THE INTERNET PROTOCOL AND OTHER NETWORK ADDRESSING SYSTEMS RECOGNIZE THREE MAIN ADDRESSING METHODOLOGIES ARE ;
IN IPv4 THREE TYPES OF PACKETS CAN EXIST ON AN IPv4 NETWORK :
1. UNICAST – A Packet Sent From One Host To Only One Other Host. A Hub Will Forward A Unicast Out All Ports. If A Switch Has A Table Entry For The Unicast’s MAC Address, It Will Forward It Out Only The Appropriate Port.
UNICAST ADDRESSING - Uses A One-To-One Association Between Destination Address And Network Endpoint: Each Destination Address Uniquely Identifies A Single Receiver Endpoint.
Note : An Unicast Address Corresponds To A Single Interface On A Single Host, While A Multicast Address Can Correspond To Multiple Hosts.
A Unicast Address Is An Address That Identifies A Unique Node On A Network. Unicast Addressing Is Available In Ipv4 And Ipv6 And Typically Refers To A Single Sender Or A Single Receiver, Although It Can Be Used In Both Sending And Receiving.
A Unicast Address Packet Is Transferred To A Network Node, Which Includes An Interface Address. The Unicast Address Is Then Inserted Into The Destination's Packet Header, Which Is Sent To The Network Device Destination.
A Unicast Address Identifies A Network Device, Such As A Workstation Or A Server. A Unicast Address On A Local Area Network (LAN) Contains A Subnet Prefix And An Interface ID.
BROADCAST OR MULTICAST - Addressing Uses A One-To-Many Association, Datagrams Are Routed From A Single Sender To Multiple Endpoints Simultaneously In A Single Transmission. The Network Automatically Replicates Datagrams As Needed For All Network Segments (Links) That Contain An Eligible Receiver.
2. BROADCAST – A Packet Sent From One Host To All Hosts On The IP Subnet. Both Hubs And Switches Will Forward A Broadcast Out All Ports. By Definition, A Router Will Not Forward A Broadcast From One Segment To Another.
3. MULTICAST – A Packet Sent From One Host To A Specific Group Of Hosts. Switches, By Default, Will Forward A Multicast Out All Ports. A Router, Bydefault, Will Not Forward A Multicast From One Segment To Another.
IPv4 MULTICAST ADDRESSING:
Ipv4 Addresses Are Separated Into Several “Classes.”
Class A: 1.1.1.1 – 127.255.255.255
Class B: 128.0.0.0 – 191.255.255.255
Class C: 192.0.0.0 – 223.255.255.255
Class D: 224.0.0.0 – 239.255.255.255
IP CLASS D ADDRESSES :
IP Multicast Addresses Have Been Assigned To The Ipv4 Class D Address Space By IANA. The High-Order Four Bits Of A Class D Address Are 1110. Therefore, Host Group Addresses Can Be In The Range 224.0.0.0 To 239.255.255.255. A Multicast Address Is Chosen At The Source (Sender) For The Receivers In A Multicast Group.
Class D Addresses Have Been Reserved For Multicast. Within The Class D Address Space, Several Ranges Have Been Reserved For Specific Purposes:
IPV6 ADDRESSING :
Ipv6 Has Three Main Types Of Addresses. Unicast And Multicast Addresses Are Similar To Their Ipv4 Companions. A New Type Of Address, Anycast, Has Also Been Introduced In Ipv6.
THE FOLLOWING DESCRIBE THESE IPV6 ADDRESS TYPES:
There Are No Broadcast Addresses In Ipv6, Their Function Being Superseded By Multicast Addresses.
ADDRESSING MODEL
Ipv6 Addresses Of All Types Are Assigned To Interfaces, Not Nodes. An Ipv6 Unicast Address Refers To A Single Interface. Since Each Interface Belongs To A Single Node, Any Of That Node's Interfaces' Unicast Addresses May Be Used As An Identifier For The Node.
All Interfaces Are Required To Have At Least One Link-Local Unicast Address A Single Interface May Also Have Multiple Ipv6 Addresses Of Any Type (Unicast, Anycast, And Multicast) Or Scope.
Unicast Addresses With Scope Greater Than Link-Scope Are Not Needed For Interfaces That Are Not Used As The Origin Or Destination Of Any Ipv6 Packets To Or From Non-Neighbors. This Is Sometimes Convenient For Point-To-Point Interfaces.
THERE IS ONE EXCEPTION TO THIS ADDRESSING MODEL :
A Unicast Address Or A Set Of Unicast Addresses May Be Assigned To Multiple Physical Interfaces If The Implementation Treats The Multiple Physical Interfaces As One Interface When Presenting It To The Internet Layer. This Is Useful For Load-Sharing Over Multiple Physical Interfaces.
Currently Ipv6 Continues The Ipv4 Model That A Subnet Prefix Is Associated With One Link. Multiple Subnet Prefixes May Be Assigned To The Same Link.
THERE ARE THREE CONVENTIONAL FORMS FOR REPRESENTING IPV6 ADDRESSES AS TEXT STRINGS :
Examples:
FEDC:BA98:7654:3210:FEDC:BA98:7654:3210
1080:0:0:0:8:800:200C:417A
Note That It Is Not Necessary To Write The Leading Zeros In An Individual Field, But There Must Be At Least One Numeral In Every Field (Except For The Case Described In 2.).
The Use Of "::" Indicates One Or More Groups Of 16 Bits Of Zeros. The "::" Can Only Appear Once In An Address. The "::" Can Also Be Used To Compress Leading Or Trailing Zeros In An Address.
FOR EXAMPLE, THE FOLLOWING ADDRESSES:
1080:0:0:0:8:800:200C:417A - > A Unicast Address
FF01:0:0:0:0:0:0:101 - > A Multicast Address
0:0:0:0:0:0:0:1 - > The Loopback Address
0:0:0:0:0:0:0:0 - > The Unspecified Addresses
MAY BE REPRESENTED AS:
1080::8:800:200C:417A - >A Unicast Address
FF01::101 - >A Multicast Address
::1 - > The Loopback Address
:: - > The Unspecified Addresses
0:0:0:0:0:0:13.1.68.3
0:0:0:0:0:FFFF:129.144.52.38
Or In Compressed Form:
::13.1.68.3
:: FFFF:129.144.52.38
THE UNSPECIFIED ADDRESS :
The Address 0:0:0:0:0:0:0:0 Is Called The Unspecified Address. It Must Never Be Assigned To Any Node. It Indicates The Absence Of An Address. One Example Of Its Use Is In The Source Address Field Of Any Ipv6 Packets Sent By An Initializing Host Before It Has Learned Its Own Address.
The Unspecified Address Must Not Be Used As The Destination Address Of Ipv6 Packets Or In Ipv6 Routing Headers. An Ipv6 Packet With A Source Address Of Unspecified Must Never Be Forwarded By An Ipv6 Router.
THE LOOPBACK ADDRESS :
The Unicast Address 0:0:0:0:0:0:0:1 Is Called The Loopback Address. It May Be Used By A Node To Send An Ipv6 Packet To Itself. It May Never Be Assigned To Any Physical Interface. It Is Treated As Having Link-Local Scope, And May Be Thought Of As The Link-Local Unicast Address Of A Virtual Interface (Typically Called "The Loopback Interface") To An Imaginary Link That Goes Nowhere.
The Loopback Address Must Not Be Used As The Source Address In Ipv6 Packets That Are Sent Outside Of A Single Node. An Ipv6 Packet With A Destination Address Of Loopback Must Never Be Sent Outside Of A Single Node And Must Never Be Forwarded By An Ipv6 Router. A Packet Received On An Interface With Destination Address Of Loopback Must Be Dropped.
Ipv6 Unicast Addresses Are Aggregable With Prefixes Of Arbitrary Bit-Length Similar To Ipv4 Addresses Under Classless Interdomain Routing.
There Are Several Types Of Unicast Addresses In Ipv6, In Particular Global Unicast, Site-Local Unicast, And Link-Local Unicast. There Are Also Some Special-Purpose Subtypes Of Global Unicast, Such As Ipv6 Addresses With Embedded Ipv4 Addresses Or Encoded Nsap Addresses. Additional Address Types Or Subtypes Can Be Defined In The Future.
A IPv6 UNICAST ADDRESS IDENTIFIES A SINGLE INTERFACE WITHIN THE SCOPE OF THE UNICAST ADDRESS TYPE:
With The Appropriate Unicast Routing Topology, Packets Addressed To A Unicast Address Are Delivered To A Single Interface.
AGGREGATABLE GLOBAL UNICAST ADDRESSES
AGGREGATABLE GLOBAL UNICAST ADDRESSES, Also Known As Global Addresses, Are Identified By The Format Prefix Of 001. Addresses Of This Type Are Designed To Be Aggregated Or Summarized To Produce An Efficient Routing Infrastructure. They Are Equivalent To Public Ipv4 Addresses. Unlike The Current Ipv4-Based Internet, Which Has A Mixture Of Both Flat And Hierarchical Routing, The Ipv6-Based Internet Has Been Designed From Its Foundation To Support Efficient, Hierarchical Addressing And Routing.
AGGREGATABLE GLOBAL UNICAST ADDRESSES Are Globally Routable And Reachable On The IPv6 Portion Of The Internet. The Region Of The Internet Over Which The Aggregatable Global Unicast Address Is Unique (The Scope) Is The Entire Ipv6 Internet.
LOCAL-USE IPV6 UNICAST ADDRESSES :
There Are Two Types Of Local-Use Unicast Addresses Defined. These Are Link-Local And Site-Local. The Link-Local Is For Use On A Single Link And The Site-Local Is For Use In A Single Site.
LINK-LOCAL ADDRESSES
LOCAL ADDRESSES Are Used By Nodes When Communicating With Neighboring Nodes On The Same Link. For Example, On A Single Link Ipv6 Network With No Router, Link-Local Addresses Are Used To Communicate Between Hosts On The Link. Link-Local Addresses Are Equivalent To Automatic Private Ip Addressing (Apipa) Ipv4 Addresses Using The 169.254.0.0/16 Prefix.
The Scope Of A Link-Local Address Is The Local Link. An Ipv6 Router Never Forwards Link-Local Traffic Beyond The Link. A Link-Local Address Is Required For Neighbor Discovery Processes And Is Always Automatically Configured, Even In The Absence Of All Other Unicast Addresses.
LINK-LOCAL ADDRESSES Are Identified By The Format Prefix Of 1111 1110 10. The Address Always Begins With Fe80. With The 64-Bit Interface Identifier, The Prefix For Link-Local Addresses Is Always Fe80::/64.
LINK-LOCAL ADDRESSES ARE DESIGNED To Be Used For Addressing On A Single Link For Purposes Such As Automatic Address Configuration, Neighbor Discovery, Or When No Routers Are Present.
Routers Must Not Forward Any Packets With Link-Local Source Or Destination Addresses To Other Links.
SITE-LOCAL ADDRESSES Are Designed To Be Used For Addressing Inside Of A Site Without The Need For A Global Prefix. Although A Subnet ID May Be Up To 54-Bits Long, It Is Expected That Globally-Connected Sites Will Use The Same Subnet Ids For Site-Local And Global Prefixes.
Routers Must Not Forward Any Packets With Site-Local Source Or Destination Addresses Outside Of The Site.
ANYCAST ADDRESSES :
ANYCAST ADDRESSING - Routes Datagrams To A Single Member Of A Group Of Potential Receivers That Are All Identified By The Same Destination Address. This Is A One-To-One-Of-Many Association.
AN ANYCAST ADDRESS IDENTIFIES MULTIPLE INTERFACES, And Is Used For One-To-One-Of-Many Communication, With Delivery To A Single Interface. With The Appropriate Routing Topology, Packets Addressed To An Anycast Address Are Delivered To A Single Interface. In Terms Of Routing Distance, A Packet Addressed To An Anycast Address Is Delivered To The Nearest Interface Identified By The Address.
To Facilitate Delivery To The Nearest Anycast Group Member, The Routing Infrastructure Must Be Aware Of The Interfaces That Are Assigned Anycast Addresses And Must Know Their Distances In Terms Of Routing Metrics. At Present, Anycast Addresses Are Used Only As Destination Addresses And Are Assigned Only To Routers.
Anycast Addresses Are Assigned From The Unicast Address Space. The Scope Of An Anycast Address Is The Scope Of The Unicast Address Type From Which The Anycast Address Is Assigned.
The Subnet-Router Anycast Address Is Predefined And Is Required. It Is Used For Communication With One Of Multiple Routers Attached To A Remote Subnet, And Is Created From The Subnet Prefix For A Given Interface.
To Construct The Subnet-Router Anycast Address, The Bits In The Subnet Prefix Are Fixed At Their Appropriate Values And The Remaining Bits Are Set To 0. All Router Interfaces Attached To A Subnet Are Assigned The Subnet-Router Anycast Address For That Subnet.
An Ipv6 Anycast Address Is An Address That Is Assigned To More Than One Interface (Typically Belonging To Different Nodes), With The Property That A Packet Sent To An Anycast Address Is Routed To The "Nearest" Interface Having That Address, According To The Routing Protocols' Measure Of Distance.
Anycast Addresses Are Allocated From The Unicast Address Space, Using Any Of The Defined Unicast Address Formats. Thus, Anycast Addresses Are Syntactically Indistinguishable From Unicast Addresses. When A Unicast Address Is Assigned To More Than One Interface, Thus Turning It Into An Anycast Address, The Nodes To Which The Address Is Assigned Must Be Explicitly Configured To Know That It Is An Anycast Address.
For Any Assigned Anycast Address, There Is A Longest Prefix P Of That Address That Identifies The Topological Region In Which All Interfaces Belonging To That Anycast Address Reside. Within The Region Identified By P, The Anycast Address Must Be Maintained As ASeparate Entry In The Routing System (Commonly Referred To As A "Host Route"); Outside The Region Identified By P, The Anycast Address May Be Aggregated Into The Routing Entry For Prefix P.
Note That In The Worst Case, The Prefix P Of An Anycast Set May Be The Null Prefix, I.E., The Members Of The Set May Have No Topological Locality. In That Case, The Anycast Address Must Be Maintained As A Separate Routing Entry Throughout The Entire Internet, Which Presents A Severe Scaling Limit On How Many Such "Global" Anycast Sets May Be Supported. Therefore, It Is Expected That Support For Global Anycast Sets May Be Unavailable Or Very Restricted.
One Expected Use Of Anycast Addresses Is To Identify The Set Of Routers Belonging To An Organization Providing Internet Service. Such Addresses Could Be Used As Intermediate Addresses In An Ipv6 Routing Header, To Cause A Packet To Be Delivered Via A Particular Service Provider Or Sequence Of Service Providers.
Some Other Possible Uses Are To Identify The Set Of Routers Attached To A Particular Subnet, Or The Set Of Routers Providing Entry Into A Particular Routing Domain.
IMPORTEND ON IPv6 ANYCAST ADDRESSES :
MULTICAST ADDRESSES :
An Ipv6 Multicast Address Is An Identifier For A Group Of Interfaces Typically On Different Nodes). An Interface May Belong To Any Number Of Multicast Groups.
A Multicast Address Identifies Multiple Interfaces, And Is Used For One-To-Many Communication. With The Appropriate Multicast Routing Topology, Packets Addressed To A Multicast Address Are Delivered To All Interfaces That Are Identified By The Address.
Ipv6 Multicast Addresses Have The Format Prefix Of 1111 1111. An Ipv6 Address Is Simple To Classify As Multicast Because It Always Begins With FF. Multicast Addresses Cannot Be Used As Source Addresses.
Multicast Addresses Include Additional Structure To Identify Their Flags, Scope, And Multicast Group. As Shown In The Following Illustration.
CONCLUSION:
The Goal Of This Article Is To Give An Easy Way To Understand The Addressing Methodologies (IPv4 & IPv6) . Hope This Article Will Help Every Beginners Who Are Going To Start Cisco Lab Practice Without Any Doubts. Thank You And Best Of Luck.
This Article Written Author By: Premakumar Thevathasan. CCNA, CCNP, CCIP, MCSE, MCSA, MCSA - MSG, CIW Security Analyst, CompTIA Certified A+.
DISCLAIMER:
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