Understanding IP Requirements• Subnetworks on the LAN/WAN need to be issued using perfect powers of 2• 22 = 4• 23 = 8• 24 = 16• 25 = 32• 26 = 64• 27 = 128
Scaling Subnets• With a requirement of 23 nodes…• The next perfect power of 2 that meets this need = 32• 25 = 32 5 host bits needed• Last Octet is then represented as: – A.B.C.NNNHHHHH N=Network H=Host – 11111111.11111111.11111111.11100000
VLSM and Routing Protocols• Does your routing protocol support varying the length of the subnet mask from one interface to another?• Can you re-subnet a subnet differently from one interface to another and still advertise that subnetwork via RIPv1, RIPv2, OSPF, EIGRP, ISIS, BGP?
Routing Protocols• Supporting VLSM – RIP version 2 – EIGRP – OSPF – ISIS• Not Supporting VLSM – IGRP – RIP version 1
Which Routing Protocols willadvertise all Networks correctly?
Non-VLSM capable RoutingProtocols will work just fine!
Problem!• The 192.168.20.0 /24 network gives us: – 1 Network – 254 Nodes Available for Assignment• 13 Subnetworks Required• Network Demands range from 4 – 32 nodes per LAN / WAN segment
Future Expansion Danger• Note the three locations with the and• If we need to add a network printer or visitor with laptop, the IP addressing scheme will have to be modified.• This results in downtime and careful migration planning There must be a better way!