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CCNA Discovery 3 - Chapter 4

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CCNA Discovery 3 - Chapter 4

  1. 1. Addressing in an Enterprise Network Introducing Routing and Switching in the Enterprise – Chapter 4Version 4.0 © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 1
  2. 2. Objectives Analyze the features and benefits of a hierarchical IP addressing structure. Plan and implement a VLSM IP addressing scheme. Plan a network using classless routing and CIDR. Configure and verify both static and dynamic NAT. © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 2
  3. 3. Features & Benefits of a Hierarchical IP Addressing Structure Flat networks with a single broadcast domain lose efficiency as hosts are added Two solutions: Create VLANs Use routers in a hierarchical network design © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 3
  4. 4. Features & Benefits of a Hierarchical IP Addressing Structure Classful network address in the Core Layer Successively smaller subnets in the Distribution and Access Layers © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 4
  5. 5. Features & Benefits of a Hierarchical IP Addressing StructureUse subnetting to subdivide a network based on: Physical location or logical grouping Application and security requirements Broadcast containment Hierarchical network design © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 5
  6. 6. Plan / Implement a VLSM Addressing Scheme Subnet mask: 32-bit value Distinguishes between network and host bits Can vary in length to accommodate number of hosts on LAN segment © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 6
  7. 7. Plan / Implement a VLSM Addressing Scheme Boolean ANDing compares bits in host address to bits in subnet mask 1 and 1 = 1 1 or 0 and 0 = 0 Resulting value is network address © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 7
  8. 8. Plan / Implement a VLSM Addressing SchemeSteps in basic subnetting: Borrow bits from the host side Add them to the network side Change mask to reflect additional bits © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 8
  9. 9. Plan / Implement a VLSM Addressing SchemeElements of an addressing scheme: Subnet number Network address Host range Broadcast address © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 9
  10. 10. Plan / Implement a VLSM Addressing SchemeBenefits of Variable Length Subnet Masks (VLSM): Flexibility Efficient use of address space Ability to use route summarization © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 10
  11. 11. Plan / Implement a VLSM Addressing Scheme Apply masks from largest group to smallest Avoid assigning addresses that are already allocated Allow for some growth in numbers of hosts on each subnet © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 11
  12. 12. Plan a Network Using Classless Routing and CIDRClassful routing Classless routing Default subnet masks  Network prefix Class determined by first  Slash (/) mask octet  Subnet mask information No subnet mask exchanged in routing information exchanged in updates routing updates © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 12
  13. 13. Plan a Network Using Classless Routing and CIDR Classless Inter-Domain Routing (CIDR) Uses address space efficiently Used for network address aggregation or summarizing © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 13
  14. 14. Plan a Network Using Classless Routing and CIDRRoute summarization: Use single address to represent group of contiguous subnets Occurs at network boundary Smaller routing table, faster lookups © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 14
  15. 15. Plan a Network Using Classless Routing and CIDR Discontiguous subnets cause unreliable routing Avoid separating subnets with a different network © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 15
  16. 16. Plan a Network Using Classless Routing and CIDR Use routing protocols that support VLSM Plan subnetting to complement hierarchical design Disable auto-summarization if necessary Update router IOS Allow for future growth © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 16
  17. 17. Configure and Verify Static and Dynamic NAT RFC 1918: private IP address space Routed internally, never on the Internet “Hides” internal addresses from other networks © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 17
  18. 18. Configure and Verify Static and Dynamic NAT Network Address Translation (NAT) NAT translates internal private addresses into one or more public addresses Use on boundary routers © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 18
  19. 19. Configure and Verify Static and Dynamic NAT Static NAT: map single inside local address to single public address Dynamic NAT: use a pool of public addresses to assign as needed © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 19
  20. 20. Configure and Verify Static and Dynamic NAT Port Address Translation (PAT) Dynamically translate multiple inside local addresses to one public address © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 20
  21. 21. Summary Hierarchical network design groups users into subnets VLSM enables different masks for each subnet VLSM requires classless routing protocols CIDR network addresses are determined by prefix length Route summarization, route aggregation, or supernetting, is done on a boundary router NAT translates private addresses into public addresses that route over the Internet PAT translates multiple local addresses into a single public address © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 21
  22. 22. © 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 22

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