1. ITEC 275 Computer Networks – Switching, Routing, and WANs
Week 6
Robert D’Andrea
Winter 2017

2. Administrative Midterm Exam
The midterm exam will be administered the eighth week of the term, February 20 through 25, The midterm exam review has already be ed to the class. If you cannot locate your review, me.

3. Agenda Learning Activities IP Addressing Hierarchical structure
Static and Dynamic Assignment
IPv6
IPv4 to IPv6 Transition Methods
SNMP Monitoring

4. Guidelines for Addressing and Naming
Use a structured model for addressing and naming. A topology may be useful for viewing the hierarchy in the network and recognize address boundaries.
Assign addresses and names hierarchically
Decide in advance if you will use
Central or distributed authority for addressing and naming. Determine who is in charge of delegating addresses and naming conventions.
Public or private addressing (IANA or RFC 1918)
Static or dynamic addressing and naming (DHCP Dynamic Host Configuration Protocol)

5. Advantages of Structured Models for Addressing & Naming
Networks are easier to understand by
Reading network maps
Operating network management software
Recognize devices in protocol analyzer traces
Meeting goals for usability
Designing filters on firewalls and routers
Implementing route summarization
The Structured Model for addressing provides the IP address with meaning and hierarchical organization.

6. 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)
Internet Assigned Numbers Authority (IANA). IANA allocates IP addresses to the Regional Internet Registries (RIRs)

7. 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.

8. Static Vs. Dynamic Addressing
Bases for addressing criteria
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)

9. IPv4 Address Classes Classes Range CIDR Subnet Mask A 1 – 126 /8 B
/16 C
/24 D
224 – 239
N/A
Multicast E
240 – 255
Future use

10. Private IPv4 Addresses Start End No. of addresses
24-bit block (/8 prefix, 1 × A)
20-bit block (/12 prefix, 16 × B)
16-bit block (/16 prefix, 256 × C)
65536

11. IPv4 Address Class D
The first four bits of the first octet in Class D IP addresses are set to 1110, giving a range of: Class D has IP address rage from to Class D is reserved for Multicasting. In multicasting data is not destined for a particular host, that is why there is no need to extract host address from the IP address, and Class D does not have any subnet mask.

12. IPv4 Address Class E
IPv4's class E network ( /4) contains 268 million addresses. Despite the advertisements for IPv6, claiming we have ran out of address space, this block ironically still claims to be "Reserved for future use". Why hasn't this block been freed up yet?
Of course, IPv6 should be promoted instead of freeing up more IPv4 addresses, but we've seen the address shortage coming for years. There was a time when they we’ren’t sure there was enough time to develop IPv6 before we would run out of addresses. Why didn't they free up this block?

13. IPv4 Address Class E
And is there any chance these addresses will be used in the future, like when IPv6 is fairly widely implemented but we still need IPv4 for backwards compatibility? It will be phased out regardless, but then ISPs don't have to employ NAT for IPv4 compatibility.

14. IPv4 Addresses Class Bits
Traditional routing, also 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. Class A = = 127

15. IPv4 Addresses Class Bits
Class B = = 191 Class C = = 223

16. IPv4 Addresses Caveats
Network ID zero is always reserved as the universal gateway
IP addresses – is considered loopback. IP address address is most commonly used address for loopback.
Private IP addresses are not routable on the Internet.

17. Parts of an IPv4 Address
32 Bits
Prefix
Host
Prefix Length

18. Prefix Length
IPv4 address are accompanied by an indication of the prefix length
Classful dotted-decimal notation subnet mask
Classless Inter Domain Routing (CIDR) / Length
/24

19. IPv4 Address Subnet Notations
Subnet size 32 bits long (4 octets)
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 IPv4 address representation
Use slash notation (for example /24)
Specifies the number of 1s

20. IPv4 Address Subnet Notation
Classless Inter Domain Routing (CIDR) notation identifies the prefix length with a length field, followed by a slash. Example: /16 The prefix length is 16 bits long. The subnet mask would be

21. Shorthand Subnet Mask 10000000 128 /25 11000000 192 /26
Binary Decimal Shorthand CIDR
/25
/26
/27
/28
/29
/30
/31
/32
The shorthand notations represent how many bits are used in the subnet mask.
The minimum subnet mask for a Class C address must be , which is 24 bits (8 bits in each octet), or CIDR notation /24.

22. Usable hosts per subnet
Shorthand Subnet Mask
Prefix size
Network mask
Available subnets
Usable hosts per subnet
Total usable hosts
/24 1
254
/25 2
126
252
/26 4 62
248
/27 8 30
240
/28 16 14
224
/29 32 6
192
/30 64
128
/31
2 *
256

23. Shorthand Subnet Mask
* The prefix size /31, is only achievable when using a point-to-point type network connection.

24. Shorthand Subnet Mask 2^0 = 1 2^1 = 2 2^2 = 4 2^3 = 8 2^4 = 16
2^5 = 32
2^6 = 64
2^7 = 128
2^8 = 256

25. Subnet Mask Example
What is this in slash notation?
What is this in dotted-decimal notation?

26. Subnet Mask Example
What is this in slash notation?
/24
What is this in dotted-decimal notation?

27. Subnet Mask Example
What is this in slash notation?
What is this in dotted-decimal notation?

28. Subnet Mask Example
What is this in slash notation?
/20
What is this in dotted-decimal notation?

29. One More Subnet Mask Example
What is this in slash notation?
What is this in dotted-decimal notation?

30. One More Subnet Mask Example
What is this in slash notation? 21
What is this in dotted-decimal notation?

31. Private and Public Addresses

32. Private IPv4 Addresses
Caveat 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). Advantages with Private Addressing Any user may use any of the reserved blocks. Typically, a network administrator will divide a block into subnets; for example, many home routers automatically use a default address range of through ( /24 block).

33. Network Address Translation (NAT)
Static translations
One private address to one public address
Used for servers that must be visible to the public network
Dynamic translations
Many unregistered addresses to one registered address from a pool of addresses (similar to PBX)
Used for workstations that only connect to the public network when required
Combination of both translations
Used by most organizations

34. Network Address Translation (NAT)
Network Address Translation (NAT) is a methodology of modifying network address information in Internet Protocol (IP) datagram packet headers while they are in transit across a traffic routing device for the purpose of remapping one IP address space into another.

35. Address Usage in the Enterprise
Figure 6-3

36. Classful IP Addressing
Class First First Byte Prefix Intent
Few Bits Length
A * 8 Very large networks
B Large networks
C Small networks
D NA IP multicast
E NA Future use
*Addresses starting with 127 are reserved for IP traffic local to a host.

37. Division of the Classful Address Space
Class Prefix Number of Addresses
Length per Network
A = 16,777,214
B = 65,534
C = 254

38. Classless Addressing
If you assume that IP addresses do not need to have their default classful netmask and they can be sub-netted then you do have to specify sub-netmask. This is referred to as classless, because you don’t use a default classful mask.

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

40. 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.

41. Classful and Classless Protocols
When to use RIPv2? RIP and RIPv1: R1(config)#router rip R1(config-router)#network R1(config-router)#network RIP v2 R1(config)#router rip R1(config-router)#version 2 R1(config-router)#network R1(config-router)#network

42. Definitions
Sub-netting is when you take one large network and break it into a bunch of smaller networks.
A subnet mask is a 32-bit value that allows the recipient of IP packets to distinguish the network ID portion of the IP address from the host ID portion of the IP address.
The 1s in the subnet mask represent the position referred to as the network or subnet addresses.

43. Routing Protocols
Distance vector finds the best path to a remote network by judging distance. Each time the packet goes through a router, that’s called or considered a hop.
Link State, also called shortest path first protocols, the routers each create three separate tables. One to keep track of directly attached neighbors. A second table to determine the topology of the entire internetwork. The third table is used as a routing table.

44. Routing Protocols
Some important terms related with Link State Routing Protocols
•Link-state advertisements (LSAs) – A link-state advertisement (LSA) is a small packet of routing information that is sent between routers.
•Topological database – A topological database is a collection of information gathered from LSAs.
•SPF algorithm (Dijkstra algorithm) – The shortest path first (SPF) algorithm is a calculation performed on the database resulting in the SPF tree.
•Routing tables – A list of the known paths and interfaces.

45. Routing Protocols
With a Distance Vector protocol, the path or 'route' chosen would be from A to B directly over the ISDN serial link, even though that link is about 10 times slower than the indirect route from A to C to D to B.
A Link State protocol would choose the A to C to D to B path because it's using a faster medium (100 Mb Ethernet). In this example, it would be better to run a Link State routing protocol, but if all the links in the network are the same speed, then a Distance Vector protocol would be the best choice.

46. Enterprise Core Network Branch-Office Networks
Supernetting
Branch-Office Router
Enterprise Core Network
Branch-Office Networks
Move prefix boundary to the left
Branch office advertises /14

47. Addressing Hierarchy
Figure 6-6 – Page 387

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

49. /14 Summarization
First Octet in Decimal First Octet in binary
Second Octet in Decimal Second Octet in Binary

50. Dis-Continuous Subnets
Traditional classful IP addressing was assumed that subnets would be contiguous. What that means is basically that to get from one subnet of some major network to any other subnet of that network, you would go through only subnets of that network. For example if you were in subnet and you were going to you might go through That would be contiguous.

51. Dis-Continuous Subnets
Dis-contiguous subnets means that to go from one subnet of a network to another subnet of that network you must go through subnets of a different network. For example if you are in subnet and to get to you must go through then that would be dis-contiguous.

52. Dis-contiguous Subnets
Area 0
Network
Router A
Router B
Area 1
Subnets
Area 2
Subnets

53. Dis-contiguous Subnets
Router A advertises access to network Router B ignores the advertisement because it can already get to network This occurs in both directions with the routers. Classless routing protocol is one method for solving this problem.

54. Dis-contiguous Subnets

55. 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: /20 and /32

56. A Mobile Host Router A Router B Subnets 10.108.16.0 - 10.108.31.0

57. IPv6 Addressing
IPv6 is the new technology developed to overcome the limitations of the current standard, IPv4 addressing. 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.

58. IPv6 Address 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

59. 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.

60. IPv6 Features (continued)
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 non default quality of service (QoS) or real-time service.

61. IPv6 Features (continued)
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

62. IPv6 Features (continued)
IPv6 Dynamic addressing supports both static and dynamic addressing.
Dynamic addressing is referred to as auto-configuration and is made up of two components.
Component #1: Stateful auto-configuration method, hosts retrieve addresses and other information from a server set up with a database.
Component #2: Stateless auto-configuration method, a hosts generates it’s own address using locally available information.

63. IPv6 Features (continued)
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.

64. IPv6 Address Format
The format is x:x:x:x:x:x:x:x, where the x’s are 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 replaced with a pair of colons (::), once within an address, to represent any number of successive 0s.
2035:1:2BC5::87C:0:A

65. 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.
A link-local address is a network address that is valid only for communications within the network segment (link) or the broadcast domain that the host is connected to. Link-local addresses are usually not guaranteed to be unique beyond a single network segment.

66. IPv6 Addresses Link Local Prefix

67. IPv6 Addresses
A link-local address is a network address that is valid only for communications within the network segment (link) or the broadcast domain that the host is connected to. Link-local addresses are usually not guaranteed to be unique beyond a single network segment. Routers therefore do not forward packets with link-local addresses.

68. IPv6 Addresses
For protocols that have only link-local addresses, such as Ethernet, hardware addresses that the manufacturer delivers in network circuits are unique, consisting of a vendor identification and a serial identifier. Link-local addresses for IPv4 are defined in the address block /16, in CIDR notation. In IPv6, they are assigned with the fe80::/10 prefix.

69. IPv6 Addresses
The link-local address is useful in the context of a single link or network. IPv6 link-local addresses can be configured automatically on an interface. Link-local addresses serve as a way for connecting devices on the same local network without the need for globally unique addresses. A router utilizing IPv6 must not forward packets that have either link-local source or destination address.

70. IPv6 Addresses
Link-local addresses are used in neighbor discovery and in stateless auto-configuration process. Media access control (MAC) addresses are used in local broadcast networks, such as Ethernet which are link-local addresses. Such devices are configured with an address in hardware by the manufacturer.

71. IPv6 Addresses

72. IPv6 Addresses
Stateless auto-configuration: 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.

73. IPv6 Addresses
Stateful using DHCP for IPv6 (DHCPv6): DHCPv6 is an updated version of DHCP for IPv4. DHCPv6 gives the network administrator more control than stateless auto-configuration 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.

74. IPv6 Aggregatable Global Unicast Address Format
bits FP
TLA ID
RES
NLA ID
SLA ID
Interface ID
Site
Topology
Public topology
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

75. Upgrading to IPv6 Dual stack Tunneling Translation
Dual stack. Both IPv4 and IPv6 stacks run on the system. The system is able to communicate with both IPv6 and IPv4 devices. The choice of IP version is based on name lookup and application preference. This is the most appropriate for campus and access-layer networks during the transition period and is the preferred technique for transition to IPv6. Operating systems that support a dual stack include FreeBSD, Linux, Sun Solaris, and Windows 2000/XP.
Tunneling. This method encapsulates IPv6 packets for traversal across an IPv4 network. By using tunnels, isolated IPv6 networks can communicate without requiring an upgrade to the IPv4 infrastructure. Both routers and hosts can use tunneling.
Translation. This method translates one type of address to the other to facilitate communication between an IPv4 and an IPv6 network. Translation will mainly be used for legacy equipment that will not be upgraded to IPv6. An IPv6 node behind a translation device has full connectivity to other IPv6 nodes and has NAT functionality for communicating with IPv4 devices. Translation can be handled by Application Level Gateways (ALGs) or by an application programming interface (API) on every host. The two main translation solutions are NAT-Protocol Translation (NAT-PT) and Dual-Stack Transition Mechanism (DSTM).

76. 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.

77. Tunneling
Figure 2-25

78. 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.

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

80. Domain Name System (DNS)
Map 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

81. 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.

82. 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.

83. List of Root Servers a.root-servers.net
, 2001:503:ba3e::2:30
VeriSign, Inc.
b.root-servers.net
University of Southern California (ISI)
c.root-servers.net
, 2001:500:2::c
Cogent Communications
d.root-servers.net
, 2001:500:2d::d
University of Maryland
e.root-servers.net
NASA (Ames Research Center)
f.root-servers.net
, 2001:500:2f::f
Internet Systems Consortium, Inc.
g.root-servers.net
US Department of Defence (NIC)
h.root-servers.net
, 2001:500:1::803f:235
US Army (Research Lab)
i.root-servers.net
, 2001:7fe::53
Netnod
j.root-servers.net
, 2001:503:c27::2:30
k.root-servers.net
, 2001:7fd::1
RIPE NCC
l.root-servers.net
, 2001:500:3::42
ICANN
m.root-servers.net
, 2001:dc3::35
WIDE Project

84. DNS Root Zone
The DNS root zone is the top-level DNS zone in the hierarchical namespace of the Domain Name System (DNS) of the Internet.

85. DNS Root Servers
The authoritative name servers that serve the DNS root zone, commonly known as the “root servers”, are a network of hundreds of servers (more than 300) in many countries around the world. They are configured in the DNS root zone as 13 named authorities.

86. DNS Root Servers Who operates them?
The root servers are operated by 12 different organizations:
• Verisign
• University of Southern California
• Cogent
• University of Maryland
• NASA AMES Research Center
• Internet Systems Consortium
• US Department of Defense
• US Army Research Lab
• Netnod
• RIPE
• ICANN
• WIDE

87. DNS Root Servers Who operates them?
Many of these organizations have been operating root servers since the creation of the DNS; and the list shows the Internet’s early roots as a US-based research and military network.

88. DNS Root Zone

89. DNS Root Zone
Who owns root? View:

90. Simple Network Management Protocol
Enterprise networks are heterogeneous. In addition to multi-tiered applications, a critical part of the infrastructure consists of network devices and other applications that are vendor specific. However, these devices normally have a Simple Network Management Protocol (SNMP) agent (interface) and this facilitates SNMP monitoring.

91. Simple Network Management Protocol
What is SNMP?
SNMP stands for Simple Network Management Protocol and is an industry standard for the communication among devices in your IT infrastructure. It is used for collecting information from and sending configuration to devices such as servers, printers, hubs, switches, and routers in your network. SNMP lets you keep an eye on network and bandwidth usage and track important issues such as uptime and traffic levels.

92. Simple Network Management Protocol

93. 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
Review IPv4 and IPv6 addressing
IPv6 looms in our future

94. 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?

95. This Week’s Outcomes IP Addressing Static and Dynamic Assignment IPv4
IPv4 to IPv6 Transition Methods
Distant vector and Link State Protocol
SNMP
DNS Root Servers

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

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

98. Q & A
Questions, comments, concerns?