Week Eight Agenda. Attendance Announcements Review Week Seven Information Current Week Information Upcoming Assignments. Week Eight Topics. Shortage of IP addresses with IPv4 Private, public, and NAT addressing Static or Dynamic IP Address Assignment
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The IPv4 Standard created a problem that was temporarily solved by assigning private addresses within a local network and translating the private addresses to public addresses when Internet connectivity is required.
Are there public, private, or both types of addressing required?
How many end systems will need access to the public network? This includes email, file transfer, or web browsing.
How many end systems require access to visible public network(s). This includes e-commerce, such as web servers, database servers, application servers, and public servers. These end systems require globally unambiguous IP addresses.
Where will the boundaries be between private and public IP addresses and how will they be implemented?
172.16.0.0 –172.31.255.255: 172.16.0.0/12
Where does the /12 come from?
12 bits in common
10101100 . 00010000 . 00000000 . 00000000 –172.16.0.0
10101100 . 00011111 . 11111111 . 11111111 –172.31.255.255
10101100 . 0001000 00000000 . 00000000 –172.16.0.0/12
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
Is a protocol for assigning dynamic IP addresses to devices on a network . With dynamic addressing, a device can have a different IP address every time it connects to the network.
In some systems, the device's IP address can even change while it is still connected. DHCP also supports a mix of static and dynamic IP addresses.
A DHCP Server can provide the following to a client:
DNS server address
Domain Name Server(s)
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
Running Out of IP Addresses There is a maximum number of networks and hosts that can be assigned unique addresses using the Internet's 32-bit long addresses.
Traditionally, the Internet assigned "classes" of addresses: Class A, Class B and Class C were the most common. Each address had two parts: one part to identify a unique network and the second part to identify a unique host in that network.
Another way the old Class A, B, and C addresses were identified was by looking at the first 8 bits of the address and converting it to its decimal equivalent.
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
172.16.0.0 255.255.0.0= 172.16.0.0 /16
184.108.40.206 255.255.255.0= 220.127.116.11 /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 Block Prefix Equivalent Class C of Host Addresses
/24 1 Class C 256 hosts
/23 2 Class C 512 hosts
/22 4 Class C 1,024 hosts
/21 8 Class C 2,048 hosts
/20 16 Class C 4,096 hosts/19 32 Class C 8,192 hosts
/18 64 Class C 16,384 hosts/17 128 Class C 32,768 hosts/16 256 Class C 65,536 hosts
Given four Class C Networks (/24):
192.168.16.0 11000000 10101000 00010000 00000000
192.168.17.0 11000000 10101000 0001000100000000
192.168.18.0 11000000 10101000 0001001000000000
192.168.19.0 11000000 10101000 0001001100000000
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
Importance of Hierarchical Addressing
Without summarization, every small change in the network will be propagated (spread) throughout the entire network
With summarization, small changes in the network aren’t propagated (spread) throughout the entire network
Classful protocols use address classes (A,B,C) to determine networks because subnet masks are not sent in routing updates.
There is static and dynamic (DNS) name resolution.
Root Level Domain
Top Level Domain and Countries
(Australia com edu gov net org )
Second Level Domain
( microsoft franklin cisco )
Movement to change from IPv4 to IPv6 has already begun, particularly in Europe, Japan, and the Asia-Pacific region.
You know the 32-bit IPv4 address as a series of four 8-bit fields, separated by dots. However, larger 128-bit IPv6 addresses need a different representation because of their size. IPv6 addresses use colons to separate entries in a series of 16-bit hexadecimal
Global reach ability and flexibility
End to end without NAT
Performance and forwarding rate scalability
Mobility and security
Mobile IP RFC-compliant
IPSec mandatory(or native) for IPv6
32 bits or 4 bytes long
4,200,000,000 possible addressable nodes
128 bits or 16 bytes: four times the bits of IPv4
3.4 * 1038possible addressable nodes
5 * 1028addresses per person
Aggregation of prefixes announced in the global routing table
Efficient and scalable routing
Improved bandwidth and functionality for user traffic
A simpler and more efficient header means:
64-bit aligned fields and fewer fields
Hardware-based, efficient processing
Improved routing efficiency and performance
faster forwarding rate with better scalability
x:x:x:x:x:x:x:x,where x is a 16-bit hexadecimal field
Leading zeros in a field are optional:
Successive fields of 0 can be represented as ::, but only once per address.
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 >>> ::
Addresses are assigned to interfaces
Change from IPv4 mode:
Interface “expected” to have multiple addresses
Addresses have scope
Addresses have lifetime
Valid and preferred lifetime
Address is for a single interface.
IPv6 has several types (for example, global and IPv4 mapped).
Enables more efficient use of the network
Uses a larger address range
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.
Global unicast and anycast addresses are defined by a global routing prefix, a subnet ID, and an interface ID.
Cisco uses the extended universal identifier (EUI)-64 format to do stateless autoconfiguration.
This format expands the 48-bit MAC address to 64 bits by inserting “FFFE” into the middle 16 bits
IPv6 addressing rules are covered by multiple RFCs.
Architecture defined by RFC 4291.
Unicast: One to one
Link local (FE80::/10)
A single interface may be assigned multiple IPv6 addresses of any type: unicast, anycast, or multicast.
Multicast is frequently used in IPv6 and replaces broadcast
An IPv6 anycast address is a global unicast address that is assigned to more than one interface.
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.
Mandatory address for communication between two IPv6 devices (similar to ARP but at Layer 3)
Automatically assigned by router as soon as IPv6 is enabled
Also used for next-hop calculation in routing protocols
Only link specific scope
Remaining 54 bits could be zero or any manual configured value
Remaining 54 bits
Stage 1: The PC sends a router solicitation to request a prefix for stateless auto configuration
Stage 2: The router replies with a router advertisement.
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.
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