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networking:tcpip:subnetting-case [2018/12/31 14:11]
networking:tcpip:subnetting-case [2018/12/31 14:11] (huidige)
Regel 1: Regel 1:
 +====== IP Subnetting Case ======
 +
 +===== Case =====
 +
 +Imagine an organization geographically divided into three locations:
 +
 +  * Location **A**: **120** ip-addresses needed
 +  * Location **B**: **40** ip-addresses needed
 +  * Location **C**: **32** ip-addresses needed
 +
 +All systems in your organization need direct Internet access.\\ ​ (no proxy, no NAT (Network Address Translation))
 +
 +  - What network class do you need from your ISP?​\\ ​ (ISP: Internet Service Provider)
 +  - Configure your network given the ip-range provided to you by the ISP.
 +
 +===== Solution =====
 +
 +===== 1. What network class do we need from the ISP? =====
 +
 +==== 1.1 Determine the number of hostbits needed in each network. ====
 +
 +^ Location ^ Formula ^ Hostbits ^ Max. Hosts ^
 +| A | 2<​sup>​h</​sup>​ -2 >= 120 | 7 | 126 |
 +| B | 2<​sup>​h</​sup>​ -2 >= 40 | 6 | 62 |
 +| C | 2<​sup>​h</​sup>​ -2 >= 32 | 6 | 62 |
 +
 +==== 1.2 Aggregate the subnets ====
 +
 +Aggregated subnets show up as one larger network to the outside world!
 +
 +**n**: Network bit\\ **h**: Host bit
 +
 +^ Location ^ Hostbits ^ Network ^
 +| B | 6 | A . B . C . **nn**hh_hhhh |
 +| C | 6 | A . B . C . **nn**hh_hhhh |
 +| B+C | 7 | A . B . C . **n**hhh_hhhh |
 +
 +^ Location ^ Hostbits ^ Network ^
 +| A | 7 | A . B . C . **n**hhh_hhhh |
 +| B+C | 7 | A . B . C . **n**hhh_hhhh |
 +| A+B+C | 8 | A . B . C . hhhh_hhhh |
 +
 +**Conclusion:​ We need a C-class ip-network: A . B . C . 0 /24**
 +
 +**Note:​**\\ ​ According to the rules subnets of all zeros or all ones are not allowed.\\ ​ So, when splitting a network into two subnets you actually have to split the network using **two** subnet bits, creating subnets: "​01",​ "​10"​.\\ ​ The big drawback is the waste of ip address space. Since subnets "​00"​and "​11"​ are illegal, you have to throw away half of the address space! Many organizations can't last such a waste.
 +
 +===== 2. Configure the Network =====
 +
 +The ISP gracefully provided us: **195 . 72 . 17 . 0 /24**
 +
 +^ Location A ^^^
 +^ Decimal ^ Last Octet ^ Item ^
 +| 255 . 255 . 255 . 128 | **1**000_0000 | Netmask |
 +| 195 . 72 . 17 . 0 | **0**000_0000 | Network |
 +| 195 . 72 . 17 . 1 | **0**000_0001 | First Host |
 +| 195 . 72 . 17 . 126 | **0**111_1110 | Last Host |
 +| 195 . 72 . 17 . 127 | **0**111_1111 | Broadcast |
 +
 +^ Location B ^^^
 +^ Decimal ^ Last Octet ^ Item ^
 +| 255 . 255 . 255 . 192 | **11**00_0000 | Netmask |
 +| 195 . 72 . 17 . 128 | **10**00_0000 | Network |
 +| 195 . 72 . 17 . 129 | **10**00_0001 | First Host |
 +| 195 . 72 . 17 . 190 | **10**11_1110 | Last Host |
 +| 195 . 72 . 17 . 191 | **10**11_1111 | Broadcast |
 +
 +^ Location C ^^^
 +^ Decimal ^ Last Octet ^ Item ^
 +| 255 . 255 . 255 . 192 | **11**00_0000 | Netmask |
 +| 195 . 72 . 17 . 192 | **11**00_0000 | Network |
 +| 195 . 72 . 17 . 193 | **11**00_0001 | First Host |
 +| 195 . 72 . 17 . 254 | **11**11_1110 | Last Host |
 +| 195 . 72 . 17 . 255 | **11**11_1111 | Broadcast |
 +
 +
 +====== . ======
 +Copyright(c) 2005 Integrated Services; Tux4u.nl\\
 +Author: ing. J.M. Waldorp; subnetting-case 2005-02-14
 +
  
networking/tcpip/subnetting-case.txt ยท Laatst gewijzigd: 2018/12/31 14:11 (Externe bewerking)