A Variable Length Subnetting Example

sumon_ahsan  Diamond  (1)
6 years 7 months ago  View: 1025  Reply: 3

Consider a corporation that was assigned a Class C network 165.214.32.0, and it has the requirement to split this address range into five separate networks. The required number of hosts for each subnet are following:

1. Subnet: 50 hosts

2. Subnet: 50 hosts

3. Subnet: 50 hosts

4. Subnet: 30 hosts

5. Subnet: 30 hosts

This cannot be achieved by using static subnetting. For this case, the static subnetting can only divide the network into four subnets with 64 hosts each or eight subnet with 32 hosts each. This method would not meet the requirement. To be able to divide the network into five subnets, multiple masks should be

defined. Using a mask of 255.255.255.192, the network will be divided into four subnets with 64 hosts each. After that, the last subnet can be further divided into two subnets with 32 hosts each by using a mask of 255.255.255.224. There will be three subnets with 64 hosts each and two subnets with 32 hosts each. This would meet the requirements.

Obtaining a Subnet Mask

Usually, hosts will store the subnet mask to be used in a configuration file. However, sometimes this cannot be done, as for example in the case of a diskless workstation. The ICMP protocol includes two messages, address mask request and address mask reply, that allow hosts to obtain the correct subnet mask from a

server. See 2.2.1.10, “Address Mask Request (17) and Address Mask Reply (18)” on page 65 for more information.

 

 

Geek Guy Subnet Mask Table

----------------------------------------------------------
Subnet Mask: 255.255.255.0 Hex Mask: 0xffffff00
Subnet Bits: 24 Host Bits: 8
Number of Subnets: 1 Hosts per Subnet: 254

Network Address IP Range Broadcast Address
.0 .1-.254 .255

----------------------------------------------------------
Subnet Mask: 255.255.255.128 Hex Mask: 0xffffff80
Subnet Bits: 25 Host Bits: 7
Number of Subnets: 2 Hosts per Subnet: 126

Network Address IP Range Broadcast Address
.0 .1-.126 .127
.128 .129-.254 .255

----------------------------------------------------------
Subnet Mask: 255.255.255.192 Hex Mask: 0xffffffc0
Subnet Bits: 26 Host Bits: 6
Number of Subnets: 4 Hosts per Subnet: 62

Network Address IP Range Broadcast Address
.0 .1-.62 .63
.64 .65-.126 .127
.128 .129-.190 .191
.192 .193-.254 .255

----------------------------------------------------------
Subnet Mask: 255.255.255.224 Hex Mask: 0xffffffe0
Subnet Bits: 27 Host Bits: 5
Number of Subnets: 8 Hosts per Subnet: 30

Network Address IP Range Broadcast Address
.0 .1-.30 .31
.32 .33-.62 .63
.64 .65-.94 .95
.96 .97-.126 .127
.128 .129-.158 .159
.160 .161-.190 .191
.192 .193-.222 .223
.224 .225-.254 .255

----------------------------------------------------------
Subnet Mask: 255.255.255.240 Hex Mask: 0xfffffff0
Subnet Bits: 28 Host Bits: 4
Number of Subnets: 16 Hosts per Subnet: 14

Network Address IP Range Broadcast Address
.0 .1-.14 .15
.16 .17-.30 .31
.32 .33-.46 .47
.48 .49-.62 .63
.64 .65-.78 .79
.80 .81-.94 .95
.96 .97-.110 .111
.112 .113-.126 .127
.128 .129-.142 .143
.144 .145-.158 .159
.160 .161-.174 .175
.176 .177-.190 .191
.192 .193-.206 .207
.208 .209-.222 .223
.224 .225-.238 .239
.240 .241-.254 .255

---------------------------------------------------------
Subnet Mask: 255.255.255.248 Hex Mask: 0xfffffff8
Subnet Bits: 29 Host Bits: 3
Number of Subnets: 32 Hosts per Subnet: 6

Network Address IP Range Broadcast Address
.0 .1-.6 .7
.8 .9-.14 .15
.16 .17-.22 .23
.24 .25-.30 .31
.32 .33-.38 .39
.40 .41-.46 .47
.48 .49-.54 .55
.56 .57-.62 .63
.64 .65-.70 .71
.72 .73-.78 .79
.80 .81-.86 .87
.88 .89-.94 .95
.96 .97-.102 .103
.104 .105-.110 .111
.112 .113-.118 .119
.120 .121-.126 .127
.128 .129-.134 .135
.136 .137-.142 .143
.144 .145-.150 .151
.152 .153-.158 .159
.160 .161-.166 .167
.168 .169-.174 .175
.176 .177-.182 .183
.184 .185-.190 .191
.192 .193-.198 .199
.200 .201-.206 .207
.208 .209-.214 .215
.216 .217-.222 .223
.224 .225-.230 .231
.232 .233-.238 .239
.240 .241-.246 .247
.248 .249-.254 .255

---------------------------------------------------------
Subnet Mask: 255.255.255.252 Hex Mask: 0xfffffffc
Subnet Bits: 30 Host Bits: 2
Number of Subnets: 64 Hosts per Subnet: 2

Network Address IP Range Broadcast Address
.0 .1-.2 .3
.4 .5-.6 .7
.8 .9-.10 .11
.12 .13-.14 .15
.16 .17-.18 .19
.20 .21-.22 .23
.24 .25-.26 .27
.28 .29-.30 .31
.32 .33-.34 .35
.36 .37-.38 .39
.40 .41-.42 .43
.44 .45-.46 .47
.48 .49-.50 .51
.52 .53-.54 .55
.56 .57-.58 .59
.60 .61-.62 .63
.64 .65-.66 .67
.68 .69-.70 .71
.72 .73-.74 .75
.76 .77-.78 .79
.80 .81-.82 .83
.84 .85-.86 .87
.88 .89-.90 .91
.92 .93-.94 .95
.96 .97-.98 .99
.100 .101-.102 .103
.104 .105-.106 .107
.108 .109-.110 .111
.112 .113-.114 .115
.116 .117-.118 .119
.120 .121-.122 .123
.124 .125-.126 .127
.128 .129-.130 .131
.132 .133-.134 .135
.136 .137-.138 .139
.140 .141-.142 .143
.144 .145-.146 .147
.148 .149-.150 .151
.152 .153-.154 .155
.156 .157-.158 .159
.160 .161-.162 .163
.164 .165-.166 .167
.168 .169-.170 .171
.172 .173-.174 .175
.176 .177-.178 .179
.180 .181-.182 .183
.184 .185-.186 .187
.188 .189-.190 .191
.192 .193-.194 .195
.196 .197-.198 .199
.200 .201-.202 .203
.204 .205-.206 .207
.208 .209-.210 .211
.212 .213-.214 .215
.216 .217-.218 .219
.220 .221-.222 .223
.224 .225-.226 .227
.228 .229-.230 .231
.232 .233-.234 .235
.236 .237-.238 .239
.240 .241-.242 .243
.244 .245-.246 .247
.248 .249-.250 .251
.252 .253-.254 .255

----------------------------------------------------------
Subnet Mask: 255.255.255.255 Hex Mask: 0xffffffff
Subnet Bits: 32 Host Bits: 0
Number of Subnets: 255 Hosts per Subnet: 1

TISLAM  Platinum 
6 years 7 months ago
very details info...
TISLAM  Platinum 
6 years 7 months ago
what is ICMP ?
gokibria  Diamond 
6 years 7 months ago
very good share...