HOST PORTIONNETWORK PORTION The problem with subnetting A: 28 hosts B: 60 hosts C: 20 hostsD: 10 hosts E: 2 hosts Network: /24 The largest.

Presentación del tema: "HOST PORTIONNETWORK PORTION The problem with subnetting A: 28 hosts B: 60 hosts C: 20 hostsD: 10 hosts E: 2 hosts Network: /24 The largest."— Transcripción de la presentación:

1 HOST PORTIONNETWORK PORTION The problem with subnetting A: 28 hosts B: 60 hosts C: 20 hostsD: 10 hosts E: 2 hosts Network: 192.168.1.0 /24 The largest subnet: 60 hosts Bits required in host portion? 5 bits?2 5 -2 = 30 6 bits?2 6 -2 = 62 ✔ 192.168.1.0000 0000 2 bits for subnet portion How many subnets? 2 2 = 4 Not enough subnets! Subnets needed: 5 Bits required for subnet portion? 2 bits?2 2 = 4 3 bits?2 3 = 8 ✔ 5 bits are left for host portion How many hosts? 2 5 -2 = 30 The largest subnet won’t fit!

2 Subnetting is like slicing a pizza HOST PORTIONNETWORK PORTION 192.168.1.0000 0000 192.168.1.0000 0000 192.168.1.0/25 192.168.1.1000 0000 192.168.1.128/25 192.168.1.0000 0000 192.168.1.0/26 192.168.1.0100 0000 192.168.1.64/26 192.168.1.1000 0000 192.168.1.128/26 192.168.1.1100 0000 192.168.1.192/26 /25 /26 /24 192.168.1.1100 0000 192.168.1.192/28 192.168.1.1101 0000 192.168.1.208/28 192.168.1.1110 0000 192.168.1.224/28 192.168.1.1111 0000 192.168.1.240/28 HOST PORTIONNETWORK PORTION 192.168.1.1100 0000 /28 /26

3 E D C A B How to VLSM A: 28 hosts B: 60 hosts C: 20 hostsD: 10 hosts E: 2 hosts Network: 192.168.1.0 /24 192.168.1.0 192.168.1.255 0 255 128 127 /24 /25 /26 63 64 /27 96 95 /25 192 191 160 159 144 143 /28 152 151 148148 147147 /30 NetNet AddrSizePrefixSubnet MaskAssignable RangeBroadcast A 192.168.1.6430/27255.255.255.224192.168.1.65-192.168.1.94192.168.1.95 B 192.168.1.062/26255.255.255.192192.168.1.1-192.168.1.62192.168.1.63 C 192.168.1.9630/27255.255.255.224192.168.1.97-192.168.1.126192.168.1.127 D 192.168.1.12814/28255.255.255.240192.168.1.129-192.168.1.142192.168.1.143 E 192.168.1.1442/30255.255.255.252192.168.1.145-192.168.1.146192.168.1.147

4 In reality, VLSM is rarely used as this in corporate networks Address space gets packed and does not allow for easy future expansion Addresses for networks are difficult to memorize Configurations (routing, ACLs, DHCP) are harder to implement and maintain Unnecessary complexity, prone to errors Private address spaces are plentiful to create intuitive addressing schemes: 10.1.2.3 = 10. building number. floor number. host address 10.1.2.3 = 10. campus id. dept id. host address Understanding VLSM is still very useful to Be fluent with IPv4 address arithmetic Understand CIDR and summarization Note