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IP Addressing, Multicasting, and IPv6 • Chapter 4 307 To improve readability, the 32-bit IP address splits into four blocks of 8 bits like this: 00001010 00001011 00001100 00001101 Finally, each 8-bit block is converted to decimal and the decimal values are separated with periods or “dots.”The converted IPv4 address, expressed as a dotted decimal address, is: 10.11.12.13 It is much easier to remember an IP address of 10.11.12.13 than to remember a string of bits such as 00001010000010110000110000001101. IP addresses and their values and uses are dis- cussed in detail later in this chapter. All information transported over IP is carried in IP packets with the format shown in Figure 4.2.The header length can vary somewhat depending on whether the options field is present and the number of bits that are used to specify these options.This variation in length adds to the pro- cessing burden, as predictability and consistency are not achieved. ■ Version 4-bit field. Identifies the version of the IP (4 or 6). Makes IPv6 backward- compatible with IPv4. ■ Header Length 4-bit field. Indicates the length of the header, as the IPv4 header is a variable between 20 and 64 bytes. ■ Type of Service (ToS) Identifies the priority of packet. www.syngress.com Figure 4.2 The IPv4 Header Version Fragment Offset Flags Identification Total Length Type of Service Header Length Time to Live Data Options Destination Address Source Address Header Checksum Protocol 4 4 8 16 16 3 13 8 8 16 32 32 0 - 40 variable bits 253_BDCisco_04.qxd 10/14/03 10:05 AM Page 307 308 Chapter 4 • IP Addressing, Multicasting, and IPv6 ■ Total Length The entire length of the IP portion of the packet. Called payload length in IPv6. ■ Identification, Flags, Fragment Offset Handles the fragmentation and reassembly of packets. Not necessary in the IPv6 header as they are handled by the source. ■ Time To Live (TTL) Limits the number of hops the packet is allowed to transit. At each hop, a router decrements this field, and when it reaches zero, the packet is removed from the network. ■ Protocol Indicates the next protocol (header) following the IPv4 header, such as TCP or User Datagram Protocol (UDP). ■ Header Checksum Maintains the integrity of the IPv4 header. ■ Source and Destination Address 32-bit addresses that identify the source and desti- nation for this packet. ■ Options If enabled, each intermediate node in the path needs to examine it, which can cause inefficient router performance. Familiarity with the IP address classes, masks, and structure are essential to mastering and using IP.The most fundamental aspect of IP is its addresses. Classful Addressing - Structure and Size of Each Type IPv4 addressing assigns a logical address to a physical device. While physical addresses are suffi- cient for communicating while on the same network, more is necessary for communicating with devices on other networks.The role of a network address such as IP is to address and route traffic between networks. A 32-bit address is large enough to provide 4,294,967,296 individual addresses. Since all net- works are not the same size, the addresses are grouped together for administrative purposes into address classes to ease allocation and control. IP Address Classes There are five classes of IP addresses. Only three classes are used to assign unicast addresses to end devices such as routers, workstations, servers, and so on.Table 4.1 shows IP address classes and their starting and ending addresses.The “n’s” represent the network number bits in the address, and the “h’s” are the locally administered portions of the address. Table 4.1 IP Address Classes Starting Class Format Address Ending Address A 0nnnnnnn hhhhhhhh hhhhhhhh hhhhhhhh 1.0.0.0 127.255.255 255 B 10nnnnnn nnnnnnnn hhhhhhhh hhhhhhhh 128.0.0.0 191.255.255.255 C 110nnnnn nnnnnnnn nnnnnnnn hhhhhhhh 192.0.0.0 233.255.255.255 www.syngress.com Continued 253_BDCisco_04.qxd 10/14/03 10:05 AM Page 308 IP Addressing, Multicasting, and IPv6 • Chapter 4 309 Table 4.1 IP Address Classes Starting Class Format Address Ending Address D 1110mmmm mmmmmmmm 224.0.0.0 239.255.255.255 mmmmmmmm mmmmmmmm E 1111rrrr rrrrrrr rrrrrrrr rrrrrrrr 240.0.0.0 255.255.255.255 Class A Class A is the largest grouping of addresses.The first 8 bits indicate the network number.The remaining 24 bits can be modified to represent addresses assigned to “local” devices. The first bit of a Class A network address is always a zero, which means network numbers begin at 1 and end at 127. Class A IP addresses range from 1.0.0.0 to 127.255.255.255. With a 24-bit locally administered address space, the total number of addresses in a Class A network is 16,777,216.The default mask for Class A addresses is 255.0.0.0. Class B The first bits are always 10 in a Class B address.The first 16 bits of a Class B address indicate the network number.The remaining 16 bits represent addresses assigned to “local” hosts. Class B net- work numbers begin at 128 and end at 191, which is an effective address range of 128.0.0.0 to 191.255.255.255. The first two dotted decimal numbers are included in the network number because the net- work number in a Class B address is 16 bits long.The 16-bit locally administered address space allows each Class B network to contain 65,536 addresses.The number of Class B networks avail- able for administration is 16,384.The default mask for Class B addresses is 255.255.0.0. Class C The first 24 bits of a Class C address are the network number, leaving 8 host bits.A Class C address is identified by the “110” in the first 3 bits. Class C network numbers begin at 192 and end at 223, creating IP addresses from 192.0.0.0 and 223.255.255.255.The 8-bit locally adminis- tered address space allows each Class C network to contain 256 addresses.The number of Class C networks available for administration is 2,097,152.The default mask associated with Class C addresses is 255.255.255.0. Class D Class D addresses, ranging from 224.0.0.0 to 239.255.255.255, are used for multicast applications. Unlike broadcasts which are directed to all devices on a network or a unicast address which is destined for a single device, multicast addresses are targeted to a group of devices that run some type of service (such as Open Shortest Path First [OSPF]) or group application (such as video), where the same data needs to go to multiple devices, but not all devices, on a particular network. www.syngress.com 253_BDCisco_04.qxd 10/14/03 10:05 AM Page 309 310 Chapter 4 • IP Addressing, Multicasting, and IPv6 Class E Class E addresses (240.0.0.0 to 255.255.255.255) are “reserved” for special experimental purposes. The only use of Class E addresses to date is the all hosts broadcast, 255.255.255.255. Class A, B, and C addresses include default masks. It is advantageous to use only the amount of addresses necessary to cover a particular network. For example, it would be wasteful to allocate 500 IP addresses to a network that will never contain more than 12 addressable devices. Various strategies have been developed to more effectively handle IP addresses, including subnetting. Strategies to Conserve Addresses Several strategies have been developed and implemented to help the Internet community cope with the exhaustion of IP addresses.These strategies help reduce the load on Internet routers and also help administrators use globally unique IP addresses more efficiently.The following three strategies were mentioned in previous sections, and are discussed in more detail in the following paragraphs: ■ Classless Inter-Domain Routing (CIDR) ■ Variable-Length Subnet Mask (VLSM) ■ Private Addressing CIDR CIDR (RFCs 1517, 1518, and 1519) reduces route table sizes as well as IP address waste. Instead of full Class A, B, or C addresses, organizations can be allocated subnet blocks. For example, if a network needed 3,000 addresses, a single Class C network (256 addresses) would be insufficient. However, if a Class B network were assigned (65,536 addresses), 62,000 addresses would be wasted. With CIDR, a block of 4,096 addresses can be allocated—the equivalence of 16 Class C networks.This block of addresses covers the immediate addressing needs, allows room for growth, and uses global addresses efficiently. VLSM VLSM conserves IP addresses by tailoring the mask to each subnet. Subnet masks are appropri- ated to meet the amount of addresses required.The idea is to assign “just the right amount” of addresses to each subnet. Many organizations have point-to-point wide area network (WAN) links. Normally, these links comprise a subnet with only the 2 addresses required. By using a routing protocol that supports VLSM, administrator’s can use a block of addresses much more efficiently. Private Addresses The most effective strategy for conserving globally unique (public) IP addresses is not using any. If an enterprise network is using TCP/IP protocols but is not communicating with hosts in the global Internet, public IP addresses are not needed. If the internetwork is limited to one organi- www.syngress.com 253_BDCisco_04.qxd 10/14/03 10:05 AM Page 310 IP Addressing, Multicasting, and IPv6 • Chapter 4 311 zation, the IP addresses need only be unique within that organization. Only networks that inter- face with public networks such as the Internet need public addresses. Using public addresses on the outside and private addresses for inside networks is very effective. Network Address Translation (NAT) is used to convert those private (inside) addresses to public (outside) addresses. Public versus Private Address Spaces The IP requires that each interface on a network have a unique address. If the scope of a network is global, the addresses must be globally unique. Since global uniqueness must be assured, a cen- tralized authority must be responsible for making sure IP address assignments are made correctly and fairly. To meet the demands of a growing Internet community, the Internet Assigned Numbers Authority (IANA) was replaced by the Internet Corporation for Assigned Names and Numbers (ICANN). If an organization wants to use IP protocols and applications in its network, but is not connecting its network to the global Internet, the IP addresses it uses do not need to be globally unique. A network of this type is called a “private network,” and the addresses used are called “private addresses.” RFC 1918 - Private Network Addresses RFC1918 conserves globally unique IP addresses by providing three blocks of addresses that are never officially allocated to any organization.These blocks can then be used in private networks without fear of duplicating any officially assigned IP addresses in other organizations. The Three Address Blocks RFC1918 designates three ranges of IP addresses as private: ■ 10.0.0.0 through 10.255.255.255 ■ 172.16.0.0 through .31.255.255 ■ 192.168.0.0 through 192.168.255.255 Table 4.2 summarizes the private address blocks defined by RFC1918. Notice the CIDR shorthand for the mask. Table 4.2 Private IP Address Blocks Number of Address Block Classful Equivalent Prefix Length Addresses 10.0.0.0–10.255.255.255 1 Class A /8 16,777,216 256 Class B 65,536 Class C 172.16.0.0–172.31.255.255 16 Class B /12 1,048,576 4,096 Class C 192.168.0.0–192.168.255.255 1 Class B /16 65,536 256 Class C www.syngress.com 253_BDCisco_04.qxd 10/14/03 10:05 AM Page 311 312 Chapter 4 • IP Addressing, Multicasting, and IPv6 Considerations The address blocks in Table 4.2 can be used in any network at any time. However, devices using these addresses will not be able to communicate with other hosts on the Internet without some kind of address translation. Some benefits of using private addresses are: ■ Number of Addresses There are plenty of addresses for most internal networking needs. ■ Security Private addresses are not routable on the Internet.The translation from pri- vate to public addresses further obscures internal network information. ■ Renumbering If using NAT, no readdressing of privately addressed networks is neces- sary in order to access public networks. ■ Networks Treating private addresses as public addresses when allocating ensures that efficiency and design are maximized. The Fundamentals of Subnetting Subnetting allows administrators to apportion IP addresses for more efficient use. For example, if an administrator has a Class B address and they assign it “as is” to a network of 10 devices, the waste of address space is incredible. However, if that address is divided so that only 10 addresses are used from it, an administrator can address a small network and retain the remaining addresses for their other networks.The process of using a subnet mask is described in RFC950. What the Mask Does Masks (which are 32 bits) indicate the range of addresses in use on a particular network. Masks identify the network, subnet, and host bits in an address.The subnet mask is used to interpret addresses to determine how they are subnetted. Assume that 172.31.0.0 is a Class B network address, which means that the first 16 bits of the address are the network number. Using the mask assigned to this network, it can be determined that a certain device is on the 172.31.240.0 subnet. Each class has a “default” or natural mask associated with it. Class A 255.0.0.0 Class B 255.255.0.0 Class C 255.255.255.0 The default or “natural mask” for the Class A address is 255.0.0.0. In this case, the mask indi- cates that the first 8 bits represent the network number and must be used when evaluating a Class A address for subnetting. If a device has a Class A address assigned with the natural mask 255.0.0.0, there is no subnetting in that network. If a device has a Class A address and a mask that is not 255.0.0.0, the network has been subnetted and the device is in a subnet of the Class A network. www.syngress.com 253_BDCisco_04.qxd 10/14/03 10:05 AM Page 312 IP Addressing, Multicasting, and IPv6 • Chapter 4 313 Subnet Mask Components A mask is a 32-bit binary number that is expressed in dotted decimal notation. By default, a mask contains two fields, the network field and the host field.These correspond to the network number and the locally administered part of the network address. When an administrator subnets, they are adjusting the way they view the IP address. In the following example, the network is indicated by the first two 255 entries (16 bits) and the host field is indicated by the ending 0.0 (last 16 bits). 172.31.88.250 255.255.0.0 The network number is 172.31 and the host number is 88.250. In other words, the first 16 bits are the network number and the remaining 16 bits are the host number. Subnetting converts the address hierarchy from the network and the host to the network, subnet and host. Subnetting the 172.31.0.0 network with a mask of 255.255.255.0 adds more information: the subnet bits. As with the previous example, the 172.31 is still the network number. With a mask of 255.255.255.0, the third octet is used to indicate where the subnet number is located.The subnet number is .88 and, finally, the host number is 250. 255.255.255.0 for a Class B network 255 255 255 0 11111111 11111111 11111111 00000000 Network Network Subnet Host The locally administered portion of the network address can be subdivided into subnetworks using the mask to identify the subnet bits. A certain number of bits are allocated to the subnet field and the remainder becomes the new host field. Binary Determination of Mask Values The first task in subnetting is determining how many networks containing how many hosts per network are needed.This information helps administrators divide and assign addresses efficiently. Addressing should be settled in the design phase; however, it can be done on any network that needs address optimization. Once this is complete, the next task is determining the right address and mask combinations that will achieve the addressing goals. Decimal Equivalent Mask Values Tables 4.3, 4.4, and 4.5 show the possible subnet masks that can be used in Class A, Class B, and Class C networks.These tables are useful for quickly determining the amount of hosts per subnet that would be achieved with a particular mask. www.syngress.com 253_BDCisco_04.qxd 10/14/03 10:05 AM Page 313 314 Chapter 4 • IP Addressing, Multicasting, and IPv6 Table 4.3 Class A Subnet Table Subnets Hosts Mask Subnet Bits Host Bits 2 8,388,606 255.128.0.0 1 23 4 4,194,302 255.192.0.0 2 22 8 2,097,150 255.224.0.0 3 21 16 1,048,574 255.240.0.0 4 20 32 524,286 255.248.0.0 5 19 64 262,142 255.252.0.0 6 18 128 131,070 255.254.0.0 7 17 256 65,534 255.255.0.0 8 16 512 32,766 255.255.128.0 9 15 1,024 16,382 255.255.192.0 10 14 2,048 8,190 255.255.224.0 11 13 4,096 4,094 255.255.240.0 12 12 8,192 2,046 255.255.248.0 13 11 16,384 1,022 255.255.252.0 14 10 32,768 510 255.255.254.0 15 9 65,536 254 255.255.255.0 16 8 131,072 126 255.255.255.128 17 7 262,144 62 255.255.255.192 18 6 524,288 30 255.255.255.224 19 5 1,048,576 14 255.255.255.240 20 4 2,097,152 6 255.255.255.248 21 3 4,194,304 2 255.255.255.252 22 2 Table 4.4 Class B Subnet Table Subnets Hosts Mask Subnet Bits Host Bits 2 32,766 255.255.128.0 1 15 4 16,382 255.255.192.0 2 14 8 8,190 255.255.224.0 3 13 16 4,094 255.255.240.0 4 12 32 2,046 255.255.248.0 5 11 64 1,022 255.255.252.0 6 10 128 510 255.255.254.0 7 9 256 254 255.255.255.0 8 8 512 126 255.255.255.128 9 7 1,024 62 255.255.255.192 10 6 www.syngress.com Continued 253_BDCisco_04.qxd 10/14/03 10:05 AM Page 314 IP Addressing, Multicasting, and IPv6 • Chapter 4 315 Table 4.4 Class B Subnet Table Subnets Hosts Mask Subnet Bits Host Bits 2,048 30 255.255.255.224 11 5 4,096 14 255.255.255.240 12 4 8,192 6 255.255.255.248 13 3 16,384 2 255.255.255.252 14 2 Table 4.5 Class C Subnet Table Subnets Hosts Mask Subnet Bits Host Bits 2 126 255.255.255.128 1 7 4 62 255.255.255.192 2 6 8 30 255.255.255.224 3 5 16 14 255.255.255.240 4 4 32 6 255.255.255.248 5 3 64 2 255.255.255.252 6 2 These subnet mask tables make it easier to determine which subnet mask to use for any given situation.As the table shows, the number of subnets increases and the number of hosts in each subnet decreases.As the number of subnet bits increases, the number of host bits decreases. Since there are a fixed number of bits to work with in each class of network address, each bit can be used in only one way as specified by the mask. Each bit must be either a subnet bit or a host bit. An increase in the number of subnet bits causes a reduction in the number of host bits, and vice versa. These tables assume that an administrator has been allocated their initial addresses with respect to the natural masks for the class of the address. For example, 192.168.1.0 would be allocated with a mask of 255.255.255.0 because it is a Class C address. However, it is possible to be allocated a range of addresses that exceed the boundaries of the class. For example, 192.160.0.0 with a mask of 255.255.0.0 provides an administrator with a Class C address with a Class B amount of addresses. In that case, the administrator would have 16 host bits to subnet that they would not normally have. This concept is called “classless addressing,” and is revisited later in this chapter. Addresses and Mask Interaction An IP address identifies a device on a network. IP addresses are assigned from classes that contain different groups of addresses. Each IP network has a network number. Each IP subnet has the network number of its parent network and a subnet number.The subnet number can be found by locating the subnet field in the subnet mask. If an administrator has an IP address of 172.31.8.0 with a mask of 255.255.255.0, they know that they have an address in the 172.31.8.0 network.The mask of 255.255.255.0 for this Class B address states that the first two octets (172.31) are network numbers; the third octet (8) is the subnet number, and the fourth octet is for host addresses. www.syngress.com 253_BDCisco_04.qxd 10/14/03 10:05 AM Page 315 316 Chapter 4 • IP Addressing, Multicasting, and IPv6 The address and mask combination can be expressed as 172.31.8.0 255.255.255.0 or as 172.31.8.0/24.The latter is classless addressing shorthand, called “prefix-length,” which identifies the total number of network and subnet bits used with this address. In our example, the first three octets are used for this purpose, which gives a total of 24 bits so used. When working with subnet masks in a professional environment, the prefix-length format is more common and easier to use.The network 172.31.8.0/24 would read 172 dot 31 dot 8 dot 0 slash 24. For consistency and learning purposes, we will continue to use the longhand format of expressing masks. In a Class B network, the first 16 bits are the network number. If devices have identical first 16 bits, they are in the same network with a Class B address. When the source network (172.31.8.0) shown here wants to communicate with the destination network (172.31.9.0), the first thing that needs to be determined is if they are on the same network. Source 172.31.8.0 10101010 00011111 00001000 00000000 Destination 172.31.9.0 10101010 00011111 00001001 00000000 This determination is made by what mask is associated with these networks. If the natural mask for Class B is used (255.255.0.0), they are on the same network—the first 16 bits match, putting them on the 172.31.0.0 network. However, if they were subnetted and are using a mask such as 255.255.255.0, then these would be two separate networks, in which case, a router is needed in order for the two networks to communicate. The following example shows how the masks make this distinction.This is a logical mathe- matical process using a logical AND process.This AND process states that a 1 and 1 equal 1, and any other combinations (0 and 0 and 1 and 0) equal 0.This enables us to determine the true net- work/subnet numbers. If using the natural mask for Class B (255.255.0.0), then both of these addresses are on the same network range. Source 172.31.8.0 10101010 00011111 00001000 00000000 AND 255.255.0.0 11111111 11111111 00000000 00000000 RESULT 172.31.0.0 10101010 00011111 00000000 00000000 Destination 172.31.9.0 10101010 00011111 00001001 00000000 AND 255.255.0.0 11111111 11111111 00000000 00000000 RESULT 172.31.0.0 10101010 00011111 00000000 00000000 NOTE The previous operation shows that 172.31.8.0 and 172.31.9.0 are both on the 172.31.0.0 network. www.syngress.com 253_BDCisco_04.qxd 10/14/03 10:05 AM Page 316 [...]... to devices .The following process shows how to derive the subnet number and broadcast address .The address of the device is 172.31.9.2 and the subnet mask is 255.255.255.2 24 1 Convert the locally administered portion of the address to binary (in this case, the fourth octet [2]) 00000010 2 Convert the locally administered portion of the mask to binary (in this case, the fourth octet [2 24] in the mask)... leaves the last octets to subnet and modify as needed We need a minimum of seven subnets 1 The subnet bit values (from right to left) for the last two octets are: 32768 163 84 8192 40 96 2 048 10 24 512 256 128 64 32 16 8 4 2 1 2 Turn on the bits that will give you seven subnets 0 0 0 0 0 0 0.0 0 0 0 0 0 0 0 1 1 1 = 7 3 Flip the bits: 1 1 1 0 0 0 0 0 0 0 0 0 0 4 Flipping turns the last two octets into: 2 24. 0... mapped to the Ethernet address Mapping the remaining 23 bits of 2 24. 8.168.8 is illustrated in Figure 4. 9 www.syngress.com 253_BDCisco_ 04. qxd 336 10/ 14/ 03 10:05 AM Page 336 Chapter 4 • IP Addressing, Multicasting, and IPv6 Figure 4. 9 Ethernet to IP Addressing for 2 24. 136.168.8 Octet First IP Address Second Binary 0000 0001 Ethernet Address 01 0000 0000 1101 1110 00 5E Fourth (128 + 8) 136 2 24 Third 168... need two addresses for each router interface on the link .The process is somewhat similar to what was used previously www.syngress.com 253_BDCisco_ 04. qxd 10/ 14/ 03 10:05 AM Page 323 IP Addressing, Multicasting, and IPv6 • Chapter 4 323 Recall the address 172.31.0.0 255.255. 244 .0; the first two octets plus the first 3 bits of the third octet cannot be subnetted; they are fixed and assigned as per our previous... subnet bits in the last five bits of the fourth octet are: 32 16 8 4 2 1 2 Turn on the bits that would give us 60 addresses (the following gives us 31 addresses total, subtract 1 for the broadcast, which leaves us with 30, which is what we want): 0 0 0 1 1 1 1 1 = 31 www.syngress.com 253_BDCisco_ 04. qxd 3 24 10/ 14/ 03 10:05 AM Page 3 24 Chapter 4 • IP Addressing, Multicasting, and IPv6 3 Invert the bits: 1... address format for consistency and clarity.This is the Ethernet multicast address for 2 24. 2.99.2 54 01:00:5E:02:63:FE One indirect lesson that can be gleaned during this process is that because the first 9 bits of the IP multicast address are ignored, the resulting Ethernet multicast address is not unique to 225.2.99.2 54 226.2.99.2 54, 227.2.99.2 54, and 2 24. 2.99.2 54 would all be mapped to 01:00:5E:02:63:FE As... 255.255.255. 248 Bit Values in a Octet: 128 64 32 16 8 4 2 1 Only the fourth octet in the mask ( 248 ) is important to our calculations Convert 248 to binary 11111000 .The value of the last bit, 8, is the lowest incrementing value that is used to derive the addresses in this range Start with 0, add 8 to derive the next IP network, add 8 to that, and so on until you reach 256, which is invalid, meaning the one... www.syngress.com 253_BDCisco_ 04. qxd 10/ 14/ 03 10:05 AM Page 337 IP Addressing, Multicasting, and IPv6 • Chapter 4 337 The multicast router manages the various multicast groups and handles the membership queries and reports and any other IGMP messages When a host joins a multicast group, the router interface to the network of that host will receive the multicast traffic .The host simply lets the router know to... where the diameter (span) of a multicast session is controlled by manipulating the Time-to-live (TTL) field Using TTL = 1 tells the IP router not to forward this packet to another network, since each router must decrement the TTL field by 1; if the TTL = 0, the packet is not forwarded The scoping of multicast addresses is based on the TTL value of the IP packet and controlled by the source Scoping using the. .. was adopted, wherein the lower 23 bits of the multicast IP address are incorporated as the lower 23 bits of the Media Access Control (MAC) address There are several requisites for the mapping process: 1 The first 4 high-order bits of the multicast IP address are reserved for Class D addressing and not mapped 2 The next 5 bits are not mapped and ignored 3 Only the 23 low order bits of the multicast IP address . 255.255.255.128 17 7 262, 144 62 255.255.255.192 18 6 5 24, 288 30 255.255.255.2 24 19 5 1, 048 ,576 14 255.255.255. 240 20 4 2,097,152 6 255.255.255. 248 21 3 4, 1 94, 3 04 2 255.255.255.252 22 2 Table 4. 4 Class B Subnet. 255.255.128.0 1 15 4 16,382 255.255.192.0 2 14 8 8,190 255.255.2 24. 0 3 13 16 4, 0 94 255.255. 240 .0 4 12 32 2, 046 255.255. 248 .0 5 11 64 1,022 255.255.252.0 6 10 128 510 255.255.2 54. 0 7 9 256 2 54 255.255.255.0. 14 2, 048 8,190 255.255.2 24. 0 11 13 4, 096 4, 0 94 255.255. 240 .0 12 12 8,192 2, 046 255.255. 248 .0 13 11 16,3 84 1,022 255.255.252.0 14 10 32,768 510 255.255.2 54. 0 15 9 65,536 2 54 255.255.255.0 16 8 131,072