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IPv4.Overview

IPv4.Overview 34 KB
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  11. text=IPv4 Addressing%0a%0aEvery device on the Internet needs a unique address to communicate with each other.%0aThis address is called the Internet Protocol (IP) Address. %0a%0aAn IPv4 address is 32 bits long -- thirty-two 1s and 0s. For example:%0a%0a|| border=1 width=100%25 class="sortable simpletable"%0a||! IPv4 Address 192.168.0.1 ||%0a|| Decimal || 192 || 168 || 0 || 1 ||%0a|| Binary || 1100 0000 || 1010 1000 || 0000 0000 || 0000 0001 ||%0a%0aand is expressed in 4 doted octets format. An (unsigned) octet is 8 bits in size thus the smallest value (where all 8 bits are 0) is 0 (in decimal) while the largest value (while all 8 bits are 1) is 255.%0a%0aIPv6 address however is 128 bits long and is expressed in 8 groups of 4 hexadecimal digits. A hexadecimal digit can hold up to 16 unique values thus it is represented in 0 (when all 4 bits are 0) and F (when all 4 bits are 1). %0a%0aIP prefix is an IP address expressed in CIDR notation. It carries two (2) information important information for routers on the internet to be able to deliver the traffic to its destination. These information are: (a) Network ID (or network prefix) and (b) Host ID. Network ID represents which network the address belongs to while Host ID represents end device (within the network) it is intended for. Keep in mind that the last address in a network is used as broadcast address (sending traffic to all the hosts within the same network).%0a%0aThe prefix in CIDR notation indicates the number of bits (from left to right) is used to identify the network. Following are examples of IPv4 prefix in CIRD notation:%0a%0aExample 1: a prefix of 192.168.0.1/24 dictates that the first 24 bits represents the network while the remaining 8 (32-8) bits represents the host. In this case Network ID is 192.168.0.0 and the host address starts from 192.168.0.0 and ends at 192.168.0.254 (.255 is broadcast).%0a%0aExample 2: a prefix of 192.168.0.129/25 dictates that the first 25 bits represents the network and therefore the Network ID is 192.168.0.128 and the host address starts from 192.168.0.129 and ends at 192.168.0.254 (.255 is broadcast). This is because the first 25 bits of 192.168.0.129 (11000000.10101000.00000000.10000001) summed up to 192.168.0.128 (11000000.10101000.00000000.10000000).%0a%0aExample 3: a prefix of 192.168.3.88/23 dictate that the first 23 bits represents the network and therefore the Network ID is 192.168.2.0 and the host address starts from 192.168.2.1 and ends at 192.168.3.254 (.255 is broadcast). This is because the first 23 bits of 192.168.3.88 (11000000.10101000.00000011.00101100) summed up to 192.168.2.0 (11000000.10101000.00000010.00000000).%0a%0aExample 4: a prefix of 192.168.123.123/32 dictates that the first 32 bits represents the network and therefore both the Network ID and Host ID will be 192.168.123.123.%0a%0aWhile it is true that any IP address (if it follows the rules above) can be used as valid IP address, however some of the addresses are reserved for special purpose. Table below lists all the IP prefixes that have special purpose are not routable over the internet. %0a%0a|| border=1 width=100%25 class="sortable simpletable"%0a||! Prefix ||! Description ||%0a|| 0.0.0.0/8 || "This" network ||%0a|| 10.0.0.0/8 || Private-use networks ||%0a|| 100.64.0.0/10 || Carrier-grade NAT ||%0a|| 127.0.0.0/8 || Loopback ||%0a|| 127.0.53.53 || Name collision occurrence ||%0a|| 169.254.0.0/16 || Link local ||%0a|| 172.16.0.0/12 || Private-use networks ||%0a|| 192.0.0.0/24 || IETF protocol assignments ||%0a|| 192.0.2.0/24 || TEST-NET-1 ||%0a|| 192.168.0.0/16 || Private-use networks ||%0a|| 198.18.0.0/15 || Network interconnect device benchmark testing ||%0a|| 198.51.100.0/24 || TEST-NET-2 ||%0a|| 203.0.113.0/24 || TEST-NET-3 ||%0a|| 224.0.0.0/4 || Multicast ||%0a|| 240.0.0.0/4 || Reserved for future use ||%0a|| 255.255.255.255/32 ||Limited broadcast ||%0a%0aBelow is a table to inter-convert between CIDR and sub net mask:%0a%0a|| border=1 width=100%25 class="sortable simpletable"%0a||! CIDR prefix ||! Sub net mask ||! Number of IP addresses ||%0a|| /0 || 0.0.0.0 || 4,294,967,296 ||%0a|| /1 || 128.0.0.0 || 2,147,483,648 ||%0a|| /2 || 192.0.0.0 || 1,073,741,824 ||%0a|| /3 || 224.0.0.0 || 536,870,912 ||%0a|| /4 || 240.0.0.0 || 268,435,456 ||%0a|| /5 || 248.0.0.0 || 134,217,728 ||%0a|| /6 || 252.0.0.0 || 67,108,864 ||%0a|| /7 || 254.0.0.0 || 33,554,432 ||%0a|| /8 || 255.0.0.0 || 16,777,216 ||%0a|| /9 || 255.128.0.0 || 8,388,608 ||%0a|| /10 || 255.192.0.0 || 4,194,304 ||%0a|| /11 || 255.224.0.0 || 2,097,152 ||%0a|| /12 || 255.240.0.0 || 1,048,576 ||%0a|| /13 || 255.248.0.0 || 524,288 ||%0a|| /14 || 255.252.0.0 || 262,144 ||%0a|| /15 || 255.254.0.0 || 131,072 ||%0a|| /16 || 255.255.0.0 || 65,536 ||%0a|| /17 || 255.255.128.0 || 32,768 ||%0a|| /18 || 255.255.192.0 || 16,384 ||%0a|| /19 || 255.255.224.0 || 8,192 ||%0a|| /20 || 255.255.240.0 || 4,096 ||%0a|| /21 || 255.255.248.0 || 2,048 ||%0a|| /22 || 255.255.252.0 || 1,024 ||%0a|| /23 || 255.255.254.0 || 512 ||%0a|| /24 || 255.255.255.0 || 256 ||%0a|| /25 || 255.255.255.128 || 128 ||%0a|| /26 || 255.255.255.192 || 64 ||%0a|| /27 || 255.255.255.224 || 32 ||%0a|| /28 || 255.255.255.240 || 16 ||%0a|| /29 || 255.255.255.248 || 8 ||%0a|| /30 || 255.255.255.252 || 4 ||%0a|| /31 || 255.255.255.254 || 2 ||%0a|| /32 || 255.255.255.255 || 1 ||%0a
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  14. diff:1623319985:1623319457:=8,9c8%0a%3c || border=1 width=100%25 class="sortable simpletable"%0a%3c ||! IPv4 Address 192.168.0.1 ||%0a---%0a> 192.168.0.1%0a
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  15. host:1623319985=38.81.163.143
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  16. author:1623319457=jrmu
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  17. diff:1623319457:1623319365:=10c10%0a%3c || Binary || 1100 0000 || 1010 1000 || 0000 0000 || 0000 0001 ||%0a---%0a> || Binary || 1100 0000 || 1010 1000 || 0000 0000 || 0001 ||%0a
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  18. host:1623319457=38.81.163.143
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  20. diff:1623319365:1623318764:=3,12c3,5%0a%3c Every device on the Internet needs a unique address to communicate with each other.%0a%3c This address is called the Internet Protocol (IP) Address. %0a%3c %0a%3c An IPv4 address is 32 bits long -- thirty-two 1s and 0s. For example:%0a%3c %0a%3c 192.168.0.1%0a%3c || Decimal || 192 || 168 || 0 || 1 ||%0a%3c || Binary || 1100 0000 || 1010 1000 || 0000 0000 || 0001 ||%0a%3c %0a%3c and is expressed in 4 doted octets format. An (unsigned) octet is 8 bits in size thus the smallest value (where all 8 bits are 0) is 0 (in decimal) while the largest value (while all 8 bits are 1) is 255.%0a---%0a> Every device on the network requires a unique address to communicate to each other. This address is also known as Internet Protocol (IP) Address. In computer networking, IP address is usually written in CIDR (classless inter-domain routing) notation or subnet mask because IP address alone does not carry enough information for the traffic to be routed over the internet correctly. Both CIDR notation and subnet mask are interchangeable. See below table for conversion.%0a> %0a> An IPv4 address is 32 bits long and is expressed in 4 doted octets format. An (unsigned) octet is 8 bits in size thus the smallest value (where all 8 bits are 0) is 0 (in decimal) while the largest value (while all 8 bits are 1) is 255.%0a
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  23. diff:1623318764:1623318665:=23d22%0a%3c || border=1 width=100%25 class="sortable simpletable"%0a29,41c28,40%0a%3c || 127.0.53.53 || Name collision occurrence ||%0a%3c || 169.254.0.0/16 || Link local ||%0a%3c || 172.16.0.0/12 || Private-use networks ||%0a%3c || 192.0.0.0/24 || IETF protocol assignments ||%0a%3c || 192.0.2.0/24 || TEST-NET-1 ||%0a%3c || 192.168.0.0/16 || Private-use networks ||%0a%3c || 198.18.0.0/15 || Network interconnect device benchmark testing ||%0a%3c || 198.51.100.0/24 || TEST-NET-2 ||%0a%3c || 203.0.113.0/24 || TEST-NET-3 ||%0a%3c || 224.0.0.0/4 || Multicast ||%0a%3c || 240.0.0.0/4 || Reserved for future use ||%0a%3c || 255.255.255.255/32 ||Limited broadcast ||%0a%3c %0a---%0a> ||127.0.53.53 || Name collision occurrence ||%0a> ||169.254.0.0/16 || Link local ||%0a> ||172.16.0.0/12 || Private-use networks ||%0a> ||192.0.0.0/24 || IETF protocol assignments ||%0a> ||192.0.2.0/24 || TEST-NET-1 ||%0a> ||192.168.0.0/16 || Private-use networks ||%0a> ||198.18.0.0/15 || Network interconnect device benchmark testing ||%0a> ||198.51.100.0/24 || TEST-NET-2 ||%0a> ||203.0.113.0/24 || TEST-NET-3 ||%0a> ||224.0.0.0/4 || Multicast ||%0a> ||240.0.0.0/4 || Reserved for future use ||%0a> ||255.255.255.255/32 ||Limited broadcast ||%0a> %0a44,45c43%0a%3c || border=1 width=100%25 class="sortable simpletable"%0a%3c ||! CIDR prefix ||! Sub net mask ||! Number of IP addresses ||%0a---%0a> || CIDR prefix || Sub net mask || Number of IP addresses ||%0a
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  24. host:1623318764=38.81.163.143
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  25. author:1623318665=jrmu
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  26. diff:1623318665:1623318003:=23,40c23,57%0a%3c ||! Prefix ||! Description ||%0a%3c || 0.0.0.0/8 || "This" network ||%0a%3c || 10.0.0.0/8 || Private-use networks ||%0a%3c || 100.64.0.0/10 || Carrier-grade NAT ||%0a%3c || 127.0.0.0/8 || Loopback ||%0a%3c ||127.0.53.53 || Name collision occurrence ||%0a%3c ||169.254.0.0/16 || Link local ||%0a%3c ||172.16.0.0/12 || Private-use networks ||%0a%3c ||192.0.0.0/24 || IETF protocol assignments ||%0a%3c ||192.0.2.0/24 || TEST-NET-1 ||%0a%3c ||192.168.0.0/16 || Private-use networks ||%0a%3c ||198.18.0.0/15 || Network interconnect device benchmark testing ||%0a%3c ||198.51.100.0/24 || TEST-NET-2 ||%0a%3c ||203.0.113.0/24 || TEST-NET-3 ||%0a%3c ||224.0.0.0/4 || Multicast ||%0a%3c ||240.0.0.0/4 || Reserved for future use ||%0a%3c ||255.255.255.255/32 ||Limited broadcast ||%0a%3c %0a---%0a> Prefix%0a> Description%0a> 0.0.0.0/8%0a> "This" network%0a> 10.0.0.0/8%0a> Private-use networks%0a> 100.64.0.0/10%0a> Carrier-grade NAT%0a> 127.0.0.0/8%0a> Loopback%0a> 127.0.53.53%0a> Name collision occurrence%0a> 169.254.0.0/16%0a> Link local%0a> 172.16.0.0/12%0a> Private-use networks%0a> 192.0.0.0/24%0a> IETF protocol assignments%0a> 192.0.2.0/24%0a> TEST-NET-1%0a> 192.168.0.0/16%0a> Private-use networks%0a> 198.18.0.0/15%0a> Network interconnect device benchmark testing%0a> 198.51.100.0/24%0a> TEST-NET-2%0a> 203.0.113.0/24%0a> TEST-NET-3%0a> 224.0.0.0/4%0a> Multicast%0a> 240.0.0.0/4%0a> Reserved for future use%0a> 255.255.255.255/32%0a> Limited broadcast%0a> %0a42,76c59,162%0a%3c %0a%3c || CIDR prefix || Sub net mask || Number of IP addresses ||%0a%3c || /0 || 0.0.0.0 || 4,294,967,296 ||%0a%3c || /1 || 128.0.0.0 || 2,147,483,648 ||%0a%3c || /2 || 192.0.0.0 || 1,073,741,824 ||%0a%3c || /3 || 224.0.0.0 || 536,870,912 ||%0a%3c || /4 || 240.0.0.0 || 268,435,456 ||%0a%3c || /5 || 248.0.0.0 || 134,217,728 ||%0a%3c || /6 || 252.0.0.0 || 67,108,864 ||%0a%3c || /7 || 254.0.0.0 || 33,554,432 ||%0a%3c || /8 || 255.0.0.0 || 16,777,216 ||%0a%3c || /9 || 255.128.0.0 || 8,388,608 ||%0a%3c || /10 || 255.192.0.0 || 4,194,304 ||%0a%3c || /11 || 255.224.0.0 || 2,097,152 ||%0a%3c || /12 || 255.240.0.0 || 1,048,576 ||%0a%3c || /13 || 255.248.0.0 || 524,288 ||%0a%3c || /14 || 255.252.0.0 || 262,144 ||%0a%3c || /15 || 255.254.0.0 || 131,072 ||%0a%3c || /16 || 255.255.0.0 || 65,536 ||%0a%3c || /17 || 255.255.128.0 || 32,768 ||%0a%3c || /18 || 255.255.192.0 || 16,384 ||%0a%3c || /19 || 255.255.224.0 || 8,192 ||%0a%3c || /20 || 255.255.240.0 || 4,096 ||%0a%3c || /21 || 255.255.248.0 || 2,048 ||%0a%3c || /22 || 255.255.252.0 || 1,024 ||%0a%3c || /23 || 255.255.254.0 || 512 ||%0a%3c || /24 || 255.255.255.0 || 256 ||%0a%3c || /25 || 255.255.255.128 || 128 ||%0a%3c || /26 || 255.255.255.192 || 64 ||%0a%3c || /27 || 255.255.255.224 || 32 ||%0a%3c || /28 || 255.255.255.240 || 16 ||%0a%3c || /29 || 255.255.255.248 || 8 ||%0a%3c || /30 || 255.255.255.252 || 4 ||%0a%3c || /31 || 255.255.255.254 || 2 ||%0a%3c || /32 || 255.255.255.255 || 1 ||%0a---%0a> CIDR prefix%0a> Sub net mask%0a> Number of IP addresses%0a> /0%0a> 0.0.0.0%0a> 4,294,967,296%0a> /1%0a> 128.0.0.0%0a> 2,147,483,648%0a> /2%0a> 192.0.0.0%0a> 1,073,741,824%0a> /3%0a> 224.0.0.0%0a> 536,870,912%0a> /4%0a> 240.0.0.0%0a> 268,435,456%0a> /5%0a> 248.0.0.0%0a> 134,217,728%0a> /6%0a> 252.0.0.0%0a> 67,108,864%0a> /7%0a> 254.0.0.0%0a> 33,554,432%0a> /8%0a> 255.0.0.0%0a> 16,777,216%0a> /9%0a> 255.128.0.0%0a> 8,388,608%0a> /10%0a> 255.192.0.0%0a> 4,194,304%0a> /11%0a> 255.224.0.0%0a> 2,097,152%0a> /12%0a> 255.240.0.0%0a> 1,048,576%0a> /13%0a> 255.248.0.0%0a> 524,288%0a> /14%0a> 255.252.0.0%0a> 262,144%0a> /15%0a> 255.254.0.0%0a> 131,072%0a> /16%0a> 255.255.0.0%0a> 65,536%0a> /17%0a> 255.255.128.0%0a> 32,768%0a> /18%0a> 255.255.192.0%0a> 16,384%0a> /19%0a> 255.255.224.0%0a> 8,192%0a> /20%0a> 255.255.240.0%0a> 4,096%0a> /21%0a> 255.255.248.0%0a> 2,048%0a> /22%0a> 255.255.252.0%0a> 1,024%0a> /23%0a> 255.255.254.0%0a> 512%0a> /24%0a> 255.255.255.0%0a> 256%0a> /25%0a> 255.255.255.128%0a> 128%0a> /26%0a> 255.255.255.192%0a> 64%0a> /27%0a> 255.255.255.224%0a> 32%0a> /28%0a> 255.255.255.240%0a> 16%0a> /29%0a> 255.255.255.248%0a> 8%0a> /30%0a> 255.255.255.252%0a> 4%0a> /31%0a> 255.255.255.254%0a> 2%0a> /32%0a> 255.255.255.255%0a> 1%0a> %0a> %0a
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  27. host:1623318665=38.81.163.143
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  28. author:1623318003=jrmu
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  29. diff:1623318003:1616857973:=1,162d0%0a%3c IPv4 Addressing%0a%3c %0a%3c Every device on the network requires a unique address to communicate to each other. This address is also known as Internet Protocol (IP) Address. In computer networking, IP address is usually written in CIDR (classless inter-domain routing) notation or subnet mask because IP address alone does not carry enough information for the traffic to be routed over the internet correctly. Both CIDR notation and subnet mask are interchangeable. See below table for conversion.%0a%3c %0a%3c An IPv4 address is 32 bits long and is expressed in 4 doted octets format. An (unsigned) octet is 8 bits in size thus the smallest value (where all 8 bits are 0) is 0 (in decimal) while the largest value (while all 8 bits are 1) is 255.%0a%3c %0a%3c IPv6 address however is 128 bits long and is expressed in 8 groups of 4 hexadecimal digits. A hexadecimal digit can hold up to 16 unique values thus it is represented in 0 (when all 4 bits are 0) and F (when all 4 bits are 1). %0a%3c %0a%3c IP prefix is an IP address expressed in CIDR notation. It carries two (2) information important information for routers on the internet to be able to deliver the traffic to its destination. These information are: (a) Network ID (or network prefix) and (b) Host ID. Network ID represents which network the address belongs to while Host ID represents end device (within the network) it is intended for. Keep in mind that the last address in a network is used as broadcast address (sending traffic to all the hosts within the same network).%0a%3c %0a%3c The prefix in CIDR notation indicates the number of bits (from left to right) is used to identify the network. Following are examples of IPv4 prefix in CIRD notation:%0a%3c %0a%3c Example 1: a prefix of 192.168.0.1/24 dictates that the first 24 bits represents the network while the remaining 8 (32-8) bits represents the host. In this case Network ID is 192.168.0.0 and the host address starts from 192.168.0.0 and ends at 192.168.0.254 (.255 is broadcast).%0a%3c %0a%3c Example 2: a prefix of 192.168.0.129/25 dictates that the first 25 bits represents the network and therefore the Network ID is 192.168.0.128 and the host address starts from 192.168.0.129 and ends at 192.168.0.254 (.255 is broadcast). This is because the first 25 bits of 192.168.0.129 (11000000.10101000.00000000.10000001) summed up to 192.168.0.128 (11000000.10101000.00000000.10000000).%0a%3c %0a%3c Example 3: a prefix of 192.168.3.88/23 dictate that the first 23 bits represents the network and therefore the Network ID is 192.168.2.0 and the host address starts from 192.168.2.1 and ends at 192.168.3.254 (.255 is broadcast). This is because the first 23 bits of 192.168.3.88 (11000000.10101000.00000011.00101100) summed up to 192.168.2.0 (11000000.10101000.00000010.00000000).%0a%3c %0a%3c Example 4: a prefix of 192.168.123.123/32 dictates that the first 32 bits represents the network and therefore both the Network ID and Host ID will be 192.168.123.123.%0a%3c %0a%3c While it is true that any IP address (if it follows the rules above) can be used as valid IP address, however some of the addresses are reserved for special purpose. Table below lists all the IP prefixes that have special purpose are not routable over the internet. %0a%3c %0a%3c Prefix%0a%3c Description%0a%3c 0.0.0.0/8%0a%3c "This" network%0a%3c 10.0.0.0/8%0a%3c Private-use networks%0a%3c 100.64.0.0/10%0a%3c Carrier-grade NAT%0a%3c 127.0.0.0/8%0a%3c Loopback%0a%3c 127.0.53.53%0a%3c Name collision occurrence%0a%3c 169.254.0.0/16%0a%3c Link local%0a%3c 172.16.0.0/12%0a%3c Private-use networks%0a%3c 192.0.0.0/24%0a%3c IETF protocol assignments%0a%3c 192.0.2.0/24%0a%3c TEST-NET-1%0a%3c 192.168.0.0/16%0a%3c Private-use networks%0a%3c 198.18.0.0/15%0a%3c Network interconnect device benchmark testing%0a%3c 198.51.100.0/24%0a%3c TEST-NET-2%0a%3c 203.0.113.0/24%0a%3c TEST-NET-3%0a%3c 224.0.0.0/4%0a%3c Multicast%0a%3c 240.0.0.0/4%0a%3c Reserved for future use%0a%3c 255.255.255.255/32%0a%3c Limited broadcast%0a%3c %0a%3c Below is a table to inter-convert between CIDR and sub net mask:%0a%3c CIDR prefix%0a%3c Sub net mask%0a%3c Number of IP addresses%0a%3c /0%0a%3c 0.0.0.0%0a%3c 4,294,967,296%0a%3c /1%0a%3c 128.0.0.0%0a%3c 2,147,483,648%0a%3c /2%0a%3c 192.0.0.0%0a%3c 1,073,741,824%0a%3c /3%0a%3c 224.0.0.0%0a%3c 536,870,912%0a%3c /4%0a%3c 240.0.0.0%0a%3c 268,435,456%0a%3c /5%0a%3c 248.0.0.0%0a%3c 134,217,728%0a%3c /6%0a%3c 252.0.0.0%0a%3c 67,108,864%0a%3c /7%0a%3c 254.0.0.0%0a%3c 33,554,432%0a%3c /8%0a%3c 255.0.0.0%0a%3c 16,777,216%0a%3c /9%0a%3c 255.128.0.0%0a%3c 8,388,608%0a%3c /10%0a%3c 255.192.0.0%0a%3c 4,194,304%0a%3c /11%0a%3c 255.224.0.0%0a%3c 2,097,152%0a%3c /12%0a%3c 255.240.0.0%0a%3c 1,048,576%0a%3c /13%0a%3c 255.248.0.0%0a%3c 524,288%0a%3c /14%0a%3c 255.252.0.0%0a%3c 262,144%0a%3c /15%0a%3c 255.254.0.0%0a%3c 131,072%0a%3c /16%0a%3c 255.255.0.0%0a%3c 65,536%0a%3c /17%0a%3c 255.255.128.0%0a%3c 32,768%0a%3c /18%0a%3c 255.255.192.0%0a%3c 16,384%0a%3c /19%0a%3c 255.255.224.0%0a%3c 8,192%0a%3c /20%0a%3c 255.255.240.0%0a%3c 4,096%0a%3c /21%0a%3c 255.255.248.0%0a%3c 2,048%0a%3c /22%0a%3c 255.255.252.0%0a%3c 1,024%0a%3c /23%0a%3c 255.255.254.0%0a%3c 512%0a%3c /24%0a%3c 255.255.255.0%0a%3c 256%0a%3c /25%0a%3c 255.255.255.128%0a%3c 128%0a%3c /26%0a%3c 255.255.255.192%0a%3c 64%0a%3c /27%0a%3c 255.255.255.224%0a%3c 32%0a%3c /28%0a%3c 255.255.255.240%0a%3c 16%0a%3c /29%0a%3c 255.255.255.248%0a%3c 8%0a%3c /30%0a%3c 255.255.255.252%0a%3c 4%0a%3c /31%0a%3c 255.255.255.254%0a%3c 2%0a%3c /32%0a%3c 255.255.255.255%0a%3c 1%0a%3c %0a%3c %0a
    30. 

  30. host:1623318003=38.81.163.143
    31. 

  31. author:1616857973=chewy
    32. 

  32. diff:1616857973:1616857608:=0a1,92%0a> !!Understanding IPv4 Addressing%0a> %0a> IPv4 addresses are 32-bit numbers that are typically displayed in dotted decimal notation. A 32-bit address contains two primary parts: the network prefix and the host number.%0a> %0a> All hosts within a single network share the same network address. Each host also has an address that uniquely identifies it. Depending on the scope of the network and the type of device, the address is either globally or locally unique. Devices that are visible to users outside the network (webservers, for example) must have a globally unique IP address. Devices that are visible only within the network must have locally unique IP addresses.%0a> %0a> IP addresses are assigned by a central numbering authority called the Internet Assigned Numbers Authority (IANA). IANA ensures that addresses are globally unique where needed and has a large address space reserved for use by devices not visible outside their own networks.%0a> %0a> !!IPv4 Classful Addressing%0a> %0a> To provide flexibility in the number of addresses distributed to networks of different sizes, 4-octet (32-bit) IP addresses were originally divided into three different categories or classes: class A, class B, and class C. Each address class specifies a different number of bits for its network prefix and host number:%0a> %0a> *    Class A addresses use only the first byte (octet) to specify the network prefix, leaving 3 bytes to define individual host numbers.%0a> %0a> *    Class B addresses use the first 2 bytes to specify the network prefix, leaving 2 bytes to define host addresses.%0a> %0a> *    Class C addresses use the first 3 bytes to specify the network prefix, leaving only the last byte to identify hosts.%0a> %0a> In binary format, with an x representing each bit in the host number, the three address classes can be represented as follows:%0a> %0a> %0a> %25center%2500000000 xxxxxxxx xxxxxxxx xxxxxxxx (Class A)%0a> %0a> %25center%2500000000 00000000 xxxxxxxx xxxxxxxx (Class B)%0a> %0a> %25center%2500000000 00000000 00000000 xxxxxxxx (Class C)%0a> %0a> %0a> Because each bit (x) in a host number can have a 0 or 1 value, each represents a power of 2. For example, if only 3 bits are available for specifying the host number, only the following host numbers are possible:%0a> %0a> %25center%25111 110 101 100 011 010 001 000%0a> %0a> In each IP address class, the number of host-number bits raised to the power of 2 indicates how many host numbers can be created for a particular network prefix. Class A addresses have 224 (or 16,777,216) possible host numbers, class B addresses have 216 (or 65,536) host numbers, and class C addresses have 28 (or 256) possible host numbers.%0a> %0a> !!IPv4 Dotted Decimal Notation%0a> %0a> The 32-bit IPv4 addresses are most often expressed in dotted decimal notation, in which each octet (or byte) is treated as a separate number. Within an octet, the rightmost bit represents 20 (or 1), increasing to the left until the first bit in the octet is 27 (or 128). Following are IP addresses in binary format and their dotted decimal equivalents:%0a> %0a> %25center%2511010000 01100010 11000000 10101010 = 208.98.192.170%0a> %0a> %25center%2501110110 00001111 11110000 01010101 = 118.15.240.85%0a> %0a> %25center%2500110011 11001100 00111100 00111011 = 51.204.60.59%0a> %0a> %0a> !!IPv4 Subnetting%0a> %0a> %0a> Because of the physical and architectural limitations on the size of networks, you often must break large networks into smaller subnetworks. Within a network, each wire or ring requires its own network number and identifying subnet address.%0a> %0a> Figure 1 shows two subnets in a network.%0a> %0a> Figure 1: Subnets in a Network%0a> %0a> %25center%25Attach:IPV4/IPV4.gif%0a> %0a> %0a> Figure 1 shows three devices connected to one subnet and three more devices connected to a second subnet. Collectively, the six devices and two subnets make up the larger network. In this example, the network is assigned the network prefix 192.14.0.0, a class C address. Each device has an IP address that falls within this network prefix.%0a> %0a> In addition to sharing a network prefix (the first two octets), the devices on each subnet share a third octet. The third octet identifies the subnet. All devices on a subnet must have the same subnet address. In this case, the alpha subnet has the IP address 192.14.126.0 and the beta subnet has the IP address 192.14.17.0.%0a> %0a> The subnet address 192.14.17.0 can be represented as follows in binary notation:%0a> %0a> %0a> %25center%2511000000 . 00001110 . 00010001 . xxxxxxxx%0a> %0a> %0a> Because the first 24 bits in the 32-bit address identify the subnet, the last 8 bits are not significant. To indicate the subnet, the address is written as 192.14.17.0/24 (or just 192.14.17/24). The /24 is the subnet mask (sometimes shown as 255.255.255.0).%0a> %0a> %0a> !!IPv4 Variable-Length Subnet Masks%0a> %0a> %0a> Traditionally, subnets were divided by address class. Subnets had either 8, 16, or 24 significant bits, corresponding to 224, 216, or 28 possible hosts. As a result, an entire /16 subnet had to be allocated for a network that required only 400 addresses, wasting 65,136 (216 – 400 = 65,136) addresses.%0a> %0a> To help allocate address spaces more efficiently, variable-length subnet masks (VLSMs) were introduced. Using VLSM, network architects can allocate more precisely the number of addresses required for a particular subnet.%0a> %0a> For example, suppose a network with the prefix 192.14.17/24 is divided into two smaller subnets, one consisting of 18 devices and the other of 46 devices.%0a> %0a> To accommodate 18 devices, the first subnet must have 25 (32) host numbers. Having 5 bits assigned to the host number leaves 27 bits of the 32-bit address for the subnet. The IP address of the first subnet is therefore 192.14.17.128/27, or the following in binary notation:%0a> %0a> %0a> %25center%2511000000 . 00001110 . 00010001 . 100xxxxx%0a> %0a> The subnet mask includes 27 significant digits.%0a> %0a> To create the second subnet of 46 devices, the network must accommodate 26 (64) host numbers. The IP address of the second subnet is 192.14.17.64/26, or %0a> %0a> %25center%2511000000 . 00001110 . 00010001 . 01xxxxxx%0a> %0a> %0a> By assigning address bits within the larger /24 subnet mask, you create two smaller subnets that use the allocated address space more efficiently.%0a\ No newline at end of file%0a
    33. 

  33. host:1616857973=2a02:1205:34c1:94e0:1519:e2fd:b709:801e
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  35. diff:1616857608:1616857583:=55c55%0a%3c %25center%25Attach:IPV4/IPV4.gif%0a---%0a> Attach:IPV4/IPV4.gif%0a
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  36. host:1616857608=2a02:1205:34c1:94e0:1519:e2fd:b709:801e
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    38. 

  38. diff:1616857583:1616857374:=55,92c55%0a%3c Attach:IPV4/IPV4.gif%0a%3c %0a%3c %0a%3c Figure 1 shows three devices connected to one subnet and three more devices connected to a second subnet. Collectively, the six devices and two subnets make up the larger network. In this example, the network is assigned the network prefix 192.14.0.0, a class C address. Each device has an IP address that falls within this network prefix.%0a%3c %0a%3c In addition to sharing a network prefix (the first two octets), the devices on each subnet share a third octet. The third octet identifies the subnet. All devices on a subnet must have the same subnet address. In this case, the alpha subnet has the IP address 192.14.126.0 and the beta subnet has the IP address 192.14.17.0.%0a%3c %0a%3c The subnet address 192.14.17.0 can be represented as follows in binary notation:%0a%3c %0a%3c %0a%3c %25center%2511000000 . 00001110 . 00010001 . xxxxxxxx%0a%3c %0a%3c %0a%3c Because the first 24 bits in the 32-bit address identify the subnet, the last 8 bits are not significant. To indicate the subnet, the address is written as 192.14.17.0/24 (or just 192.14.17/24). The /24 is the subnet mask (sometimes shown as 255.255.255.0).%0a%3c %0a%3c %0a%3c !!IPv4 Variable-Length Subnet Masks%0a%3c %0a%3c %0a%3c Traditionally, subnets were divided by address class. Subnets had either 8, 16, or 24 significant bits, corresponding to 224, 216, or 28 possible hosts. As a result, an entire /16 subnet had to be allocated for a network that required only 400 addresses, wasting 65,136 (216 – 400 = 65,136) addresses.%0a%3c %0a%3c To help allocate address spaces more efficiently, variable-length subnet masks (VLSMs) were introduced. Using VLSM, network architects can allocate more precisely the number of addresses required for a particular subnet.%0a%3c %0a%3c For example, suppose a network with the prefix 192.14.17/24 is divided into two smaller subnets, one consisting of 18 devices and the other of 46 devices.%0a%3c %0a%3c To accommodate 18 devices, the first subnet must have 25 (32) host numbers. Having 5 bits assigned to the host number leaves 27 bits of the 32-bit address for the subnet. The IP address of the first subnet is therefore 192.14.17.128/27, or the following in binary notation:%0a%3c %0a%3c %0a%3c %25center%2511000000 . 00001110 . 00010001 . 100xxxxx%0a%3c %0a%3c The subnet mask includes 27 significant digits.%0a%3c %0a%3c To create the second subnet of 46 devices, the network must accommodate 26 (64) host numbers. The IP address of the second subnet is 192.14.17.64/26, or %0a%3c %0a%3c %25center%2511000000 . 00001110 . 00010001 . 01xxxxxx%0a%3c %0a%3c %0a%3c By assigning address bits within the larger /24 subnet mask, you create two smaller subnets that use the allocated address space more efficiently.%0a\ No newline at end of file%0a---%0a> Attach:IPV4/IPV4.gif%0a\ No newline at end of file%0a
    39. 

  39. host:1616857583=2a02:1205:34c1:94e0:1519:e2fd:b709:801e
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  40. author:1616857374=chewy
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  41. diff:1616857374:1616857344:=47a48,49%0a> %0a> IPv4 Subnetting%0a
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  42. host:1616857374=2a02:1205:34c1:94e0:1519:e2fd:b709:801e
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  44. diff:1616857344:1616857260:=47,55d46%0a%3c %0a%3c %0a%3c IPv4 Subnetting%0a%3c %0a%3c Because of the physical and architectural limitations on the size of networks, you often must break large networks into smaller subnetworks. Within a network, each wire or ring requires its own network number and identifying subnet address.%0a%3c %0a%3c Figure 1 shows two subnets in a network.%0a%3c %0a%3c Figure 1: Subnets in a Network%0a
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  45. host:1616857344=2a02:1205:34c1:94e0:1519:e2fd:b709:801e
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  46. author:1616857260=chewy
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  47. diff:1616857260:1616857228:=48c48%0a%3c Attach:IPV4/IPV4.gif%0a\ No newline at end of file%0a---%0a> %25width=210px rfloat%25 Attach:IPV4/IPV4.gif%0a\ No newline at end of file%0a
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  48. host:1616857260=2a02:1205:34c1:94e0:1519:e2fd:b709:801e
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  50. diff:1616857228:1616857204:=48c48%0a%3c %25width=210px rfloat%25 Attach:IPV4/IPV4.gif%0a\ No newline at end of file%0a---%0a> %25width=400px rfloat%25 Attach:IPV4/IPV4.gif%0a\ No newline at end of file%0a
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  53. diff:1616857204:1616856920:=48d47%0a%3c %25width=400px rfloat%25 Attach:IPV4/IPV4.gif%0a\ No newline at end of file%0a
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  54. host:1616857204=2a02:1205:34c1:94e0:1519:e2fd:b709:801e
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    56. 

  56. diff:1616856920:1616856725:=
    57. 

  57. host:1616856920=2a02:1205:34c1:94e0:1519:e2fd:b709:801e
    58. 

  58. author:1616856725=chewy
    59. 

  59. diff:1616856725:1616856560:=32,47d31%0a%3c %0a%3c In each IP address class, the number of host-number bits raised to the power of 2 indicates how many host numbers can be created for a particular network prefix. Class A addresses have 224 (or 16,777,216) possible host numbers, class B addresses have 216 (or 65,536) host numbers, and class C addresses have 28 (or 256) possible host numbers.%0a%3c %0a%3c !!IPv4 Dotted Decimal Notation%0a%3c %0a%3c The 32-bit IPv4 addresses are most often expressed in dotted decimal notation, in which each octet (or byte) is treated as a separate number. Within an octet, the rightmost bit represents 20 (or 1), increasing to the left until the first bit in the octet is 27 (or 128). Following are IP addresses in binary format and their dotted decimal equivalents:%0a%3c %0a%3c %25center%2511010000 01100010 11000000 10101010 = 208.98.192.170%0a%3c %0a%3c %25center%2501110110 00001111 11110000 01010101 = 118.15.240.85%0a%3c %0a%3c %25center%2500110011 11001100 00111100 00111011 = 51.204.60.59%0a%3c %0a%3c %0a%3c !!IPv4 Subnetting%0a%3c %0a
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  60. host:1616856725=2a02:1205:34c1:94e0:1519:e2fd:b709:801e
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    62. 

  62. diff:1616856560:1616856526:=23d22%0a%3c %0a25d23%0a%3c %0a
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  63. host:1616856560=2a02:1205:34c1:94e0:1519:e2fd:b709:801e
    64. 

  64. author:1616856526=chewy
    65. 

  65. diff:1616856526:1616855951:=22,29c22,27%0a%3c %25center%2500000000 xxxxxxxx xxxxxxxx xxxxxxxx (Class A)%0a%3c %25center%2500000000 00000000 xxxxxxxx xxxxxxxx (Class B)%0a%3c %25center%2500000000 00000000 00000000 xxxxxxxx (Class C)%0a%3c %0a%3c %0a%3c Because each bit (x) in a host number can have a 0 or 1 value, each represents a power of 2. For example, if only 3 bits are available for specifying the host number, only the following host numbers are possible:%0a%3c %0a%3c %25center%25111 110 101 100 011 010 001 000%0a---%0a>                                             00000000 xxxxxxxx xxxxxxxx xxxxxxxx (Class A)%0a>                                             00000000 00000000 xxxxxxxx xxxxxxxx (Class B)%0a>                                             00000000 00000000 00000000 xxxxxxxx (Class C)%0a> %0a> %0a> %0a
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  66. host:1616856526=2a02:1205:34c1:94e0:1519:e2fd:b709:801e
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  67. author:1616855951=chewy
    68. 

  68. diff:1616855951:1616855769:=2,26d1%0a%3c %0a%3c IPv4 addresses are 32-bit numbers that are typically displayed in dotted decimal notation. A 32-bit address contains two primary parts: the network prefix and the host number.%0a%3c %0a%3c All hosts within a single network share the same network address. Each host also has an address that uniquely identifies it. Depending on the scope of the network and the type of device, the address is either globally or locally unique. Devices that are visible to users outside the network (webservers, for example) must have a globally unique IP address. Devices that are visible only within the network must have locally unique IP addresses.%0a%3c %0a%3c IP addresses are assigned by a central numbering authority called the Internet Assigned Numbers Authority (IANA). IANA ensures that addresses are globally unique where needed and has a large address space reserved for use by devices not visible outside their own networks.%0a%3c %0a%3c !!IPv4 Classful Addressing%0a%3c %0a%3c To provide flexibility in the number of addresses distributed to networks of different sizes, 4-octet (32-bit) IP addresses were originally divided into three different categories or classes: class A, class B, and class C. Each address class specifies a different number of bits for its network prefix and host number:%0a%3c %0a%3c *    Class A addresses use only the first byte (octet) to specify the network prefix, leaving 3 bytes to define individual host numbers.%0a%3c %0a%3c *    Class B addresses use the first 2 bytes to specify the network prefix, leaving 2 bytes to define host addresses.%0a%3c %0a%3c *    Class C addresses use the first 3 bytes to specify the network prefix, leaving only the last byte to identify hosts.%0a%3c %0a%3c In binary format, with an x representing each bit in the host number, the three address classes can be represented as follows:%0a%3c %0a%3c %0a%3c                                             00000000 xxxxxxxx xxxxxxxx xxxxxxxx (Class A)%0a%3c                                             00000000 00000000 xxxxxxxx xxxxxxxx (Class B)%0a%3c                                             00000000 00000000 00000000 xxxxxxxx (Class C)%0a%3c %0a%3c %0a
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  69. host:1616855951=2a02:1205:34c1:94e0:1519:e2fd:b709:801e
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  70. author:1616855769=chewy
    71. 

  71. diff:1616855769:1616855744:=1c1%0a%3c !!Understanding IPv4 Addressing%0a---%0a> !!'+Understanding IPv4 Addressing+'%0a
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  72. host:1616855769=2a02:1205:34c1:94e0:1519:e2fd:b709:801e
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  73. author:1616855744=chewy
    74. 

  74. diff:1616855744:1616855744:=1,2d0%0a%3c !!'+Understanding IPv4 Addressing+'%0a%3c %0a
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  75. host:1616855744=2a02:1205:34c1:94e0:1519:e2fd:b709:801e
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