1 IP Address Computer Network System Sirak Kaewjamnong

2 Three Level of Address Host name –ratree.psu.ac.th Internet IP address – (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 Converting Host Name to MAC Address cs05.cs.psu.ac.t h :50:ba:49:9d :b9 Resolve IP address by Domain Name System(DNS) Resolve MAC address by Address Resolution Protocol(ARP)

4 IP Address with Router 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 Interne t

5 Addressing Concept Partitions address into 2 fields *network address *node address

6 IP Address NetworkHost 32 bits 8,16,24 bits 8 bits 32 bits

7 IP Address Class 32 bits address length, contain 2 parts Network identifier Host identifier Class A Host IDNetwork ID0 Multicast Address1110 Unused11110 Host IDNetwork ID110 Host IDNetwork ID10Class B Class C Clas s D Clas s E

8 IP Address Class A ,677,214 B ,534 C D E Class Initial bits Bit net Bit host range address spaces usable

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

10 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 Class A Class B C D E

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 addresses : 64 contiguous class C networks

13 Problem with Large Network Class B “ Flat Network ” more than 60,000 hosts –How to manage? –Performance ?

14 Problem with Large Network Class B “ subdivided network ” to smaller group with router 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 How to assign subnet Divide host ID into 2 pieces Class B address such as might use its third byte to identify subnet –subnet X X = host address range from –subnet X Network IDSubnet addressHost address host ID Choose appropr iate size

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 subnet mask = * zero bit are used to mask out the host number resulting the network address

18 Subnet Mask Subnet mask for class B tells: network has been partition to 254 subnets X to X logic “ and ” between IP address with mask yields network address and and same network address

19 Subnet Mask Bits Use contiguous subnet mask = = = = = = = = 255

20 Subnet Class B Example ( ) 0 subnet with hosts (default subnet) ( ) 2 subnets with hosts ( ) 62 subnets with 1022 hosts ( ) 254 subnets with 254 hosts ( ) subnets with 2 hosts

21 Subnet Class C Example ( ) 0 subnets with 254 hosts (default subnet) ( ) 2 subnets with 62 hosts ( ) 6 subnets with 30 hosts ( ) 14 subnets with 14 hosts

22 Subnet Interpretation IP AddressSubnet mask Interpretation host 71 on subnet host 3 on subnet host 4 on subnet host 2 on subnet host 15.2 on subnet

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 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