ITEC 275 Computer Networks – Switching, Routing, and WANs Week 6 Robert D’Andrea 2015

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 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)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. 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)

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 ClassesRangeCIDRSubnet Mask A1 – 126/ B / C / D224 – 239N/AMulticast E240 – 255N/A

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

IPv4 Addresses Class Bits 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. Class A = = 127

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

IPv4 Addresses Caveats 1.Network ID zero is always reserved as the universal gateway 2.IP addresses – is considered loopback. IP address address is most commonly used address for loopback. 3.Private IP addresses are not routable on the Internet.

Parts of an IPv4 Address PrefixHost 32 Bits Prefix Length

An IPv4 address is accompanied by an indication of the prefix length Classful dotted-decimal notation subnet mask Classless Inter Domain Routing (CIDR) / Length /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: /16 The prefix length is 16 bits long. The subnet mask is

Shorthand Subnet Mask BinaryDecimalShorthandCIDR / / / / / / / /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 /24.

Shorthand Subnet Mask Prefix sizeNetwork mask Available subnets Usable hosts per subnet Total usable hosts / / / / / / / / * 256

Shorthand Subnet Mask * The prefix size /31, is only achievable with 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 What is this in slash notation? What is this in dotted-decimal notation?

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

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

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

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

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

Private and Public Addresses

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).

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 ClassFirst First BytePrefixIntent Few BitsLength A01-126*8Very large networks B Large networks C Small networks D NAIP multicast E NAExperimental *Addresses starting with 127 are reserved for IP traffic local to a host.

ClassPrefixNumber of Addresses Lengthper Network A = 16,777,214 B = 65,534 C = 254 Division of the Classful Address Space

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.

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.

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

Addressing Hierarchy Figure 6-6 – Page 387

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

/14 Summarization First Octet in Decimal First Octet in binary Second Octet in DecimalSecond Octet in Binary

Dis-contiguous Subnets Area 1 Subnets Area 0 Network Area 2 Subnets Router ARouter B

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.

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

A Mobile Host Subnets Router ARouter B Host

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 Addressing

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 Address Features

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. 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. 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)

IPv6 Dynamic addressing supports both static and dynamic addressing Dynamic addressing is referred to as auto-configuration and is made up of two components. Part 1: Stateful auto-configuration method, hosts retrieve addresses and other information from a server set up with a database. Part 2: Stateless auto-configuration 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. IPv6 Features (continued)

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 replaced with a pair of colons (::), once within an address, to represent any number of successive 0s. – 2035:1:2BC5::87C:0:A IPv6 Address Format

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 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. 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. 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. 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. 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. 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. IPv6 Addresses

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 bits FPTLA ID RESNLA ID SLA ID Interface ID Public topology Site Topology

Upgrading to IPv6 Dual stack Tunneling Translation

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.

Tunneling Figure 2-25

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.

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

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 Domain Name System (DNS)

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.

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.

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.

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 in many countries around the world. They are configured in the DNS root zone as 13 named authorities.

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

Root Server Website Who owns root? View:

Simple Network Management Protocol (SNMP) 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.

Simple Network Management Protocol (SNMP) 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.

SNMP Agent Computer Running SNMP Manager Requests Status Information from Devices Running SNMP Agent

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

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?

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

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

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

Q & A Questions, comments, concerns?