Consider a datagram network using 32bit host address Suppose

Consider a datagram network using 32-bit host address. Suppose a router has four links, numbered 0 through 3, and packets are to be forwarded to the link interface as follows: Describe in detail how the forwarding table determines the appropriate link interface for datagrams with destination addresses: 200.23.30.18 200.23.20.18 200.18.1.30

Solution

4.

Farwarding Table

Link interface Destination address range

in binary form in decimal form

0 11001000 00010111 00010000 00000000 200.23.16.0

: :

: :

   11001000 00010111 00010111 11111111 200.23.23.255

1 11001000 00010111 00011000 00000000 200.23.24.0

: :

: :

   11001000 00010111 00011000 11111111 200.23.24.255

2 11001000 00010111 00011100 00000000 200.23.28.0

: :

: :

   11001000 00010111 00011111 11111111 200.23.31.255

3 otherwise ( remaining all address ranges )

-> given datagrams are :

first datagram is 200.23.30.18

second datagram is 200.23.20.18

third datagram is 200.18.1.30

-> The first IP datagram 200.23.30.18 is in the range of

200.23.28.0 ........... 200.23.31.255 . So it passes through the link interface 2 .

-> Thesecond IP datagram 200.23.20.18 is in the range of

200.23.16.0 ........... 200.23.23.255 . So it passes through the link interface 0 .

-> The third IP datagram 200.18.1.30 is not in the range of link interfaces 0, 1 and 2

So it passes through the link interface 3 .

interface link 1

|

interface link 0 <-{second ip datagram } [ Router ] {first ip datatagram} -> interface link 2

| { third ip datagram }

   interface link 3