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Lecture #2 VLSM

Lecture #2 VLSM. Asst.Prof. Dr.Anan Phonphoem Department of Computer Engineering, Faculty of Engineering, Kasetsart University, Bangkok, Thailand. Outline. VLSM. VLSM. Variable-length subnet mask Classful allows only one subnet in a network > one subnet in an autonomous system

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Lecture #2 VLSM

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  1. Lecture #2VLSM Asst.Prof. Dr.Anan Phonphoem Department of Computer Engineering, Faculty of Engineering, Kasetsart University, Bangkok, Thailand

  2. Outline • VLSM

  3. VLSM • Variable-length subnet mask • Classful allows only one subnet in a network • > one subnet in an autonomous system • Maximizing the use of address (Subnet Zero) • “Subnetting a Subnet” • Routing that support VLSM • OSPF, Integrated IS-IS, EIGRP, RIPv2, and static routing

  4. Subnet with VLSM 192.168.10.0/24

  5. Perth KL Subnet with VLSM • Select the biggest first • 192.168.10.0/24 • 192.168.10.0/26 • 192.168.10.64/26 • 192.168.10.128/26 • 192.168.10.192/26 • 192.168.10.64/26 • 192.168.10.64/27 • 192.168.10.96/27 • 192.168.10.128/27 • 192.168.10.192/27

  6. Sydney Singapore Perth – KL Sydney – KL Singapore – KL Subnet with VLSM • 192.168.10.96/27 • 192.168.10.96/28 • 192.168.10.112/28 • 192.168.10.224/28 • 192.168.10.240/28 • 192.168.10.224/28 • 192.168.10.128/30 • 192.168.10.132/30 • 192.168.10.136/30 • 192.168.10.140/30

  7. Subnet with VLSM

  8. Assignment 250 Stations 165.23.220.0/20 CPE IE EE 700 Stations 500 Stations 100 Stations

  9. Solution • 165.23.220.0/20 • 165.23.208.0/22 • 165.23.212.0/22 • 165.23.216.0/22 • 165.23.220.0/22 1022 Hosts • 165.23.212.0/22 • 165.23.212.0/23 • 165.23.214.0/23 510 Hosts • 165.23.214.0/23 • 165.23.214.0/24 • 165.23.215.0/24 254 Hosts 2 Hosts • 165.23.215.128/25 • 165.23.215.128/30 • 165.23.215.132/30 • 165.23.215.136/30 • … • 165.23.215.0/24 • 165.23.215.0/25 • 165.23.215.128/25 126 Hosts

  10. Solution 165.23.214.0/24 250 Stations 165.23.220.0/20 CPE 165.23.215.128/30 IE 165.23.215.132/30 EE 700 Stations 500 Stations 100 Stations 165.23.208.0/22 165.23.212.0/23 165.23.215.0/25

  11. Route Aggregation • Route summarization • Supernetting • Possible only if routers of a network use a classless routing protocol(OSPF or EIGRP) • Carry 32-bit IP address and bit mask in the routing updates • Share the same high-order bits

  12. Routing Protocols • Autonomous systems (AS) • generally administered by a single entity • Each AS has a routing technology which can differ from other autonomous systems • Interior Gateway Protocol (IGP) • Routing in the AS • Exterior Gateway Protocol (EGP) • transfer routing information between autonomous systems

  13. RIP • work as an IGP • in a moderate-sized AS • RIPv1 is classful IGP • distance vector protocol • Use hop count as a metric • Route update is 30 sec (Broadcast) • load balancing upto 6 paths

  14. RIPv2 • allows it to send out subnet mask information with the route update • provides for authentication in its updates • multicasts routing updates (224.0.0.9)

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