CSE 461: Chapter 4 Review

Question 15, page 362-3

For the network on the right, give global distance vector tables when:

  1. Each node knows only the distances to its neighbors.
  2. Each node has reported the information it had in the previous step to its immediate neighbors.
Information
at Node		 Distance to Reach Node
A B C D E F
A 0 ∞ 3 8 ∞ ∞
B ∞ 0 ∞ ∞ 2 ∞
C 3 ∞ 0 ∞ 1 6
D 8 ∞ ∞ 0 2 ∞
E ∞ 2 1 2 0 ∞
F ∞ ∞ 6 ∞ ∞ 0
Information
at Node		 Distance to Reach Node
A B C D E F
A 0 ∞ 3 8 4 9
B ∞ 0 3 4 2 ∞
C 3 3 0 3 1 6
D 8 4 3 0 2 ∞
E 4 2 1 2 0 7
F 9 ∞ 6 ∞ 7 0
Information
at Node		 Distance to Reach Node
A B C D E F
A 0 6 3 8 4 9
B 6 0 3 4 2 9
C 3 3 0 3 1 6
D 8 4 3 0 2 9
E 4 2 1 2 0 7
F 9 9 6 9 7 0
SubnetNumber SubnetMask NextHop
128.96.39.0 255.255.255.128 Interface 0
128.96.39.128 255.255.255.128 Interface 1
128.96.40.0 255.255.255.128 R2
192.4.153.0 255.255.255.192 R3
(default) R4

Question 21, page 364-5

Suppose a router has built up the routing table shown on the right. The router can deliver packets directly over interfaces 0 and 1, or it can forward packets to routers R2, R3, or R4. Describe what the router does with a packet addressed to each of the following destinations.

  1. 128.96.39.10
    Interface 0
  2. 128.96.40.12
    R2
  3. 128.96.40.151
    R4
  4. 192.4.153.17
    R3
  5. 192.4.153.90
    R4
SubnetNumber SubnetMask NextHop
128.96.170.0 255.255.254.0 Interface 0
128.96.168.0 255.255.254.0 Interface 1
128.96.166.0 255.255.254.0 R2
128.96.164.0 255.255.252.0 R3
(default) R4

Question 22, page 365-6

Suppose a router has built up the routing table shown on the right. The router can deliver packets directly over interfaces 0 and 1, or it can forward packets to routers R2, R3, or R4. Describe what the router does with a packet addressed to each of the following destinations.

  1. 128.96.171.92
     
  2. 128.96.167.151
     
  3. 128.96.163.151
     
  4. 128.96.169.192
     
  5. 128.96.165.121
     
Net/MaskLength NextHop
C4.5E.2.0/23 A
C4.5E.4.0/22 B
C4.5E.C0.0/19 C
C4.5E.40.0/18 D
C4.4C.0.0/14 E
C0.0.0.0/2 F
80.0.0.0/1 G

Question 46, page 373

The table on the right is a routing table using CIDR. (What does CIDR stand for?) Address bytes are in hexadecimal. The notation "/12" in C4.50.0.0/12 denotes a netmask with 12 leading 1 bits, that is, FF.F0.0.0. State to what next hop the following will be delivered.

  1. C4.4B.31.2E
     
  2. C4.5E.05.09
     
  3. C4.4D.31.2E
     
  4. C4.5E.03.87
     
  5. C4.5E.7E.12
     
  6. C4.5E.D1.02
     

Question 47, page 373-4

Suppose P, Q, and R are network service providers, with respective CIDR address allocations C1.0.0.0/8, C2.0.0.0/8 and C3.0.0.0/8. Each provider's customers initially receive address allocations that are a subset of the provider's. P has the following customers:

Q has the following customers:

Assume there are no other providers or customers.

  1. Give the routing tables for P, Q, and R assuming each provider connects to the other two.
    P: (C2.0.0.0/8→Q; C3.0.0.0/8→R; C1.A3.0.0/16→PA; C1.B0.0.0/12→PB)
    Q: (C1.0.0.0/8→P; C3.0.0.0/8→R; C2.0A.0.0/20→QA; C2.0B.0.0/12→QB)
    R: (C1.0.0.0/8→P; C2.0.0.0/8→Q)
  2. Now assume P is connected to Q and Q is connected to R, but P and R are not directly connected. give tables for P and R.
    The same except for the following:
    P: (C3.0.0.0/8→Q // was R)
    R: (C1.0.0.0/8→Q // was P)
  3. Suppose customer PA acquires a direct link to Q, and QA acquires a direct link to P, in addition to existing links. Give the tables for P and Q, ignoring R.
    P: (C2.0.0.0/8→Q; C2.0A.10.0→QA; C3.0.0.0/8→R; C1.A3.0.0/16→PA; C1.B0.0.0/12→PB)
    Q: (C1.0.0.0/8→P; C1.A3.0.0/16→PA; C3.0.0.0/8→R; C2.0A.0.0/20→QA; C2.0B.0.0/12→QB)