Chapter 06 IP Address

Transcription

1 Chapter 06 IP Address

2 IP Address Internet address Identifier used at IP layer 32 bit binary address The address space of IPv4 is 2 32 or 4,294,967,296 Consists of netid and hosted

3 IP Address Structure 2-Layer Hierarchical Structure netid + hostid Can arrive at the destination address using netid, and finally reach the destination host using hosted

4 Routing: Delivery to Destination I/F# 13 DA= DA Forward the packet to the next hop Routing table Dest Network Addr Next hop I/F No I/F# 27 I/F# 21 Network NH= Network Host

5 IPv4 Address Formats

6 Dotted Decimal Notation Used to easily read

7 Example : Class C Address

8 Internet Example (class C): Token Ring : switching WAN (class B): Ethernet (class C): Point-to-Point WAN (class A): Ethernet

9 Special Addresses

10 Direct Broadcast Address Used to send a packet to all hosts within a specific network Can be used only for destination address All bits in hostid field = 1

11 Limited Broadcast Address Broadcast address of the current (home) network Used to send a packet to all hosts within the current network The router avoids the packet to escape the current network

12 This Network Used to send a packet to other host within the current network (Router blocks the packet) All bits in netid field = 0

13 Loopback Address Client process sends a packet to a server process running in the same host using loopback address Used for software test Can be used only for destination address The fist byte of IP address = 127

14 Classless Addressing Entire address space (2 32 addresses) is divided into blocks of different sizes x.y.z.t/n netid: The first n bits (Prefix) hostid: the remaining (32-n) bits (Suffix) Classful addressing is a special case of classless addressing. n = 8 (class A), 16 (class B), or 24 (class C)

15 Example : Classless Addressing Q: Find the block if one of the addresses is /29. A: 202 = The first address is /29. The number of addresses is or 8. The last address is /29. The first address needs to be used as the network address and the last address is kept as a special address (limited broadcast address).

16 Subnetting Site looks to rest of internet like single network

17 3-Layer Hierarchical Structure

18 Example 1 : Subnetting A company needs 12 subnets with a B class address Total 14 subnets are needed (including two with subnetid field= 00 0 and 11 1 ) Number of required bits for subnet allocation = 4 bits 12 bits are used for hostid (2 12 = 4096, but 4094 hosts in fact) Subnets X.Y.0000hhhh.hhhhhhhh (X.Y.0.0) X.Y.0001hhhh.hhhhhhhh X.Y.0010hhhh.hhhhhhhh.. X.Y.1111hhhh.hhhhhhhh (X.Y.16.0) (X.Y.32.0) (X.Y.240.0)

19 Example 1 : Subnetting (cont d)

20 Example 2 : Subnetting A company is granted a block of 64 addresses with the beginning address /26. The management has decided to allocate 32 addresses for the Central office and divides the rest of addresses between the two offices. point-to-point WAN R point-to-point WAN West R R Central R R East A network block /26

21 Example 2 : Subnetting(cont d) /27 subnet address Central office: 32 addresses /27 router address 3 addresses for the routers and /27 router address 2 special addresses /27 host address /27 host address /27 router address /27 limited broadcast address /28 subnet address West office: 16 addresses /28 host address 1 address for the routers and. 2 special addresses /28 host address /28 router address /28 limited broadcast address /28 subnet address East office: 16 addresses /28 host address 1 address for the routers and. 2 special addresses /28 host address /28 router address /28 limited broadcast address

22 Example 2 : Subnetting(cont d)

23 Private IP Address IP address space used only in private network Class A : Class B : Class C : Save public IP space Within a private network, only private IP address is used Outgoing traffic is converted to a public address Protected from attack since the private address is not exposed outside Internet Load Balancer /

24 Summary IP address structure Subnetting