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ITEC 275 Computer Networks – Switching, Routing, and WANs

ITEC 275 Computer Networks – Switching, Routing, and WANs. Week 6 Robert D’Andrea. Some slides provide by Priscilla Oppenheimer and used with permission. Agenda. Learning Activities IP Addressing Static and Dynamic Assignment IPv6 IPv4 to IPv6 Transition Methods.

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ITEC 275 Computer Networks – Switching, Routing, and WANs

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  1. ITEC 275 Computer Networks – Switching, Routing, and WANs Week 6 Robert D’Andrea Some slides provide by Priscilla Oppenheimer and used with permission

  2. Agenda • Learning Activities • IP Addressing • Static and Dynamic Assignment • IPv6 • IPv4 to IPv6 Transition Methods

  3. Guidelines for Addressing and Naming • Use a structured model for addressing and naming • Assign addresses and names hierarchically • Decide in advance if you will use • Central or distributed authority for addressing and naming • Public or private addressing • Static or dynamic addressing and naming

  4. Advantages of Structured Models for Addressing & Naming • It makes it easier to • Read network maps • Operate network management software • Recognize devices in protocol analyzer traces • Meet goals for usability • Design filters on firewalls and routers • Implement route summarization

  5. Public IP Addresses • Managed by the Internet Assigned Numbers Authority (IANA) • Users are assigned IP addresses by Internet service providers (ISPs). • ISPs obtain allocations of IP addresses from their appropriate Regional Internet Registry (RIR)

  6. Regional Internet Registries (RIR) • American Registry for Internet Numbers (ARIN) serves North America and parts of the Caribbean. • RIPE Network Coordination Centre (RIPE NCC) serves Europe, the Middle East, and Central Asia. • Asia-Pacific Network Information Centre (APNIC) serves Asia and the Pacific region. • Latin American and Caribbean Internet Addresses Registry (LACNIC) serves Latin America and parts of the Caribbean. • African Network Information Centre (AfriNIC) serves Africa.

  7. Criteria for Using Static Vs. Dynamic Addressing • The number of end systems • The likelihood of needing to renumber • The need for high availability • Security requirements • The importance of tracking addresses • Whether end systems need additional information • (DHCP can provide more than just an address)

  8. The Two Parts of an IP Address 32 Bits Prefix Host Prefix Length

  9. Prefix Length • An IP address is accompanied by an indication of the prefix length • Subnet mask • /Length • Examples • 192.168.10.1 255.255.255.0 • 192.168.10.1/24

  10. Subnet Mask • 32 bits long • Specifies which part of an IP address is the network/subnet field and which part is the host field • The network/subnet portion of the mask is all 1s in binary. • The host portion of the mask is all 0s in binary. • Convert the binary expression back to dotted-decimal notation for entering into configurations. • Alternative • Use slash notation (for example /24) • Specifies the number of 1s

  11. Subnet Mask Example • 11111111 11111111 11111111 00000000 • What is this in slash notation? • What is this in dotted-decimal notation?

  12. Subnet Mask Example • 11111111 11111111 11111111 00000000 • What is this in slash notation? • /24 • What is this in dotted-decimal notation? • 255.255.255.0

  13. Another Subnet Mask Example • 11111111 11111111 11110000 00000000 • What is this in slash notation? • What is this in dotted-decimal notation?

  14. Another Subnet Mask Example • 11111111 11111111 11110000 00000000 • What is this in slash notation? • /20 • What is this in dotted-decimal notation? • 255.255.240.0

  15. One More Subnet Mask Example • 11111111 11111111 11111000 00000000 • What is this in slash notation? • What is this in dotted-decimal notation?

  16. One More Subnet Mask Example • 11111111 11111111 11111000 00000000 • What is this in slash notation? • 21 • What is this in dotted-decimal notation? • 255.255.248.0

  17. Private and Public Addresses Figure 6-1

  18. NAT • Static • One private address to one public address • Used for servers that must be visible to the public network • Dynamic • Many unregistered addresses to one registered address from a pool of addresses • Used for workstations that only connect to the public network when required • Combination • Used by most organizations

  19. NAT Demonstration Internet Protocol, SrcAddr: 192.168.0.8 (192.168.0.8), DstAddr: 207.46.249.189 (207.46.249.189) Version: 4 Header length: 20 bytes Differentiated Services Field: 0x00 (DSCP 0x00: Default; ECN: 0x00) 0000 00.. = Differentiated Services Codepoint: Default (0x00) .... ..0. = ECN-Capable Transport (ECT): 0 .... ...0 = ECN-CE: 0 Total Length: 295 Identification: 0x9a25 (39461) Flags: 0x04 .1.. = Don't fragment: Set ..0. = More fragments: Not set Fragment offset: 0 Time to live: 128 Protocol: TCP (0x06) Header checksum: 0xd60e (correct) Source: 192.168.0.8 (192.168.0.8) Destination: 207.46.249.189 (207.46.249.189) Transmission Control Protocol, Src Port: 1137 (1137), Dst Port: 80 (80), Seq: 1, Ack: 1, Len: 255 Source port: 1137 (1137) Destination port: 80 (80) Sequence number: 1

  20. Address use in the Enterprise Figure 6-3

  21. Designing Networks with Subnets • Determining subnet size • Computing subnet mask • Computing IP addresses

  22. Determinations • How many locations? • How many segments are required? • How many devices? • How large must each segment be? • What are the IP addressing requirements for each location? • Is public access required? • What subnet size is appropriate? • Determined by first and second questions

  23. Addresses to Avoid When Subnetting • A node address of all ones (broadcast) • A node address of all zeros (network) • A subnet address of all ones (all subnets) • A subnet address of all zeros (confusing) • Cisco IOS configuration permits a subnet address of all zeros with the ip subnet-zero command

  24. Practice • Network is 172.16.0.0 • You want to divide the network into subnets. • You will allow 600 nodes per subnet. • What subnet mask should you use? • What is the address of the first node on the first subnet? • What address would this node use to send to all devices on its subnet?

  25. Practice • Network is 172.16.0.0 • You want to divide the network into subnets. • 64 • You will allow 600 nodes per subnet. • 1022 • What subnet mask should you use? • 255.255.252.0 (/22) • What is the address of the first node on the first subnet? • 172.16.0.1 • What address would this node use to send to all devices on its subnet? • 172.16.3.255

  26. More Practice • Network is 172.16.0.0 • You have eight LANs, each of which will be its own subnet. • What subnet mask should you use? • What is the address of the first node on the first subnet? • What address would this node use to send to all devices on its subnet?

  27. More Practice • Network is 172.16.0.0 • You have eight LANs, each of which will be its own subnet. • What subnet mask should you use? • 255.255.224.0 (/19) • What is the address of the first node on the first subnet? • 172.16.0.1 • What address would this node use to send to all devices on its subnet? • 172.16.31.255

  28. One More • Network is 192.168.55.0 • You want to divide the network into subnets. • You will have approximately 25 nodes per subnet. • What subnet mask should you use? • What is the address of the last node on the last subnet? • What address would this node use to send to all devices on its subnet?

  29. One More • Network is 192.168.55.0 • You want to divide the network into subnets. • 8 • You will have approximately 25 nodes per subnet. • 30 • What subnet mask should you use? • 255.255.255.224 (/27) • What is the address of the last node on the last subnet? • 192.168.255.254 • What address would this node use to send to all devices on its subnet? • 192.168.255.255

  30. IP Address Classes • Classes are now considered obsolete • But you have to learn them because • Everyone in the industry still talks about them! • You may run into a device whose configuration is affected by the classful system

  31. Classful IP Addressing Class First First Byte Prefix Intent Few Bits Length A 0 1-126* 8 Very large networks B 10 128-191 16 Large networks C 110 192-223 24 Small networks D 1110 224-239 NA IP multicast E 1111 240-255 NA Experimental *Addresses starting with 127 are reserved for IP traffic local to a host.

  32. Division of the Classful Address Space Class Prefix Number of Addresses Length per Network A 8 224-2 = 16,777,214 B 16 216-2 = 65,534 C 24 28-2 = 254

  33. Classful IP is Wasteful • Class A uses 50% of address space • Class B uses 25% of address space • Class C uses 12.5% of address space • Class D and E use 12.5% of address space

  34. Classless Addressing • Prefix/host boundary can be anywhere • Less wasteful • Supports route summarization • Also known as • Aggregation • Supernetting • Classless routing • Classless inter-domain routing (CIDR) • Prefix routing

  35. Supernetting 172.16.0.0 • Move prefix boundary to the left • Branch office advertises 172.16.0.0/14 172.17.0.0 172.18.0.0 Branch-Office Router 172.19.0.0 Enterprise Core Network Branch-Office Networks

  36. Addressing Hierarchy Figure 6-6 – Page 387

  37. Route summarization • Summary 192.168.0/21 Figure 6-5 – Page 386

  38. 172.16.0.0/14 Summarization Second Octet in Decimal Second Octet in Binary 16 00010000 17 00010001 18 00010010 19 00010011

  39. Private Addressing • 10.0.0.0 – 10.255.255.255 • 172.16.0.0 – 172.31.255.255 • 192.168.0.0 – 192.168.255.255

  40. Discontiguous Subnets Area 0 Network 192.168.49.0 Router A Router B Area 1 Subnets 10.108.16.0 - 10.108.31.0 Area 2 Subnets 10.108.32.0 - 10.108.47.0

  41. A Mobile Host Router A Router B Subnets 10.108.16.0 - 10.108.31.0 Host 10.108.16.1

  42. IPv6 • A technology developed to overcome the limitations of the current standard, IPv4 • Combines expanded addressing with a more efficient and feature-rich header to improve scaling • Satisfies the increasingly complex requirements of hierarchical addressing that IPv4 does not support

  43. IPv6 Features • Larger address space: • IPv6 addresses are 128 bits, compared to IPv4's 32 bits • Allows more support for addressing hierarchy levels • A much greater number of addressable nodes • Simpler auto-configuration of addresses • Globally unique IP addresses: • Every node can have a unique global IPv6 address • Eliminates the need for NAT. • Site multi-homing: • IPv6 allows hosts to have multiple IPv6 addresses • Allows networks to have multiple IPv6 prefixes • Sites can have connections to multiple ISPs without breaking the global routing table

  44. IPv6 Features (continued) • Header format efficiency: • A simplified header with a fixed header size makes processing more efficient. • Improved privacy and security: • IPsec is the IETF standard for IP network security, available for both IPv4 and IPv6. Although the functions are essentially identical in both environments, IPsec is mandatory in IPv6. IPv6 also has optional security headers. • Flow labeling capability: • A new capability enables the labeling of packets belonging to particular traffic flows for which the sender requests special handling, such as nondefault quality of service (QoS) or real-time service. • Increased mobility and multicast capabilities: • Mobile IPv6 allows an IPv6 node to change its location on an IPv6 network and still maintain its existing connections. With Mobile IPv6, the mobile node is always reachable through one permanent address. A connection is established with a specific permanent address assigned to the mobile node, and the node remains connected no matter how many times it changes locations and addresses

  45. IPv6 Address Format • The format is x:x:x:x:x:x:x:x, where x is a 16-bit hexadecimal field • 2035:0001:2BC5:0000:0000:087C:0000:000A • Leading 0s within each set of four hexadecimal digits can be omitted, and a pair of colons (::) can be used, once within an address, to represent any number of successive 0s. • 2035:1:2BC5::87C:0:A

  46. IPv6 Addresses • Link-local address: The host configures its own link-local address autonomously, using the link-local prefix FE80::0/10 and a 64-bit identifier for the interface, in an EUI-64 format. • Stateless autoconfiguration: A router on the link advertises—either periodically or at the host's request—network information, such as the 64-bit prefix of the local network and its willingness to function as a default router for the link. Hosts can automatically generate their global IPv6 addresses by using the prefix in these router messages; the hosts do not need manual configuration or the help of a device such as a DHCP server. • Stateful using DHCP for IPv6 (DHCPv6): DHCPv6 is an updated version of DHCP for IPv4. DHCPv6 gives the network administrator more control than stateless autoconfiguration and can be used to distribute other information, including the address of the DNS server. DHCPv6 can also be used for automatic domain name registration of hosts using a dynamic DNS server. DHCPv6 uses multicast addresses.

  47. IPv6 Aggregatable Global Unicast Address Format • FP Format Prefix (001) • TLA ID Top-Level Aggregation Identifier • RES Reserved for future use • NLA ID Next-Level Aggregation Identifier • SLA ID Site-Level Aggregation Identifier • Interface ID Interface Identifier 3 13 8 24 16 64 bits FP TLA ID RES NLA ID SLA ID Interface ID Site Topology Public topology

  48. Upgrading to IPv6 • Dual stack • Tunneling • Translation

  49. Dual-Stack A dual-stack node enables both IPv4 and IPv6 stacks. Applications communicate with both IPv4 and IPv6 stacks; the IP version choice is based on name lookup and application preference. This is the most appropriate method for campus and access networks during the transition period, and it is the preferred technique for transitioning to IPv6. A dual-stack approach supports the maximum number of applications. Figure 6-24

  50. Tunneling Figure 2-25

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