Computer Networks: Addressing and Naming Guidelines
Addressing and naming guidelines in computer networks are crucial for efficient management. Learn about structured models, advantages, public IP addresses, and Regional Internet Registries. Understand hierarchical organization, IPv6 transition methods, SNMP monitoring, and more.
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ITEC 275 Computer Networks Switching, Routing, and WANs Week 6 Robert D Andrea Fall 2017
Administrative Midterm Exam The midterm exam will be administered the this week, October 9 through 14, 2017.
Agenda Learning Activities IP Addressing Hierarchical structure Static and Dynamic Assignment IPv6 IPv4 to IPv6 Transition Methods SNMP Monitoring
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)
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.
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)
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.
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
IPv4 Address Classes Classes Range CIDR Subnet Mask A 1 126 /8 255.0.0.0 B 128 - 191 /16 255.255.0.0 C 192 - 223 /24 255.255.255.0 D 224 239 N/A Multicast E 240 255 N/A Future use
Private IPv4 Addresses No. of addresses Start End 24-bit block (/8 prefix, 1 A) 10.0.0.0 10.255.255.255 16777216 20-bit block (/12 prefix, 16 B) 172.16.0.0 172.31.255.255 1048576 16-bit block (/16 prefix, 256 C) 192.168.0.0 192.168.255.255 65536
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: 11100000 - 224 - Class D has IP address rage from 224.0.0.0 to 239.255.255.255. 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. 11101111 239
IPv4 Address Class E IPv4's class E network (240.0.0.0/4) 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 researchers were not sure if there was enough time to develop IPv6 before we would run out of addresses. Why didn't they free up this block?
IPv4 Address Class E Is there any chance the Class E block of 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.
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 00000000 = 0 01111111 = 127
IPv4 Addresses Class Bits Class B 10000000 = 128 10111111 = 191 Class C 11000000 = 192 11011111 = 223
IPv4 Addresses Caveats 1. Network ID zero is always reserved as the universal gateway 2. IP addresses 127.0.0.0 127.255.255.255 is considered loopback. IP address 127.0.0.1 address is most commonly used address for loopback. 3. Private IP addresses are not routable on the Internet.
Parts of an IPv4 Address 32 Bits Prefix Host Prefix Length
Prefix Length IPv4 address are accompanied by an indication of the prefix length Classful dotted-decimal notation subnet mask 192.168.55.1 255.255.255.0 Classless Inter Domain Routing (CIDR) / Length 192.168.55.1/24
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
IPv4 Address Subnet Notation Classless Inter Domain Routing (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 would be 255.255.0.0.
Shorthand Subnet Mask Decimal Shorthand 128 192 224 240 248 252 254 255 The shorthand notations represent how many bits are used in the subnet mask. The minimum subnet mask for a Class C address must be 255.255.255.0, which is 24 bits (8 bits in each octet), or CIDR notation /24. Binary 10000000 11000000 11100000 11110000 11111000 11111100 11111110 11111111 CIDR /25 /26 /27 /28 /29 /30 /31 /32
Shorthand Subnet Mask Available subnets Usable hosts per subnet Total Prefix size Network mask usable hosts /24 255.255.255.0 1 254 254 /25 255.255.255.128 2 126 252 /26 255.255.255.192 4 62 248 /27 255.255.255.224 8 30 240 /28 255.255.255.240 16 14 224 /29 255.255.255.248 32 6 192 /30 255.255.255.252 64 2 128 2* /31 255.255.255.254 128 256
Shorthand Subnet Mask * The prefix size /31, is only achievable when using a point-to-point type network connection.
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
Subnet Mask Example 11111111 11111111 11111111 00000000 What is this in slash notation? What is this in dotted-decimal notation?
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
Subnet Mask Example 11111111 11111111 11110000 00000000 What is this in slash notation? What is this in dotted-decimal notation?
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
One More Subnet Mask Example 11111111 11111111 11111000 00000000 What is this in slash notation? What is this in dotted-decimal notation?
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
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 192.168.0.0 through 192.168.0.255 (192.168.0.0/24 block).
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
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.
Address Usage in the Enterprise Figure 6-3
Classful IP Addressing Class First Few Bits First Byte Prefix Length Intent A B C D E 0 10 110 1110 1111 1-126* 128-191 192-223 224-239 240-255 8 16 24 NA NA Very large networks Large networks Small networks IP multicast Future use *Addresses starting with 127 are reserved for IP traffic local to a host.
Division of the Classful Address Space Class Prefix Length Number of Addresses per Network A B C 8 16 24 224-2 = 16,777,214 216-2 = 65,534 28-2 = 254
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.
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
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.
Classful and Classless Protocols When to use RIPv2? RIP and RIPv1: R1(config)#router rip R1(config-router)#network 10.0.0.0 R1(config-router)#network 192.168.1.0 RIP v2 R1(config)#router rip R1(config-router)#version 2 R1(config-router)#network 10.0.0.0 R1(config-router)#network 192.168.1.0
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.
Definitions Subnetting a Class C Address 192.168.10.0 with subnet mask 255.255.255.240 Subnets? 240 (11110000)2^4 -2=14 Hosts? Four host bits, or 2^4 2=14 Valid subnets? 256 240 = 16 16 + 16 = 32, 32 + 16=48, 48 + 16=64, and 240. Valid subnets are 16,32, 48, 64, 224.
Definitions Subnetting a Class C Address Broadcast address for each subnet? Valid hosts? Subnet 16 32 48 64 80 96 112 224 First host 17 33 49 65 81 97 113 225 Last host 30 46 62 78 94 110 126 238 Broadcast 31 47 63 79 95 111 127 239
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.
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. information gathered from LSAs. Topological database A topological database is a collection of (SPF) algorithm is a calculation performed on the database resulting in the SPF tree. SPF algorithm (Dijkstra algorithm) The shortest path first Routing tables A list of the known paths and interfaces.
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.
Supernetting 172.16.0.0 172.17.0.0 172.18.0.0 Branch-Office Router 172.19.0.0 Enterprise Core Network Branch-Office Networks Move prefix boundary to the left Branch office advertises 172.16.0.0/14
Addressing Hierarchy Figure 6-6 Page 387
Route summarization Summary 192.168.0/21 Figure 6-5 Page 386
