Week Nine • Attendance • Announcements Happy with the midterm exam scores Review question(s) on midterm exam • Final exam more questions and questions specific • Review Week Eight Information • Current Week Information • Upcoming Assignments
Midterm Exam Question Question 134 The first step in the design process should be predocumenting the design requirements and reviewing them with the customer for verification and approval, obtaining direct customer input, in either oral or written form. Identify the predocumenting procedures. Answer: Sifting, translating, processing, and reordering
Week Eight Topics • NAT Overload • CIDR • Classful and classful • IPv6 Standard • IPv6 Transition • Routing Protocols
IP Address Historical classful network architecture Class Leading address bits Range of first octet Format Network IDFormat Host IDFormat Number of networks Number of addresses Class A 0 0 - 127 a b.c.d 27 = 128 224 = 16777216 Class B 10 128 - 191 a.bc.d 214 = 16384 216 = 65536 Class C 110 192 – 223 a.b.c d 221 = 2097152 28 = 256 Fields defined below. • Leading address bits • Range of first octet • Network ID format • Host ID format • Number of networks • Number of addresses
IP Addresses Public • Fixed length: 32 bits • Initial classful structure (1981) • Total IP address size: 4 billion • Class A: 128 networks, 16M hosts • Class B: 16K networks, 64K hosts • Class C: 2M networks, 256 hosts
Network Address Translation (NAT) What is NAT Overload? NAT overloading (sometimes called Port Address Translation or PAT) maps multiple private IP addresses to a single public IP address or a few addresses.This is what most home routers do. With NAT overloading, multiple addresses can be mapped to one or to a few addresses because each private address is also tracked by a port number. When a client opens a TCP/IP session, the NAT router assigns a port number to its source address. NAT overload ensures that clients use a different TCP port number for each client session with a server on the Interne
Classless Interdomain Routing (CIDR) What is CIDR? CIDR is a new addressing scheme for the Internet which allows for more efficient allocation of IP addresses than the old Class A, B, and C address scheme. Why Do We Need CIDR? With a new network being connected to the Internet every 30 minutes the Internet was faced with two critical problems: Running out of IP addresses Running out of capacity in the global routing tables
Classless Inter-Domain Routing (CIDR) CIDR is pronounced “cider” With CIDR, addresses use bit identifiers, or bit masks, instead of an address class to determine the network portion of an address CIDR uses the /N notation instead of subnet masks CIDR allows for the more efficient allocation of IP addresses
Classless Inter-Domain Routing (CIDR) 172.16.0.0 255.255.0.0= 172.16.0.0 /16 18.104.22.168 255.255.255.0= 22.214.171.124 /24 Note that 192.168.24.0 /22 is not a Class C network, it has a subnet mask of 255.255.252.0
CIDR and Route Aggregation • CIDR allows routers to summarize, or aggregate, routing information • One address with a mask can represent multiple networks • This reduces the size of routing tables • Supernetting is another term for route aggregation
CIDR and Route Aggregation Given four Class C Networks (/24): 192.168.16.0 11000000 1010100000010000 00000000 192.168.17.0 11000000 1010100000010001 00000000 192.168.18.0 11000000 1010100000010010 00000000 192.168.19.0 11000000 1010100000010011 00000000 Identify which bits all these networks have in common. 192.168.16.0 /22 can represent all these networks. The router will look at the first 22 bits of the address to make a routing decision. Note that 192.168.16.0 /22 is not a Class C network, it has a subnet mask of 255.255.252.0
Subnet Masks • A major network is a Class A, B, or C network • Fixed-Length Subnet Masking (FLSM) is when all subnet masks in a major network must be the same • Variable-Length Subnet Masking (VLSM) is when subnet masks within a major network can be different. • Some routing protocols require FLSM; others allow VLSM
VLSM • VLSM makes it possible to subnet with different subnet masks and therefore results in more efficient address space allocation. • VLSM also provides a greater capability to perform route summarization, because it allows more hierarchical levels within an addressing plan. • VLSM requires prefix length information to be explicitly sent with each address advertised in a routing update
Subnet Calculator The IP Subnet Mask Calculator enables subnet network calculations using network class, IP address, subnet mask, subnet bits, mask bits, maximum required IP subnets and maximum required hosts per subnet. Results of the subnet calculation provide the hexadecimal IP address, the wildcard mask, for use with ACL (Access Control Lists), subnet ID, broadcast address, the subnet address range for the resulting subnet network and a subnet bitmap. For classless supernetting, please use the CIDR Calculator. For classful supernetting, please use the IP Supernet Calculator. For simple ACL (Access Control List) wildcard mask calculations, please use the ACL Wildcard Mask Calculator. Note:These online network calculators may be used totally free of charge provided their use is from this url (www.subnet-calculator.com).
IP Address with Port Number Notation The : (colon) indicates the number following is a Port Number - in the above case 369. This format is typically only used where a service is available on a non-standard port number, for instance, many web configuration systems, such as Samba swat, will use a non-standard port to avoid clashing with the standard web (HTTP) port number of 80. A port number is 16 bits giving a decimal range of 0 to 65535. In most systems privileged or well-known ports lie in the range 0 - 1023 and require special access rights, normal user ports lie in the range 1024 to 65535. TCP and UDP use protocol port numbers to distinguish among multiple applications that are running on a single device. Example: 192.168.1.2:369
Classful and Classless Routing Protocols • Classful routing protocols DO NOT send subnet mask information in their routing updates • When a router receives a routing update, it simply assumes the default subnet mask (Class A, B, or C) • VLSM cannot be used in networks that use Classfulrouting protocols • Classless routing protocols send the subnet mask (prefix length) in their updates • VLSM can be used with Classless routing protocols
IPv6 Standard • Larger address space: IPv6 addresses are 128 bits, compared to IPv4’s 32 bits. This larger addressing space allows more support for addressing hierarchy levels, a much greater number of addressable nodes, and simpler auto configuration of addresses. • Globally unique IP addresses: Every node can have a unique global IPv6 address, which eliminates the need for NAT. • Site multi-homing: IPv6 allows hosts to have multiple IPv6 addresses and allows networks to have multiple IPv6 prefixes. Consequently, sites can have connections to multiple ISPs without breaking the global routing table. • Header format efficiency: A simplified header with a fixed header size makes processing more efficient.
IPv6 Standard • 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 non default quality of service (QoS) or real-time service.
IPv6 Standard • 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. • Improved global reach ability and flexibility. • Better aggregation of IP prefixes announced in routing tables.
IPv6 Standard • Multi-homed hosts. Multi-homing is a technique to increase the reliability of the Internet connection of an IP network. With IPv6, a host can have multiple IP addresses over one physical upstream link. For example, a host can connect to severalISPs. • Auto-configuration that can include Data Link layer addresses in the address space. • More plug-and-play options for more devices. • Public-to-private, end-to-end readdressing without address translation. This makes peer-to-peer (P2P) networking more functional and easier to deploy. • Simplified mechanisms for address renumbering and modification.
IPv6 Standard • Better routing efficiency for performance and forwarding-rate scalability • No broadcasts and thus no potential threat of broadcast storms • No requirement for processing checksums • Simplified and more efficient extension header mechanisms • Flow labels for per-flow processing with no need to open the transport inner packet to identify the various traffic flows
IPv6 Standard Movement to change from IPv4 to IPv6 has already begun, particularly in Europe, Japan, and the Asia-Pacific region. • These areas are exhausting their allotted IPv4 addresses, which makes IPv6 all the more attractive and necessary. • In 2002, the European Community IPv6 Task Force forged a strategic alliance to foster IPv6 adoption worldwide. • The North American IPv6 Task Force has set out to engage the North American markets to adopt IPv6. • The first significant North American advances are coming from the U.S. Department of Defense (DoD).
IPv6 Standard • Using the "::" notation greatly reduces the size of most addresses as shown. An address parser identifies the number of missing zeros by separating any two parts of an address and entering 0s until the 128 bits are complete
IPv6 Larger address Space IPv4 32 bits or 4 bytes long 4,200,000,000 possible addressable nodes IPv6 128 bits or 16 bytes: four times the bits of IPv4 3.4 * 1038possible addressable nodes 340,282,366,920,938,463,374,607,432,768,211,456 5 * 1028addresses per person
IPv6 Representation x:x:x:x:x:x:x:x,where x is a 16-bit hexadecimal field Leading zeros in a field are optional: 2031:0:130F:0:0:9C0:876A:130B Successive fields of 0 can be represented as ::, but only once per address. Examples: 2031:0000:130F:0000:0000:09C0:876A:130B 2031:0:130f::9c0:876a:130b FF01:0:0:0:0:0:0:1 >>> FF01::1 0:0:0:0:0:0:0:1 >>> ::1 0:0:0:0:0:0:0:0 >>> ::
IPv6 Addressing Model Addresses are assigned to interfaces Change from IPv4 mode: Interface “expected” to have multiple addresses Addresses have scope Link Local Unique Local Global Addresses have lifetime Valid and preferred lifetime
IPv6 Address Types Unicast Address is for a single interface. IPv6 has several types (for example, global and IPv4 mapped). Multicast One-to-many Enables more efficient use of the network Uses a larger address range Anycast One-to-nearest(allocated from unicast address space). Multiple devices share the same address. All anycast nodes should provide uniform service. Source devices send packets to anycast address. Routers decide on closest device to reach that destination. Suitable for load balancing and content delivery services.
IPv6 Global Unicast Addresses • The global unicast and the anycast share the same address format. • Uses a global routing prefix—a structure that enables aggregation upward, eventually to the ISP. • A single interface may be assigned multiple addresses of any type (unicast, anycast, multicast). • Every IPv6-enabled interface must contain at least one loopback (::1/128)and one link-local address. • Optionally, every interface can have multiple unique local and global addresses. • Anycast address is a global unicast address assigned to a set of interfaces (typically on different nodes). • IPv6 anycast is used for a network multihomed to several ISPs that have multiple connections to each other.
IPv6 Transition Strategies • The transition from IPv4 does not require upgrades on all nodes at the same time. Many transition mechanisms enable smooth integration of IPv4 and IPv6. Other mechanisms that allow IPv4 nodes to communicate with IPv6 nodes are available. Different situations demand different strategies. The figure illustrates the richness of available transition strategies. • Recall the advice: "Dual stack where you can, tunnel where you must." These two methods are the most common techniques to transition from IPv4 to IPv6.
IPv6 Transition Strategies Dual stacking is an integration method in which a node has implementation and connectivity to both an IPv4 and IPv6 network. This is the recommended option and involves running IPv4 and IPv6 at the same time. Router and switches are configured to support both protocols, with IPv6 being the preferred protocol.
IPv6 Transition Strategies Tunneling The second major transition technique is tunneling. There are several tunneling techniques available, including: Manual IPv6-over-IPv4 tunneling -An IPv6 packet is encapsulated within the IPv4 protocol. This method requires dual-stack routers. Dynamic 6to4 tunneling -Automatically establishes the connection of IPv6 islands through an IPv4 network, typically the Internet. It dynamically applies a valid, unique IPv6 prefix to each IPv6 island, which enables the fast deployment of IPv6 in a corporate network without address retrieval from the ISPs or registries
Routing Protocols • One of the primary jobs of a router is to determine the best path to a given destination • A router learns paths, or routes, from the static configuration entered by an administrator or dynamically from other routers, through routing protocols
Routing Table Principles Three principles regarding routing tables: • Every router makes its decisions alone, based on the information it has in its routing table. • Different routing table may contain different information • A routing table can tell how to get to a destination but not how to get back (Asymmetric Routing) Routing information about a path from one network to another does not provide routing information about the reverse, or return, path.
Routing Table Structure • PC1 sends ping to PC2 • R1 has a route to PC2’s network • R2 has a route to PC2’s network • R3 is directly connected to PC2’s network • PC2 sends a reply ping to PC1 • R3 has a route to PC1’s network • R2 does not have a route to PC1’s network • R2 drops the ping reply
Routing Tables • Routers keep a routing table in RAM • A routing table is a list of the best known available routes • Routers use this table to make decisions about how to forward a packet • On a Cisco router, the show IP route command is used to view the TCP/IP routing table
Routing Table • A routing table maps network prefixes to an outbound interface. • When RTA receives a packet destined for 192.168.4.46, it looks for the prefix 192.168.4.0/24 in the routing table • RTA then forwards the packet out an interface, such as Ethernet0, as directed in the routing table
Routing Loops • A network problem in which packets continue to be routed in an endless circle • It is caused by a router or line failure, and the notification of the downed link has not yet reached all the other routers • It can also occur over time due to normal growth or when networks are merged together • Routing protocols utilize various techniques to lessen the chance of a routing loop
Routing Table Structure • The primary function of a router is to forward a packet toward its destination network, which is the destination IP address of the packet. • To do this, a router needs to search the routing information stored in its routing table.
Routing Protocols • Routing Table is stored in ram and contains information: • Directly connected networks-this occurs when a device is connected to another router interface • Remotely connected networks-this is a network that is not directly connected to a particular router network/next hop associations-about the networks include source of information, network address & subnet mask, and Ip address of next-hop router • The show ip route command is used to view a routing table on a Cisco router