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 The Structured Model for addressing provids IP addresses with meaning, hierarchical, and planned.

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

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

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. Criteria for Using Static Vs. Dynamic Addressing IPv6 Dynamic addressing supports both static and dynamic addressing -Dynamic addressing is referred to as autoconfiguration Part 1: Stateful autoconfiguration method, hosts retrieve addresses and other information from a server set up with a database.

9. Criteria for Using Static Vs. Dynamic Addressing Part 2: Stateless autoconfiguration method, a hosts generates it’s own address using locally available information. This includes advertised information from routers. The process starts by generating a link-local address for an interface. This involves combining the well-known link- local prefix (FE80::/10) with a 64 bit interface identifier.

10. The Two Parts of an IP Address PrefixHost 32 Bits Prefix Length

11. 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

12. 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

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

14. 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

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

16. 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

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

18. 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

19. Private and Public Addresses Figure 6-1

20. Network Address Translation (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

21. Network Address Translation (NAT) Problem with Private Addressing Outsourcing network management responsibilities to an outside vendor. With private addressing, the internal networks are not advertised to the outside. NAT problems would occur handling network management protocols like Simple Network Management Protocol (SNMP).

22. Address use in the Enterprise Figure 6-3

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

24. 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 Determinations

25. 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

26. IP Subnet-Zero Under old IP subnetting rules, the all 0’s subnet was reserved for the network, and the all 1’s subnet was reserved for the broadcast. Over time, engineers found that the all 0’s subnet wasn’t really used and, if it could be handed out as a useable network, many IP addresses could be changed.

27. 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?

28. 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

29. 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?

30. 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

31. 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?

32. 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

33. 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

34. IP Address Classes Traditional routing, is known as classful routing. No information is transmitted about the prefix length. The hosts and router examine the first three bits of the IP address to determine its class. CIDR notation identifies the prefix length with a length field, followed by a slash. Example: 10.1.0.1/16 The prefix length is 16 bits long. The subnet mask is 255.255.0.0.

35. Classful IP Addressing ClassFirst First BytePrefixIntent Few BitsLength A01-126*8Very large networks B10128-19116Large networks C110192-22324Small networks D1110224-239NAIP multicast E1111240-255NAExperimental *Addresses starting with 127 are reserved for IP traffic local to a host.

36. ClassPrefixNumber of Addresses Lengthper Network A82 24 -2 = 16,777,214 B162 16 -2 = 65,534 C242 8 -2 = 254 Division of the Classful Address Space

37. 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

38. 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

39. Classless Addressing Classless routing protocols transmit a prefix length with the IP address. This allows classless routing protocols to group networks into one entry and use the prefix length to specify which networks are grouped. Classless routing protocols include RIPv2, EIGRP, OSPF, BGP, and IS-IS.

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

41. Addressing Hierarchy Figure 6-6 – Page 387

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

43. 172.16.0.0/14 Summarization First Octet in Decimal First Octet in binary 172 10101100 Second Octet in DecimalSecond Octet in Binary 16 000100 00 17 000100 01 18 000100 10 19 000100 11

44. 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

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

46. A Mobile Host Mobile Host is a host that moves from one network to another and has a statically defined IP address. The administrator can move a mobile host to another and configure a router with a host-specific route to specify that traffic for the host should be routed through that router. Classless routing protocols match the longest prefix. Example: 10.108.16.0/20 and 10.108.16.1/32

47. A Mobile Host Subnets 10.108.16.0 - 10.108.31.0 Router ARouter B Host 10.108.16.1

48. 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 IPv6

49. 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 IPv6 Features

50. 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 IPv6 Features (continued)

51. 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 IPv6 Address Format

52. 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. IPv6 Addresses

53. IPv6 Aggregatable Global Unicast Address Format FPFormat Prefix (001) TLA IDTop-Level Aggregation Identifier RESReserved for future use NLA IDNext-Level Aggregation Identifier SLA IDSite-Level Aggregation Identifier Interface IDInterface Identifier 3 13 8 24 16 64 bits FPTLA ID RESNLA ID SLA ID Interface ID Public topology Site Topology

54. Upgrading to IPv6 Dual stack Tunneling Translation

55. 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

56. Tunneling Figure 2-25

57. Translation Dual-stack and tunneling techniques manage the interconnection of IPv6 domains. For legacy equipment that will not be upgraded to IPv6 and for some deployment scenarios, techniques are available for connecting IPv4-only nodes to IPv6-only nodes, using translation, an extension of NAT techniques.

58. Guidelines for Assigning Names Names should be – Short – Meaningful – Unambiguous – Distinct – Case insensitive Avoid names with unusual characters – Hyphens, underscores, asterisks, and so on

59. Maps names to IP addresses Supports hierarchical naming – example: frodo.rivendell.middle-earth.com A DNS server has a database of resource records (RRs) that maps names to addresses in the server’s “zone of authority” Client queries server – Uses UDP port 53 for name queries and replies – Uses TCP port 53 for zone transfers Domain Name System (DNS)

60. DNS Details Client/server model Client is configured with the IP address of a DNS server – Manually or DHCP can provide the address DNS resolver software on the client machine sends a query to the DNS server. Client may ask for recursive lookup.

61. DNS Recursion A DNS server may offer recursion, which allows the server to ask other servers – Each server is configured with the IP address of one or more root DNS servers. When a DNS server receives a response from another server, it replies to the resolver client software. The server also caches the information for future requests. – The network administrator of the authoritative DNS server for a name defines the length of time that a non-authoritative server may cache information.

62. Summary Use a systematic, structured, top-down approach to addressing and naming Assign addresses in a hierarchical fashion Distribute authority for addressing and naming where appropriate IPv6 looms in our future

63. Review Questions Why is it important to use a structured model for addressing and naming? When is it appropriate to use IP private addressing versus public addressing? When is it appropriate to use static versus dynamic addressing? What are some approaches to upgrading to IPv6?

64. This Week’s Outcomes IP Addressing Static and Dynamic Assignment IPv6 IPv4 to IPv6 Transition Methods

65. Due this week 5-1 – Concept questions 4 1-5-1 – Network design project – Switches

66. Next week Read chapters 7 in Top-Down Network Design 6-1 – Concept questions 5 FranklinLive session 7

67. Q & A Questions, comments, concerns?