ( 4 Subnets ) © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 10 Subnetting example 2 (4 Subnets) © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 11 Subnetting an IPv4 Network Subnetting with the Magic Number  Magic number technique used to calculate subnets  Magic number is simply the place value of the last one in the subnet mask  /25 11111111.11111111.11111111.10000000 magic number = 128  /26 11111111.11111111.11111111.11000000 magic number = 64  /27 11111111.11111111.11111111.11100000 magic number = 32 © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 12 Subnetting example 3 ( 6 subnets) © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 13 Subnetting example 3 (6 subnets) © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 14 Subnetting an IPv4 Network Subnetting example 3 ( 6 subnets) © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 15 Subnetting an IPv4 Network Classless Subnetting Example © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 16 Subnetting an IPv4 Network Creating 2 Subnets  /25 Subnetting Topology © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 17 Subnetting an IPv4 Network Creating Two Equal-sized Subnets (/25) Create 2 Equal-sized Subnets from 192.168.1.0 /24  Subnet Mask - 11111111.11111111.11111111.10000000  Magic Number = 128  192.168.1.0 /25 (start at 0)  192.168.1.128 /25 (Add 128) © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 18 Subnetting an IPv4 Network Subnetting Formulas Calculate Number of Subnetting a /24 Network Subnets Formula © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 19 Subnetting an IPv4 Network Subnetting Formulas (Cont.) Calculate Number of Calculating the Number of Hosts Hosts Formula © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 20 Subnetting an IPv4 Network Creating 4 Subnets  /26 Subnetting Topology © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 21 Subnetting an IPv4 Network Creating 4 Subnets (Cont.)  /26 Subnetting Topology © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 22 Subnetting an IPv4 Network Creating 4 Subnets (Cont.)  /26 Subnetting Topology © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 23 Subnetting an IPv4 Network Creating Four Equal-sized Subnets (/26) Create 4 Equal-sized Subnets from 192.168.1.0 /24  Subnet Mask in Binary – 11111111.11111111.11111111.11000000  2^2 = 4 Subnets  Magic Number = 64  192.168.1.0 /26  192.168.1.64 /26  192.168.1.128 /26  192.168.1.192 /26 © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 24 Subnetting an IPv4 Network Creating Eight Equal-sized Subnets (/27) Create 8 Equal-sized Subnets from 192.168.1.0 /24  Borrow 3 bits – 11111111.11111111.11111111.11100000  Magic Number = 32  192.168.1.0 /27 (Start at 0)  192.168.1.32 /27 (Add 32 to previous network)  192.168.1.64 /27 (Add 32)  192.168.1.96 /27 (Add 32)  192.168.1.128 /27 (Add 32)  192.168.1.160 /27 (Add 32)  192.168.1.192 /27 (Add 32)  192.168.1.224 /27 (Add 32) © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 25 Subnetting IPv4 Network ( 100 Subnets ) © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 26 Subnetting IPv4 Network ( 100 Subnets ) © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 27 Subnetting IPv4 Network ( 100 Subnets ) © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 28 Subnetting a /16 and /8 Prefix Creating Subnets with a /16 prefix © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 29 Subnetting a /16 and /8 Prefix Creating 100 Subnets with a /16 prefix © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 30 Subnetting a /16 and /8 Prefix Calculating the Hosts © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 31 Subnetting a /16 and /8 Prefix Creating One Hundred Equal-sized Subnets  An enterprise network requires 100 equal-sized subnets starting from 172.16.0.0/16 New Subnet Mask 11111111.11111111.11111110.00000000 2^7 = 128 Subnets 2^9 = 512 hosts per subnet Magic Number = 2 172.16.0.0 /23 172.16.2.0 /23 172.16.4.0 /23 172.16.6.0 /23 … 172.16.254.0 /23 © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 32 Subnetting a /16 and /8 Prefix Creating 1000 Subnets with a /8 Network © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 33 Subnetting a /16 and /8 Prefix Creating 1000 Subnets with a /8 Network (Cont.) © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 34 Subnetting to Meet Requirements Subnetting Based on Host Requirements © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 35 Subnetting to Meet Requirements Subnetting Based On Network Requirements Host devices used by employees in the Engineering department in one network and Management in a separate network. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 36 Subnetting to Meet Requirements Network Requirement Example © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 37 Subnetting to Meet Requirements Network Requirement Example (Cont.) © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 38 Benefits of Variable Length Subnet Masking Traditional Subnetting Wastes Addresses © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 39 © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 40 Benefits of Variable Length Subnet Masking Variable Length Subnet Masks (VLSM) Traditional Subnets of Varying Sizes © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 41 Variable Length Subnet Masks (VLSM) © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 42 Variable Length Subnet Masks (VLSM) © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 43 Practice Variable Length Subnet Mask © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 44 © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 45 Practice Variable Length Subnet Mask © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 46 Benefits of Variable Length Subnet Masking Basic VLSM Basic Subnetting © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 47 Benefits of Variable Length Subnet Masking VLSM Basics  Basic VLSM Subnets do not have to be equal sizes, as long as their address ranges do not overlap. When creating subnets it is easier to work from larger to smaller. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 48 Benefits of Variable Length Subnet Masking VLSM in Practice © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 49 Benefits of Variable Length Subnet Masking VLSM Chart © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 50 Benefits of Variable Length Subnet Masking VLSM Example  Given the network 172.16.0.0 /23 = 2^9 hosts = 512 /23 creates subnets: 256+128+64+32+16+16 = 512 hosts needed 1 network for 200 hosts - 256 Address range 172.16.0.0 – 172.16.1.255 1 network for 100 hosts - 128 1 network for 50 hosts - 64 1 network for 25 hosts - 32 1 network for 10 hosts - 16 4 point-to-point networks for 2 hosts each – 4x4 = 16 172.16.1.248 /30 (4) 172.16.1.252 /30 (4) © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 51