17 November 2015 RE Meyers, Ms.Ed., CCAI CCENT Test Strategies Accurate and Fast IP Address Problem Solving Part 2: Critical Reading Skills

17 November 2015 RE Meyers, Ms.Ed., CCAI Subnets and VLSM Problem Solving  This is not a presentation on how to subnet or how to develop VLSM IP addresses.  Both skills are presumed to be taught, practiced, and accomplished by now.  If you still can’t subnet or develop VLSM addresses, then you need to go back and practice those skills.  Practice is the only way to become proficient at subnetting and VLSM addressing. Very few people actually like to practice. Nobody likes to fail. Practice reduces failure to a small percentage. Your choice.

17 November 2015 RE Meyers, Ms.Ed., CCAI Subnets and VLSM Problem Solving  Given enough practice and time, networking instructors and students will be able to solve all subnet and VLSM problems on an exam.  On a certification exam, the biggest challenge is time. Certification exam time management is a critical skill for success. Spending the least amount of time on each question to arrive at fast and accurate answers is vital. Under pressure of a ticking clock, we all can choke and freeze. This lesson proposes a way to solve time-consuming subnet and VLSM problems fast and accurately. It still requires patience and practice. Did I mention practice? You must practice. A lot.

17 November 2015 RE Meyers, Ms.Ed., CCAI Critical Reading  Many complain that Cisco exams are “reading comprehension exams” and not technical exams.  Anyone who works at a help desk will confirm that clear communication is the first hurdle to solving any problem.  If you don’t understand the question, then any technical solution is lost.

17 November 2015 RE Meyers, Ms.Ed., CCAI Critical Reading: Eliminate Distracters, Find the Keys  Word problems and logical topologies always give:  Exactly what you need, Keys, to solve the problem.  More than you need, called Distracters.  The first step to quick problem solving is eliminate the Distracters and pick out the Keys to the solution.

17 November 2015 RE Meyers, Ms.Ed., CCAI IP Problem Solving: Eliminate Distracters, Find the Keys  Example:  A network engineer assigned the following addresses to serial connections on his enterprise network: /30, / /30, and /30. What class of addressing is being used? (select two) A B C RFC 1918 RFC 1919 PAT

17 November 2015 RE Meyers, Ms.Ed., CCAI IP Problem Solving: Eliminate Distracters, Find the Keys  Red distracters. Blue keys:  A network engineer assigned the following addresses to serial connections on his enterprise network: /30, / /30, and /30. What class of addressing is being used? (select 2) Serial connections: Who cares? The question is about address class not connections /30, 1.209/30, 1.202/30, 1.242/30: The third and fourth octet and CIDR do NOT determine the class of the address. 192.: The first octet number determines the IP Class x: The first octets of this IP will also tell you if it is a special reserved IP class.

17 November 2015 RE Meyers, Ms.Ed., CCAI IP Problem Solving: Use the Keys  Since you can’t highlight the PC screen, you are allowed to use pen and paper on exams.  USE THEM and write down the keys from the question The first octet number determines the IP Class. –Class C A special reserved IP class –Class C private address defined by RFC 1918

17 November 2015 RE Meyers, Ms.Ed., CCAI IP Problem Solving: Pick the Correct Answers  A network engineer assigned the following addresses to serial connections on his enterprise network: /30, / /30, and /30. What class of addressing is being used? (select 2) : AA BB CC  RFC 1918  RFC 1919  PAT Any address beginning with 192 is Class C. Addresses beginning with are private RFC 1918.

17 November 2015 RE Meyers, Ms.Ed., CCAI 1) Finding Network Addresses: Subnetting a Subnet

17 November 2015 RE Meyers, Ms.Ed., CCAI 1) Finding Network Addresses: Subnetting a Subnet  Eliminate Distracters, Find the Keys  Router names, port id’s (S0, E0)  /26  /26  “…valid VLSM network addresses for the serial link…”

17 November 2015 RE Meyers, Ms.Ed., CCAI 1) Finding Network Addresses: Use the Keys  /26 and /26 use up a lot of IP addresses.  What ranges are used and what ranges are available?  /26 means 2 bits are borrowed, so network addresses start at 0 and increment by 64: Subnet 0 = – 63 /26 Unused; Range Available Subnet 1 = – 127 /26 Used; unavailable Subnet 2 = – 191 /26 Used; unavailable Subnet 3 = – 255 /26 Unused; Range Available

17 November 2015 RE Meyers, Ms.Ed., CCAI 1) Finding Network Addresses: Use the Keys  Solve the problem  Subnet 0 = – 63 /26 Unused; Range Available Option 1: /30 increments the networks by 4 and falls inside the subnet 0 range which is available. Option 2: /30 is the next network after 4/30 and also falls inside the subnet 0 range which is available.  Subnet 1 = – 127 /26 Used; Range Unavailable XOptions 3 & 4 are inside this range and NOT available.  Subnet 2 = – 191 /26 Used; Range Unavailable XOption 5 is inside this range and NOT available

17 November 2015 RE Meyers, Ms.Ed., CCAI 1) Finding Network Addresses: Pick the Correct Answers

17 November 2015 RE Meyers, Ms.Ed., CCAI 2) Finding a Range of Hosts, Ex. A

17 November 2015 RE Meyers, Ms.Ed., CCAI 2) Finding a Range of Hosts, Ex. A  Eliminate Distracters, Find the Keys:  /20 assigned to Host A  “How many additional networked devices will this subnetwork support?”

17 November 2015 RE Meyers, Ms.Ed., CCAI 2) Finding a Range of Hosts, Ex. A: Use the Keys  /20  The IP address is not important.  /20 tells you that 12 bits are used for the host range.  2 12 – 2 = 4096 – 2 = 4094  4094 – 1 host already assigned = 4093

17 November 2015 RE Meyers, Ms.Ed., CCAI 2) Finding a Range of Hosts, Ex. A: Pick the Answer

17 November 2015 RE Meyers, Ms.Ed., CCAI 2) Finding a Range of Hosts, Ex. B

17 November 2015 RE Meyers, Ms.Ed., CCAI 2) Finding a Range of Hosts, Ex. B  Eliminate Distracters, Find the Keys  Router Serial connection and cloud  /27 is a subnetwork because of /27

17 November 2015 RE Meyers, Ms.Ed., CCAI 2) Finding a Range of Hosts, Ex. B: Use the Keys  /27  /27 indicates 3 bits were borrowed.  Network addresses start at 0 and increment by 32. Subnet 0 = – 31 /27 Subnet 1 = – 63 /27 –All host addresses from through /27are available for use.

17 November 2015 RE Meyers, Ms.Ed., CCAI 2) Finding a Range of Hosts, Ex. B: Pick the Answers All host addresses from through /27are available for use.

17 November 2015 RE Meyers, Ms.Ed., CCAI 3) Find Network Information from a Host IP

17 November 2015 RE Meyers, Ms.Ed., CCAI 3) Find Network Information from a Host IP  Eliminate Distracters, Find Keys:  Distracters are also found in answer options!  In this case, all of the answers are very distracting, and three are very wrong!  Concentrate on what you can learn from the given IP “… information…from /29”

17 November 2015 RE Meyers, Ms.Ed., CCAI 3) Find Network Information from a Host IP: Use the Keys  /29  /29 indicates 5 bits were borrowed  /29 is CIDR for subnet mask  Networks increment by 8.  0 – 7, 8 – 15, 16 – 31, … 72 – 79, 80 – 87, 88 – 95, etc.  Usable hosts per network are = 6 .93 is the 5th host on the.88 –.95 network

17 November 2015 RE Meyers, Ms.Ed., CCAI 3) Find Network Information from a Host IP: NOTE!  Use your correct work to eliminate wrong options Broadcast addresses are NEVER even numbers! /29 indicates 5 bits were borrowed /29 is CIDR for subnet mask Networks increment by 8. 0 – 7, 8 – 15, 16 – 31…72 – 79, 80 – 87, 88 – 95, etc. Usable hosts per network are = 6.93 is the 5th host on the.88 –.95 network

17 November 2015 RE Meyers, Ms.Ed., CCAI 4) Solving a Configuration Problem, Ex. A

17 November 2015 RE Meyers, Ms.Ed., CCAI 4) Solving a Configuration Problem, Ex. A  Eliminate Distracters, Find Keys:  Few real distracters – ignore the router/cloud connection.  Keys Router Ethernet address: /27 Host configuration:

17 November 2015 RE Meyers, Ms.Ed., CCAI 4) Solving a Configuration Problem, Ex. A: Use Keys  Compare router port and PC configuration:  IP of gateway matches router port.  Router CIDR /27 means 3 bits are borrowed PC and router SM match.  CIDR /27 means networks increment by 32 0 – 31, 32 – 63, 64 – 95, etc. IP of router port is on subnet 0. IP of PC is on subnet 1.

17 November 2015 RE Meyers, Ms.Ed., CCAI 4) Solving a Configuration Problem, Ex. A: Pick Answer

17 November 2015 RE Meyers, Ms.Ed., CCAI 4) Solving a Configuration Problem, Ex. B

17 November 2015 RE Meyers, Ms.Ed., CCAI 4) Solving a Configuration Problem, Ex. B  Eliminate Distracters, Find Keys:  H2 and H1 can’t communicate H1= /28 H2= /28  Switch is a distracter.

17 November 2015 RE Meyers, Ms.Ed., CCAI 4) Solving a Configuration Problem, Ex. B: Use Keys  All you have are host IP’s and CIDR. So one is wrong!  CIDR /28 matches on both. /28 borrows 4 bits, so networks increment by 16 0 – 15, 16 – 32, 32 – 47, 48 – 63, etc  H is on subnet 1  H is on subnet 2  Host IP’s are not on the same subnet.

17 November 2015 RE Meyers, Ms.Ed., CCAI 4) Solving a Configuration Problem, Ex. B: Pick Answer

17 November 2015 RE Meyers, Ms.Ed., CCAI 5) Subnetting a Subnet: Applied VLSM  A network engineer is implementing a network design using VLSM for network /24. The engineer has decided to take one of the subnets, /28, and subnet it further for point-to-point serial link addresses.  What is the maximum number of subnets that can be created from the /28 subnet for serial connections?

17 November 2015 RE Meyers, Ms.Ed., CCAI 5) Subnetting a Subnet: Applied VLSM  Distracters and Keys  A network engineer is implementing a network design using VLSM for network /24. The engineer has decided to take one of the subnets, /28, and subnet it further for point-to-point serial link addresses. What is the maximum number of subnets that can be created from the /28 subnet for serial connections?

17 November 2015 RE Meyers, Ms.Ed., CCAI 5) Subnetting a Subnet: Applied VLSM:Use Keys  /24  Complete Class C private address is used  /28 /28 = 4 bits borrowed, subnets increment by /28 is the subnetwork address of the range – 31/28.  Point to point serial connections require only 2 hosts /30 CIDR will provide 2 useable hosts per network. Start at and end at with /30.16 –.19,.20 –.23,.24 –.27,.28 –.31 Four subnets are available for serial connections in the /28 network.

17 November 2015 RE Meyers, Ms.Ed., CCAI 5) Subnetting a Subnet: Applied VLSM: Pick Answer  A network engineer is implementing a network design using VLSM for network /24. The engineer has decided to take one of the subnets, /28, and subnet it further for point-to-point serial link addresses. What is the maximum number of subnets that can be created from the /28 subnet for serial connections?  Four

17 November 2015 RE Meyers, Ms.Ed., CCAI Practice!

17 November 2015 RE Meyers, Ms.Ed., CCAI End