Ccna prep ip subnetting from networkers

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Ccna prep ip subnetting from networkers

  1. 1. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr1© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 1BRKCRT-110214364_04_2008_c1 © 2008 Cisco Systems, Inc. All rights reserved. Cisco PublicBRKCRT-110214364_04_2008_c1© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 2BRKCRT-110214364_04_2008_c1Mastering IPSubnetting ForeverBRKCRT-1102
  2. 2. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr2© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 3BRKCRT-110214364_04_2008_c1AgendaSetting the stageWhy the mastery of IP Subnetting skills is so important in the real worldWhat we know…or think we know, can be a factor in our masteryKey elements in successful execution of the subnetting procedureNo math required, start with the ‘Answer’Use the answer to execute the subnetting procedureImplementing the classful subnetting procedure using theReverse Engineering any IP Addressing schemeThe magic of application in the real worldExtending our IP Subnetting knowledge into Classless schemes—VLSMand CIDRVariable Length Subnet MaskingClassless Inter-Domain Routing (Address Summarization,Supernetting, IP Address Aggregation)1© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 4BRKCRT-110214364_04_2008_c1What You Will Need to Be SuccessfulPen or pencil and multiple sheets of paperAn open mind….If you have failed to master IP subnetting before, it’s ok….If you are already a ‘Master Subnetter Guy’, this session maynot be for you…or you just may learn a shortcut you haven’tused beforeSeek to understand the ‘Keys’ and you will be rewardedwith a skill that will serve you everydayBe willing to practice on your own…if you don’t use it,you WILL lose itFill out your session evaluation
  3. 3. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr3© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 5BRKCRT-110214364_04_2008_c1The Question of the Day…Why are IP Subnetting skills so important in the real world?It is what makes it relevant to you and your situation that makes it important…© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 6BRKCRT-110214364_04_2008_c1Responses—In the Form of QuestionsHow many of you attending today, use IP as the primary protocolin your production network? So it is Relevant?How many of you have ever had to troubleshoot an IP-relatedissue in a network? More Relevance?How many of you currently work in an environment wheresomeone else designed the IP addressing scheme? Still RelevantHow many of you have had a previous opportunity to learn IPSubnetting….and it just didn’t quite stick? Big Aha Relevance!How many of you are already quite successful at mental IPSubnetting? You may want to leave now… I wouldn’t wantto ruin it for you.The key to mastering IP Subnetting forever is to BEGIN with “TheAnswer”…
  4. 4. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr4© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 7BRKCRT-110214364_04_2008_c1Finding the Answer…The answer has always been directly in front of yourface…every time you look at an IP address it is there…You simply may not have recognized itEveryone already has the answer if they deal with IPThe RFCs use mathematics to explain it—RFC 950 and 1123IP networks rely on it to route packets—implemented correctly,of courseYou are here to be able to recognize it, understand it, use it,apply it, reverse it, tweak it and master it…f o r e v e r !…And you cant get ‘it’ onThe answer is based on the IP Address itselfYou have all seen an IP address…so where am I trying to takeyou with all of this?© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 8BRKCRT-110214364_04_2008_c1What We Know Already…or Maybe Not
  5. 5. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr5© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 9BRKCRT-110214364_04_2008_c1What We Know Already…or Maybe Not© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 10BRKCRT-110214364_04_2008_c1What We Know Already…or ShouldAn IP address is 32 bits long—4 separate bytesAn IP Address is represented indotted-decimal notationEach byte represents a decimal number separated by a periodExample: 10.100.30.4 or (010.100.030.004)Each byte has a total of 256 values—0-255The first byte may be the most important to youright now…
  6. 6. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr6© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 11BRKCRT-110214364_04_2008_c1What We Know…or Should (Cont.)There are three (3) usable IP address classes—A, Band CThe first byte identifies the class—“Classification”Correct Classification is the first critical KEY element ofmastering IP subnetting (and finding the Answer)Multicast224.0.0.10D – 224-239DOD ReservedE – 240-2552542,097,152198.23.210. 0C – 192-22365,53416,384150.18. 0 .0B – 128-19116,777,21412724. 0 .0 .0A – 1-127HostsNetworksExampleClass11© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 12BRKCRT-110214364_04_2008_c1Practice: Classification—What Class?1
  7. 7. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr7© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 13BRKCRT-110214364_04_2008_c1Practice: Classification—What Class?1© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 14BRKCRT-110214364_04_2008_c1What We Know…or Should (Cont.)Each IP Address has two parts:Network Number Host NumberThe “Class” identifies the ‘default’ point of separationReferred to as the “Class Boundary” (note the line position)2542,097,152198.23.210. 0C – 192-22365,53416,384150.18. 0 .0B – 128-19116,777,21412724. 0 .0 .0A – 1-127HostsNetworksExampleClass1 2Where you draw the line will ultimately lead you to the…‘Answer’21
  8. 8. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr8© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 15BRKCRT-110214364_04_2008_c1Practice: Class Boundary—Drawthe Line2© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 16BRKCRT-110214364_04_2008_c1Practice: Class Boundary—Drawthe Line2
  9. 9. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr9© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 17BRKCRT-110214364_04_2008_c1How The Line Will Lead Us tothe AnswerIn a Class address, every number to the ‘left’ of the line is staticClass Addresses, left in their classful state, yield exactly ‘1’ subnetEvery number right of the line is ours to use…for what? To make moresubnets, implement services, expand, etc.All bits in the address to the ‘Left” of the line are set to a binary 1This identifies the Network portion of the address and you are leftwith Host portion of the address (set to ‘0s’ by default)The network portion of the address is ‘MASKED’ with ‘1s’122© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 18BRKCRT-110214364_04_2008_c1Subnet Mask—Where We Draw the LineIdentifies the division of the Network and the Hostportion of an IP AddressSubnet masks are used to make routing decisionsAll hosts in a given IP addressing scheme will use the samemask to provide accurate routing—RFC 950The default mask is the number of bits that arereserved by the address class—Default Line positionUsing the default mask will accommodate only one networksubnet in the relative classA custom Subnet Mask can be defined by anAdministrator to accommodate many network subnetsHmmm…Maybe by moving the Line? You guessed it!2
  10. 10. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr10© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 19BRKCRT-110214364_04_2008_c1Using the Default ‘Class’ Mask2121© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 20BRKCRT-110214364_04_2008_c1Using a Custom Subnet Mask21
  11. 11. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr11© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 21BRKCRT-110214364_04_2008_c1Understanding the Custom Subnet MaskClassful Subnetting, Classless (VLSM), CIDR, Supernetting,Summarization, Address Aggregation—you name itThe Customization of the mask is KEYIt Is the key to Mastering the IP Subnetting Process© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 22BRKCRT-110214364_04_2008_c1Before Starting the IPSubnetting ProcessDetermine the ‘type’ of IP addressing to useBecome familiar with reserved addresses (RFC 1918, 2026)Determine your network requirementsNumber of subnets and hosts your implementation requiresIdentify your base address (Class A, B, or C)Get to know the3344
  12. 12. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr12© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 23BRKCRT-110214364_04_2008_c1Determine the ‘Type’ of AddressingScheme to UsePublic Addressing Scheme:Sufficient number of public addresses have been obtained or currently existPrivate Addressing Scheme: Most common (RFC1918)Sufficient number of public addresses cannot obtainedPublic IP Numbers can be obtained only for the Internet-facing hosts (edgerouter, firewall, etc.) from the ISPNAT is used to access public networksYou (or Someone Else) Has Determined the ‘Type’ ofIP Addressing Scheme—Public or Private (RFC 1918)© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 24BRKCRT-110214364_04_2008_c1Reserved Private AddressesRFC 1918 addressesNot routed by Internet routers (filtered by PE Routers)RFC 2026—Link Local Addresses169.254.0.1–169.254.255.255Auto-assigned IP address to local host if DHCP server cannotbe contactedNot routed by any router192.168.255.255192.168.0.0Class C172.31.255.255172.16.0.0Class B10.255.255.25510.0.0.0Class AEnd AddressStart AddressClass
  13. 13. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr13© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 25BRKCRT-110214364_04_2008_c1Other Reserved Addresses127.0.0.1–127.255.255.255Reserved for testing and loopback routines for IP Applicationsping 127.0.0.1—verifies the local host has properly loaded theIP protocol224.0.0.1–224.0.0.255—Class D Multicast (IANA)Reserved for well known services and networktopology mechanisms© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 26BRKCRT-110214364_04_2008_c1Identify Subnetting RequirementsIdentify the maximum number of hosts per subnet :Network saturation and converged service requirementsdetermine maximum hosts in many casesRouter Performance and Growth PotentialIdentify the total number of subnets requiring aunique address:Unique address required for each LAN subnetUniques address required for each WAN subnetIdentify and Create a Subnet Mask that accommodatesthe designThis is where the movement of the Line will come in2233
  14. 14. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr14© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 27BRKCRT-110214364_04_2008_c1Getting to Know the ‘Magic Box’This is the primary tool that makes the process so easyNo Math The box has already done itYou’ll find the ‘Answer’ here every timeThis box represents every possible number in a single IPAddress Byte (Octet) anywhere in the 32-bit IP number1371531631272551248163264128255254252248240224192128Octet 1 Octet 2 Octet 3 Octet 44© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 28BRKCRT-110214364_04_2008_c1How the Magic Box Is Built—Most ImportantBegin with eight (8) placeholders. (Use a block…thiswill make sense later)4
  15. 15. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr15© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 29BRKCRT-110214364_04_2008_c1How the Magic Box Is Built (Cont.)Add the Binary value of each placeholder, right to left1248163264128Then Create the Box around it, leaving room for a topand bottom row4© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 30BRKCRT-110214364_04_2008_c1How the Magic Box Is Built (Cont.)You will now quickly add the numbers across the top, Left to rightCalled adding ‘High-Order Bits’ in the RFC1248163264128The Top row will represent Subnet Mask Values during theSubnetting process0+=128+=192+=224+=240+=248+=252+=254+=2554
  16. 16. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr16© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 31BRKCRT-110214364_04_2008_c1How the Magic Box Is Built (Cont.)You will now quickly add the numbers across the bottom, rightto leftCalled adding ‘Low-Order’ bits in the RFC1248163264128The Numbers in the Bottom row are used to determine the numberof Subnets the IP Scheme allowsAlways add 1 to this number to account for the zero subnet to get an accuratetotal of networks128 192 224 240 248 252 254+2550=1+=3+=7+=15+=31+=63+=127+=2554© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 32BRKCRT-110214364_04_2008_c1The Completed Magic Box!13715316312725512481632641282552542522482402241921284
  17. 17. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr17© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 33BRKCRT-110214364_04_2008_c11371531631272551248163264128255254252248240224192128The Completed Magic Box!41© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 34BRKCRT-110214364_04_2008_c1Subnetting Keys ReviewClassificationA, B or C + Class boundary (default Mask)Line Position defines the Subnet MaskMoved further to the right, more subnets, fewer hosts on eachNetwork Subnetting requirementsNumber of subnets required and Largest subnet of hostsThe Magic BoxProvides all of “The Answers” needed to accomplish thesubnetting tasksWhat then is “The Answer” we have been searching for?“The Magic Number” Defined by the position of the line, (theMask) the magic number is our Network Block Size and theanswer to everything. It is inside of the Magic Box.42315
  18. 18. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr18© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 35BRKCRT-110214364_04_2008_c1Applying the Keys to the ClassfulSubnetting Process (RFC 950)Classify the address!!!Identify the class A-B-CDraw the initial LineFill in the default mask informationObtain information about your networkHow many total subnet are to be included?On a single subnet, what is the maximum number of hosts allowed?Create a custom subnet mask for the entire networkAccomplished by moving the Line to the rightNew Subnet Mask number is left of the Line PositionThe Line Position provides “the Answer”Look in the Magic Box—Find the number directly below the chosen maskvalue—This is the Magic Number …will give you everything you need tocomplete the processSubnet addresses | Range of host IDs | Broadcast addresses425312© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 36BRKCRT-110214364_04_2008_c1Subnetting Example 1:IP Network DesignCentral Office—San Diego23 Ethernet segments—2200 hostsBranch Office—Phoenix12 Ethernet segments—1150 hostsBranch Office—Dallas11 Ethernet segments—950 hostsBranch Office—Denver8 Ethernet segments—850 hosts23 +8 +12 +11 +3 = 57Maximum number of hosts on anyone subnet will be 200
  19. 19. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr19© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 37BRKCRT-110214364_04_2008_c1Subnetting Example 1Base Address:Sample design indicates accommodation of 57 subnets(Including WAN) with no more than 200 hosts persubnet (Including router interfaces)57 is the key factor here. We need to support at least 57subnets312© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 38BRKCRT-110214364_04_2008_c11371531631272551248163264128255254252248240224192128Consult Magic Box! Bottom Row4Octet 3Octet 1 Octet 2
  20. 20. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr20© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 39BRKCRT-110214364_04_2008_c11371531631272551248163264128255254252248240224192128Consult Magic Box! Look at theBottom Row4Octet 3Octet 1 Octet 26© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 40BRKCRT-110214364_04_2008_c11371531631272551248163264128255254252248240224192128Magic Calculation:46Octet 1 Octet 2Octet 3
  21. 21. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr21© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 41BRKCRT-110214364_04_2008_c1137153163127255124816326412825525425224824022419212864What does the New Line PositionTell Us?4Octet 1 Octet 2Octet 364© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 42BRKCRT-110214364_04_2008_c1What We Are Left With for Host IPsRemember the original network design requirements:57 Subnets total—We ended up withMaximum 200 Hosts per Subnet—There are 254 addressavailable in Octet 4 alone (8 bits) and we have 10 bits to useAlways use your host requirement to check your work whenfollowing the classful subnetting procedureOctet 1 Octet 2 Octet 3 Octet 464
  22. 22. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr22© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 43BRKCRT-110214364_04_2008_c1Where We Are in the Process…Classify the address!!!Identify the class A-B-CDraw the initial LineFill in the default mask informationObtain information about your networkHow many total subnet are to be included? 57On a single subnet, what is the maximum number of hosts allowed? 200Create a custom subnet mask for the entire networkAccomplished by moving the Line to the rightNew Subnet Mask number is left of the Line PositionThe Line Position provides “the Answer”Look in the Magic Box – Find the number directly below the chosen mask value—This isthe Magic Number …will give you everything you need to complete the processSubnet addresses | Range of host IDs | Broadcast addresses425312© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 44BRKCRT-110214364_04_2008_c1Completing the Last Step in the ProcessThe “Answer” we have been seeking is ‘4’, defined by the mask orline position, it is the Block Size Increment Value for all subnets,host ranges and broadcast addresses.It will increment times (64 x 4 = 256) in our example1371531631272551248163264128255254252248240224192128645464Octet 3
  23. 23. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr23© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 45BRKCRT-110214364_04_2008_c1Allocating the Subnet, Host and BroadcastAddresses Using , the ‘Magic Number’4Broadcast AddressHost IP RangeSubnet Address© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 46BRKCRT-110214364_04_2008_c1Number of Valid Host IPs Per SubnetTo determine how many hosts can exist per subnet,continue incrementing the binary number from right toleft until you reach 10 bits (1024) and subtract 2Remember that binary continues exponentially, so where wehave 256 values in octet 4 (8 bits) then 512 (9th bit) then 1024(10th bit)Subtract 2—One for the Subnet address and one for theBroadcast Address of each networkOctet 1 Octet 2 Octet 3 Octet 4
  24. 24. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr24© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 47BRKCRT-110214364_04_2008_c1Subnetting Example 1: Applying theSubnets to the Network LocationsCentral Office—San Diego23 Ethernet segments—2200 hostsBranch Office—Dallas11 Ethernet segments—950 hostsBranch Office—Denver8 Ethernet segments—850 hostsBranch Office—Phoenix12 Ethernet segments—1150 hosts172.16.0.0- 88.0172.16.92.0- 136.0172.16.140.0- 180.0172.16.184.0- 212.0172.16.216.0172.16.220.0172.16.224.0© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 48BRKCRT-110214364_04_2008_c1CIDR Notation—Shortcut to theAnswer /nnOctet 1 Octet 2 Octet 3 Octet 4Octet 1 Octet 2 Octet 3 Octet 4
  25. 25. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr25© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 49BRKCRT-110214364_04_2008_c1Magic Box for CIDR Notation and OtherAdvanced IP Subnetting Concepts/32/31/30/29/28/27/26/25/24/23/22/21/20/19/18/17/16/15/14/13/12/11/10/91248163264128255254252248240224192128CIDR Notation in the second octet:CIDR Notation in the third octet:CIDR Notation in the fourth octet:This row is still your Subnet MaskValue:© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 50BRKCRT-110214364_04_2008_c1Reverse Engineering Any IP SchemeGiven an IP address and mask, what is the subnet address?Given an IP address and mask, what is the subnetbroadcast address?Given an IP address and mask, what are the assignable IPaddresses in that network/subnet?Given a network number and a static subnet mask, what arethe valid subnet numbers?Here is all of the information you may be have:One of the Most Powerful Troubleshooting SkillsYou Can Keep in Your Arsenal
  26. 26. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr26© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 51BRKCRT-110214364_04_2008_c1The ‘Answer’ has already been given to you:Second octet will not change since the mask is in the third at /21To Reverse Engineer, simply start incrementing by 8 until youcome to the range the specified host lives in:0, 8, 16, 24, 32, 40. (done)Reverse Engineering by Usingthe ‘Answer’Octet 1 Octet 2 Octet 3 Octet 4© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 52BRKCRT-110214364_04_2008_c1Reverse Engineering Results1. Given an IP address and mask, what is thesubnet number?2. Given an IP address and mask, what is the subnetbroadcast address?3. Given an IP address and mask, what are theassignable IP addresses in that network/subnet?4. Given a network number and a static subnet mask,what are the valid subnet numbers?
  27. 27. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr27© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 53BRKCRT-110214364_04_2008_c1Great Job! You Have Passed Level 1!You have just learned the entire classful subnettingprocess using no mathEverything else from here on out, uses these exact techniques,tools and processesLevel 2—Classless Subnetting (VLSM)Level 3 —Classless Inter-Domain Routing (CIDR)Supernetting, Address Aggregation, Summary Addressing© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 54BRKCRT-110214364_04_2008_c1Variable Length SubnetMasking—VLSM(RFC 1818)
  28. 28. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr28© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 55BRKCRT-110214364_04_2008_c1Subnetting (Classless) VLSMAllows for more efficient use of IP spaceLess waste on smaller subnets where fewer addressesare necessaryUsed frequently if public address are used internally orunplanned growth needs to be accommodated inside ofa siteDefined first in RFP 1009 then ratified as the latestRFC 1878Variable Length Subnet Masking© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 56BRKCRT-110214364_04_2008_c1Understanding VLSMInstead of creating a single subnet mask toaccommodate your total IP Subnet number(working from the left)Identify a subnet mask for each subnet individually(work from the right side)Move the line as far to the right as you can, while leaving justenough room for the Hosts on that subnetUse the bottom row of the Magic Box to complete this taskUse the Magic Box separately for each physical subnet
  29. 29. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr29© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 57BRKCRT-110214364_04_2008_c1VLSM Problem 11371531631272551248163264128255254252248240224192128Using network 172.16.0.0Create a Mask for a subnet containing 90 hosts127 is bigger than 9063 is not128 will be the Maskin the 4th octetSubnet Mask for this Problem is (solution) 255.255.255.128 /25 maskOctet 4© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 58BRKCRT-110214364_04_2008_c11371531631272551248163264128255254252248240224192128VLSM Problem 2Octet 4Using network 10.0.0.0Create a Mask for a subnet containing 2 hosts3 is bigger than 21 is not252 will be the Maskin the 4th octetSubnet Mask for this Problem is (solution) 255.255.255.252 /30 mask
  30. 30. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr30© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 59BRKCRT-110214364_04_2008_c11371531631272551248163264128255254252248240224192128VLSM Problem 3Octet 4Using network 10.0.0.0Create a Mask for a subnet containing 20 hosts31 is bigger than 2015 is not224 will be the Maskin the 4th octetSubnet Mask for this Problem is (solution) 255.255.255.224 /27 mask© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 60BRKCRT-110214364_04_2008_c11371531631272551248163264128255254252248240224192128Octet 3VLSM Problem 4Octet 45111023256512255254Using network 10.0.0.0Create a Mask for a subnet containing 300 hosts511 is bigger than 300255 is notSubnet Mask for this Problem is (solution) 255.255.254.0 /23 mask254 will be the Maskin the 3rd octetStart by extending theMagic Box
  31. 31. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr31© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 61BRKCRT-110214364_04_2008_c1Applying VLSM to a Network DesignIdentify all of the subnets within your operational areaand determine their approximate size (Host Population)VLSM must be implemented on a standard BinaryBlock Size: 2, 4, 8,16, 32, and so onAll Routers and Multi-Layer Switches must be running arouting protocol capable of exchanging Subnet Maskinformation within their route update packetsClassless Routing protocols, like EIGRP, OSPF and RIP2When Implementing VLSM, allocate Subnet IDs to thelargest networks first, then work your way down to thesmallest networksRules:© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 62BRKCRT-110214364_04_2008_c1Subnetting Example 2: VLSM DesignBranch Office—Dallas11 Ethernet segments—950 hosts172.16.0.0- 88.0172.16.92.0- 136.0172.16.140.0- 180.0172.16.184.0- 212.0172.16.216.0172.16.220.0172.16.224.0Central Office—San Diego23 Ethernet segments—2200 hostsBranch Office—Phoenix12 Ethernet segments—1150 hostsBranch Office—Denver8 Ethernet segments—850 hosts
  32. 32. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr32© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 63BRKCRT-110214364_04_2008_c1Subnetting Example 2: VLSM DesignBranch Office—Dallas28 Ethernet segments—1950 hosts172.16.0.0- 88.0172.16.92.0- 136.0172.16.140.0- 180.0172.16.184.0- 212.0172.16.216.0172.16.220.0172.16.224.0Central Office—San Diego23 Ethernet segments—2200 hostsBranch Office—Phoenix12 Ethernet segments—1150 hostsBranch Office—Denver8 Ethernet segments—850 hosts© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 64BRKCRT-110214364_04_2008_c1Subnetting Example 2: VLSM Design172.16.140.0- 180.0 /22Branch Office—Dallas28 Ethernet segments—1950 hosts
  33. 33. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr33© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 65BRKCRT-110214364_04_2008_c1Subnetting Example 2: VLSMDesign (Cont.)172.16.140.0- 180.0 /22Branch Office—Dallas28 Ethernet segments—1950 hosts© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 66BRKCRT-110214364_04_2008_c11371531631272551248163264128255254252248240224192128So How Do We Do It?EASY…Octet 4
  34. 34. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr34© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 67BRKCRT-110214364_04_2008_c11371531631272551248163264128255254252248240224192128Computing the Mask for theLarge Subnets~114 network device IP addresses requiredOctet 4127 is bigger than 114,63 is not1371531631272551248163264128255254252248240224192128© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 68BRKCRT-110214364_04_2008_c113715316312725512481632641282552542522482402241921281371531631272551248163264128255254252248240224192128Computing the Mask for theSmall Subnets60 network device IP addresses requiredOctet 463 is bigger than 60,31 is not
  35. 35. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr35© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 69BRKCRT-110214364_04_2008_c1Address Allocation for DallasStart with the Large Subnets (128 block)Beginning with 172.16.140.0 as base address172.16.141.255172.16.141.129 - .141.254172.16.141.128172.16.141.127172.16.141.1 – .140.126172.16.141.0172.16.140.255172.16.140.129 – .140.254172.16.140.128172.16.140.127172.16.140.1 – .140.126172.16.140.0Broadcast AddressHost RangeSubnet ID2134© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 70BRKCRT-110214364_04_2008_c1Address Allocation for Dallas (Cont.)Now create the ranges for the small subnets (64 block)Beginning with 172.16.142.0 as base address (where we left off)172.16.147.255172.16.147.193 – .147.254172.16.147.192…and you end up with……12 more subnets are built……and so on…172.16.143.255172.16.143.193 – .143.254172.16.143.192172.16.143.191172.16.143.129 – .143.190172.16.143.128172.16.143.127172.16.143.65 – .143.126172.16.143.64172.16.143.63172.16.143.1 – .143.62172.16.143.0172.16.142.255172.16.142.193 – .142.254172.16.142.192172.16.142.191172.16.142.129 – .142.190172.16.142.128172.16.142.127172.16.142.65 – .142.126172.16.142.64172.16.142.63172.16.142.1 – .142.62172.16.142.0Broadcast AddressHost RangeSubnet ID56789101112…24
  36. 36. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr36© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 71BRKCRT-110214364_04_2008_c1Level 3—RFCs 1338 and 1519Same Game…Many NamesCIDR—Classless Inter-Domain RoutingSupernettingIPv4 Address AggregationIP Address SummarizationAll of these follow the same basic processAdvertise a single IP Subnet Address/Mask on a router whichimplies multiple IP Subnets10.0.0.0/8 implies all ’10’ networksMust have a contiguous ‘block’ to implement ( 2, 4, 8, 16,32, etc)© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 72BRKCRT-110214364_04_2008_c1Classless Interdomain RoutingOne method to help control IP addresses depletionReduce Internet routing table size (BGP Table)Blocks of Contiguous Addresses (4, 8,16, etc) are assignedto ISPsISPs assign IP addresses to Customers in contiguous blocksBlocks are summarized to reduce router advertisements androute table sizeCheck outwww.traceroute.org/#USA Scroll down to Route Servers whereyou can telnet to a live Cisco BGP router and view the completeBGP Table
  37. 37. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr37© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 73BRKCRT-110214364_04_2008_c1What Is CIDR?Customer Edge NetworkRequires 4 Class C Addresses210.40.8.0/24210.40.9.0/24210.40.10.0/24210.40.11.0/24Internet Service Provider210.40.8.0/22Global InternetPECE© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 74BRKCRT-110214364_04_2008_c1Supernetting, Summarization,Aggregation Example192.168.103.0/24192.168.102.0/24192.168.101.0/24192.168.100.0/24192.168.99.0/24192.168.98.0/24192.168.97.0/24192.168.96.0/24168168168168168168168168........0.01100111.192=0.01100110.192=0.01100101.192=0.01100100.192=0.01100011.192=0.01100010.192=0.01100001.192=0.01100000.192=CommonCommonBitsBitsThere are 21 bits which all of the networks have in commonThere are 21 bits which all of the networks have in commonTherefore, the best summary address would be:Therefore, the best summary address would be:Actual Network Addresses
  38. 38. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr38© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 75BRKCRT-110214364_04_2008_c1Supernetting, Summarization,Aggregation Example (Cont.)Octet 1 Octet 2 Octet 3 Octet 4© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 76BRKCRT-110214364_04_2008_c1Q and A
  39. 39. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr39© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 77BRKCRT-110214364_04_2008_c1Recommended ReadingContinue your Networkers atCisco Live learningexperience with furtherreading from Cisco PressCheck the RecommendedReading flyer for suggestedbooksAvailable Onsite at the Cisco Company Store© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 78BRKCRT-110214364_04_2008_c1Complete Your OnlineSession EvaluationGive us your feedback and you could winfabulous prizes. Winners announced daily.Receive 20 Passport points for each sessionevaluation you complete.Complete your session evaluation online now(open a browser through our wireless networkto access our portal) or visit one of the Internetstations throughout the Convention Center.Don’t forget to activateyour Cisco Live virtualaccount for access toall session materialon-demand and returnfor our live virtual eventin October 2008.Go to the CollaborationZone in World ofSolutions or visitwww.cisco-live.com.
  40. 40. © 2006, Cisco Systems, Inc. All rights reserved.Presentation_ID.scr40© 2008 Cisco Systems, Inc. All rights reserved. Cisco Public 79BRKCRT-110214364_04_2008_c1

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