Mastering IP Subnetting Forever - UCF Department of EECS

1 Mastering IP Subnetting Forever BRKCRT-9346 Scott Morris & Keith Barker 2 2013 Cisco and/or its affiliates. All rights reserved. BRKCRT-9346 Cisco Public Tour Guide Scott Morris, CCIEx4 #4713, CCDE #2009::13, JNCIEx2 CCIE Route & Switch, ISP/Dial, Security, Service Provider Cisco Certified Design Expert Juniper Networks JNCIE-M #153 and JNCIE-ER #102 CISSP, CCVP and several other random things! Email: Twitting: @ScottMorrisCCIE 3 2013 Cisco and/or its affiliates. All rights reserved. BRKCRT-9346 Cisco Public Tour Guide Keith Barker, CCIEx2 #6783, CCDP, CCSI CCIE Route & Switch, Security HP-MASE, Brocade BCNP Juniper Networks JNCIS-ENT/SP Twitter: @KeithBarkerCCIE YouTube: Keith6783 4 2013 Cisco and/or its affiliates.

2 All rights reserved. BRKCRT-9346 Cisco Public Journey Understanding an IPv4 Address Mastering the Mask Custom Subnetting VLSM and Beyond 5 2013 Cisco and/or its affiliates. All rights reserved. BRKCRT-9346 Cisco Public Setting the stage Why the mastery of IP Subnetting skills is so important in the real world What we think we know, can be a factor in our mastery Key elements in successful execution of the Subnetting procedure Creating a MB-Key, identifying the need in the network, and using your thumbs (and other digits) to create a Subnetting addressing scheme Reverse Engineering any IP addressing scheme The magic of application in the real world Extending our IP Subnetting knowledge into Classless schemes VLSM and CIDR Variable Length Subnet Masking Classless Inter-Domain Routing (Address Summarization, Supernetting, IP Address Aggregation)

3 IPv4 Agenda 6 2013 Cisco and/or its affiliates. All rights reserved. BRKCRT-9346 Cisco Public Something to write with, and write on An open If you have failed to master IP Subnetting before, it s If you are already a Jedi Master Subnetter , this session may not be for or you just may learn a shortcut you haven t used before Be willing to practice on your if you don t use it, you WILL lose it Fill out your session evaluation What You Will Need To Be Successful 7 8 2013 Cisco and/or its affiliates. All rights reserved. BRKCRT-9346 Cisco Public Let s play everyone s favorite game Guess that network! 9 2013 Cisco and/or its affiliates. All rights reserved.

4 BRKCRT-9346 Cisco Public What We Know or Maybe Not 10 2013 Cisco and/or its affiliates. All rights reserved. BRKCRT-9346 Cisco Public What We Know or Maybe Not 11 2013 Cisco and/or its affiliates. All rights reserved. BRKCRT-9346 Cisco Public An IPv4 address is 32 bits long 4 separate bytes An IP address is represented in dotted-decimal notation Each byte is represented by a decimal number separated by a period (called dotted decimal notation) Example: or ( ) Each byte represented as decimal number (0 255) The first byte may be the most important to you when you What We Know or Should 12 2013 Cisco and/or its affiliates. All rights reserved. BRKCRT-9346 Cisco Public There are three (3) usable unicast IP address classes - A, B and C The first byte/number/octet identifies the class that the IP belongs to Classification Correct Classification is a starting point, for Mastering IP Subnetting What We or Should (Cont.)

5 Class Example # of Networks # of Hosts on each network A 1-127 24. 0 .0 .0 127 16,777,214 B 128-191 0 .0 16,384 65,534 C 192-223 0 2,097,152 254 D 224-239 Multicast E 240-255 Reserved 13 2013 Cisco and/or its affiliates. All rights reserved. BRKCRT-9346 Cisco Public Let s Name that class! 14 2013 Cisco and/or its affiliates. All rights reserved. BRKCRT-9346 Cisco Public Practice: Classification What Class does each IP below belong to? 15 2013 Cisco and/or its affiliates. All rights reserved. BRKCRT-9346 Cisco Public Practice: Classification What Class? 16 17 2013 Cisco and/or its affiliates. All rights reserved. BRKCRT-9346 Cisco Public Each IP address has two parts: Network Number Host Number Each class uses a different default mask, as a default point of separation between Network and Host Referred to as the Class Boundary (note the line position) Why Knowing the Class Matters Class Example Networks Hosts A 1-127 24.

6 0 .0 .0 127 16,777,214 B 128-191 0 .0 16,384 65,534 C 192-223 0 2,097,152 254 1 2 18 2013 Cisco and/or its affiliates. All rights reserved. BRKCRT-9346 Cisco Public Please put your thinking caps on, it is time for a quiz. One, two, 19 2013 Cisco and/or its affiliates. All rights reserved. BRKCRT-9346 Cisco Public Practice: Class Boundary Draw the default Line 20 2013 Cisco and/or its affiliates. All rights reserved. BRKCRT-9346 Cisco Public Practice: Class Boundary Draw the Line (Cont.) 21 2013 Cisco and/or its affiliates. All rights reserved. BRKCRT-9346 Cisco Public In a classful address, every number to the left of the line is static, and represents the street or network name.

7 Classful addresses, left in their classful state, yield exactly 1 subnet (or street) Every number right of the line is ours to what? Host addresses and/or creating custom subnets All bits in the mask to the left of the line are set to a binary 1 (which indicates those bits are network bits) This identifies the Network portion of the address. The network portion of the address is MASKED with 1s How the Line Is Defined 22 2013 Cisco and/or its affiliates. All rights reserved. BRKCRT-9346 Cisco Public 0000 1010. 0000 0001 . 0000 0000 . 1100 1000 1111 1111. 0000 0000 . 0000 0000 . 0000 0000 Network | Host bits . Host bits . Host bits 23 2013 Cisco and/or its affiliates.

8 All rights reserved. BRKCRT-9346 Cisco Public Identifies the division between the Network and the Host portion of an IP Address All devices on common network share the same mask, and network bits (same street name). The default mask is the number of bits that are reserved by the address class Default Line position Using the default mask will accommodate only one network (no custom subnets) in the relative class A custom Subnet Mask can be defined by an administrator to accommodate new subnetworks. Done by moving the the dividing line to the right. Subnet Mask Where We Draw the Line 24 2013 Cisco and/or its affiliates. All rights reserved. BRKCRT-9346 Cisco Public Using the Default Class Mask 1 2 1 25 2013 Cisco and/or its affiliates.

9 All rights reserved. BRKCRT-9346 Cisco Public Using a Custom Subnet Mask 2 1 26 2013 Cisco and/or its affiliates. All rights reserved. BRKCRT-9346 Cisco Public Why are IPv4 Subnetting skills so important in the real world? It is what makes it relevant to you and your situation that makes it The Question of the 27 2013 Cisco and/or its affiliates. All rights reserved. BRKCRT-9346 Cisco Public It is the key to Mastering the IP Subnetting process Classful Subnetting , classless (VLSM), CIDR, supernetting, summarization, address aggregation you name it the customization of the mask is KEY Understanding the Custom Subnet Mask 28 2013 Cisco and/or its affiliates.

10 All rights reserved. BRKCRT-9346 Cisco Public Determine the type of IP addressing to use Become familiar with reserved addresses (RFC 1918, 5735) Determine your network requirements Number of subnets and hosts your implementation requires Identify your base address (Starting point, class A, B, or C) Write out, and use the MB-Key and prepare to use the thumb game. Before Starting the IP Subnetting Process 29 2013 Cisco and/or its affiliates. All rights reserved. BRKCRT-9346 Cisco Public Identify the total number of subnets requiring a unique address: Unique address required for each LAN subnet Unique address required for each WAN subnet Verify how many hosts are needed per subnet Identify and create a subnet mask that accommodates the design This is where the movement of the line will extend the mask to go beyond its default (moving the mask to the right, bit by bit).