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IP Address

IP Address. Computer Network System Sirak Kaewjamnong. Three Level of Address. Host name ratree.psu.ac.th Internet IP address 192.168.100.3 (32 bits address with “ dot-decimal ” notation)

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IP Address

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  1. IP Address Computer Network System Sirak Kaewjamnong

  2. Three Level of Address • Host name • ratree.psu.ac.th • Internet IP address • 192.168.100.3 (32 bits address with “dot-decimal” notation) • Station address : Hardware address assigned to network interface card, refer to MAC address or Ethernet Address (48 bits) • 00:5c:f0:3b:00:4a

  3. cs05.cs.psu.ac.th 172.28.80.96 00:50:ba:49:9d:b9 Resolve IP address by Domain Name System(DNS) Resolve MAC address by Address Resolution Protocol(ARP) Converting Host Name to MAC Address

  4. IP address associated with interface (not machine) Each interface has its own IP address Machine with more than one interface called multi-home Router is multi-homed machine Multi-homed not to be router IP Address with Router 172.28.80.15 172.28.80.16 172.28.85.116 172.28.85.120 172.28.85.1 172.28.80.1 192.168.99.39 Internet 192.168.98.11 192.168.100.4 192.168.100.3 192.168.100.1

  5. Addressing Concept • Partitions address into 2 fields • network address • node address

  6. 32 bits 8,16,24 bits Network Host 32 bits 8 bits 8 bits 8 bits 8 bits . . . 172 28 80 96 10101100 00011100 01010000 01100000 IP Address

  7. 8 16 24 32 Class A 0 Network ID Host ID Class B 10 Network ID Host ID Class C 110 Network ID Host ID Class D 1110 Multicast Address Class E 11110 Unused IP Address Class 32 bits address length, contain 2 parts • Network identifier • Host identifier

  8. IP Address Class A 0 7 24 0.0.0.0 -127.255.255.255 224 16,677,214 B 10 14 16 128.0.0.0 -191.255.255.255 216 65,534 C 110 21 8 192.0.0.0 -223.255.255.255 28 254 D 1110 28 - 224.0.0.0-239.255.255.255 E 11110 27 - 240.0.0.0-247.255.255.255 Initial bits Bit net range address spaces Class Bit host usable

  9. Special Address • Host ID “all 0s” is reserved to refer to network number • 192.168.100.0, 158.108.0.0, 18.0.0.0 • Host ID “all 1s” is reserved to broadcast to all hosts on a specific network • 192.168.100.255, 158.108.255.255, 18.255.255.255 • Address 0.0.0.0 means “default route” • Address 127.0.0.0 means “this node” (local loopback). Message sent to this address will never leave the local host • Address 255.255.255.255 is reserve to broadcast to every host on the local network (limited broadcast)

  10. Class B Class A C D E Problem with Class Assignment • Class A takes 50 % range • Class B takes 25 % range • Class C take 12.5 % range These leads to: • address wasteful (specially in class A) • running out of IP address

  11. How to assigns IP Address(RFC 1466) • Class A : no allocations will be made at this time • Class B: allocations will be restricted. To apply: • organization presents a subnetting more than32 subnets • organization more than 4096 hosts • class C: divided into allocated block to distributed reginal

  12. Class C Assignment • Assignment is based on the subscriber ‘s 24 month projection according to the criteria: 1. Requires fewer than 256 addresses : 1 class C network 2. Requires fewer than 512 addresses : 2 contiguous class C networks 3. Requires fewer than 1024 addresses : 4 contiguous class C networks 4. Requires fewer than 2048 addresses : 8 contiguous class C networks 5. Requires fewer than 4096 addresses : 16 contiguous class C networks 6. Requires fewer than 8192 addresses : 32 contiguous class C networks 7. Requires fewer than 16384 addresses : 64 contiguous class C networks

  13. ... 150.0.255.254 150.0.0.1 150.0.0.2 Problem with Large Network • Class B “Flat Network” more than 60,000 hosts • How to manage? • Performance?

  14. 150.0.10.1 150.0.40.1 150.0.200.1 150.0.1.1 150.0.10.2 150.0.40.2 150.0.200.2 150.0.1.2 Router Problem with Large Network • Class B “subdivided network” to smaller group with router

  15. Subnetwork Benefits • Increase the network manager’s control the address space • Easy to allocate the address space • Better network performance • Hide routing structure from remote routers, thus reducing routes in their routing tables • Subdivide on IP network number is an important initial task of network managers

  16. host ID Network ID Subnet address Host address Choose appropriate size How to assign subnet • Divide host ID into 2 pieces • Class B address such as 150.0 might use its third byte to identify subnet • subnet1 150.0.1.X X = host address range from 1-254 • subnet2 150.0.200.X

  17. Subnet Mask • 32 bit number, tell router to recognize the subnet field, call subnet mask • subnet rule: The bit covering the network and subnet part of address are set to 1 • Example class B with 24 bits mask 1111 1111 1111 1111 1111 1111 0000 0000 subnet mask = 255.255.255.0 * zero bit are used to mask out the host number resulting the network address

  18. Subnet Mask Subnet mask 255.255.255.0 for class B tells: • network has been partition to 254 subnets 150.10.1.X to 150.10.254.X • logic “and” between IP address with mask yields network address 150.10.1.55 150.10.240.243 and and 255.255.255.0 255.255.255.0 150.10.0.0 150.10.0.0 same network address

  19. Subnet Mask Bits Use contiguous subnet mask 128 64 32 16 8 4 2 1 1 0 0 0 0 0 0 0 = 128 1 1 0 0 0 0 0 0 = 192 1 1 1 0 0 0 0 0 = 224 1 1 1 1 0 0 0 0 = 240 1 1 1 1 1 0 0 0 = 248 1 1 1 1 1 1 0 0 = 252 1 1 1 1 1 1 1 0 = 254 1 1 1 1 1 1 1 1 = 255

  20. Subnet Class B Example • 255.255.0.0 (0000 0000 0000 0000) 0 subnet with 65534 hosts (default subnet) • 255.255.192.0 (1100 0000 0000 0000) 2 subnets with 16382 hosts • 255.255.252.0 (1111 1100 0000 0000) 62 subnets with 1022 hosts • 255.255.255.0 (1111 1111 0000 0000) 254 subnets with 254 hosts • 255.255.255.252 (1111 1111 1111 11000) 16382 subnets with 2 hosts

  21. Subnet Class C Example • 255.255.255.0 ( 0000 0000) 0 subnets with 254 hosts (default subnet) • 255.255.255.192 (1100 0000) 2 subnets with 62 hosts • 255.255.255.224 (1110 0000) 6 subnets with 30 hosts • 255.255.255.240 (1111 0000) 14 subnets with 14 hosts

  22. Subnet Interpretation IP Address Subnet mask Interpretation 158.108.2.71 255.255.255.0 host 71 on subnet 158.108.2.0 150.10.25.3 255.255.255.192 host 3 on subnet 150.10.25.0 130.122.34.132 255.255255.192 host 4 on subnet 130.122.34.128 200.190.155.66 255.255.255.192 host 2 on subnet 200.190.155.64 18.20.15.2 255.255.0.0 host 15.2 on subnet 18.20.0.0

  23. Class B Subnet with Router Router is used to separate network Picture from Kasetsart University

  24. Subnet Routing Traffic is route to a host by looking “bit wise AND” results if dest IP addr & subnet mask = = my IP addr & subnet mask send packet on local network { dest IP addr is on the same subnet} else send packet to router {dest IP address is on difference subnet}

  25. Type of Subnet • Static subnet: all subnets in the subnetted network use the same subnet mask • pros: simply to implement, easy to maintain • cons: wasted address space (consider a network of 4 hosts with 255.255.255.0 wastes 250 IPs) • Variable Length Subnet : the subnets may use difference subnet masks • pros: utilize address space • cons: required well managment

  26. Variable Length Subnet Mask • General idea of VLSM • A small subnet with only a few hosts needs a subnet mask that accommodate only few hosts • A subnet with many hosts need a subnet mask to accomdate the large number of hosts • Network Manager’s responsibility to design and appropriate VLSM

  27. VLSM Sample Case Picture from Kasetsart university

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