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CSC 249 HW 6 Due Oct 31, 2014 CHAPTER 4 Problems Problem 1

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CSC  249  HW  6  Due  Oct  31,  2014  CHAPTER  4  Problems    Problem  1  Consider  a  router  that  interconnects  three  subnets:  Subnet  1,  Subnet  2,  and  Subnet  3.  Suppose  all  of  the  interfaces  in  each  of  these  three  subnets  are  required  to  have  the  prefix  223.1.17.0/24.    You  are  the  network  administrator,  and  have  decided  that  Subnet  1  is  required  to  support  at  least  60  interfaces,  Subnet  2  is  to  support  at  least  90  interfaces,  and  Subnet  3  is  to  support  at  least  12  interfaces.  Provide  three  network  addresses  (of  the  form  a.b.c.d/x)  that  satisfy  these  constraints.  (To  do  this  you  will  define  the  new,  appropriate  value  for  �x’   and  the  associated  value  of  �d’  in  the  a.b.c.d/x  address  format.   Problem  2  Consider a datagram network using 32-bit host addresses. Suppose a router has four
links, numbered 0 through 3, and packets are to be forwarded to the link interfaces as
follows:
Destination Address Range
Link Interface
11100000 00000000 00000000 00000000
through
11100000 00111111 11111111 11111111
0
11100000 01000000 00000000 00000000
through
11100000 01000000 11111111 11111111
1
11100000 01000001 00000000 00000000
through
11100001 01111111 11111111 11111111
2
otherwise
3
a) Provide a forwarding table that has five entries, uses longest prefix matching, and
forwards packets to the correct link interfaces.
b) Describe how your forwarding table determines the appropriate link interface for
datagrams with destination addresses:
В 11001000 10010001 01010001 01010101
11100001 01000000 11000011 00111100
11100001 10000000 00010001 01110111  Problem  3  In  Section  4.2.2  an  example  of  a  forwarding  table  (using  longest  prefix  matching)  is  given.  Rewrite  this  forwarding  table  using  the  a.b.c.d/x  notation  instead  of  the  binary  string  notation.   CSC  249  HW  6  Due  Oct  31,  2014  Problem  4  Consider  the  network  shown  below.   a) Using  Dijkstra’s  algorithm,  and  showing  your  work  using  a  table  similar  to  Table  4.3  and  class  examples,  compute  the  shortest  path  from  D  to  all  network  nodes.  b) Write  out  the  forwarding  table  for  node  D,  using  the  information  in  the  table  you  just  created.    B  3  5  D   A   10    7  1     E   C   2    Problem  5  Consider  the  network  shown  below,  and  assume  that  each  node  initially  knows  the  costs  to  each  of  its  neighbors.   a) Consider  the  distance-­‐vector  algorithm  and  show  the  distance  table  entries  at  node  z.  It  should  take  you  4  or  so  iterations  to  settle  to  the  final  table,  starting  with  many  of  the  distances  set  to  ∞  (as  they  are  unknown  initially),  and  stopping  when  no  further  updates  exist.  b) Create  the  forwarding  table  for  node  z.     
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