Question

What happens when a router receives a packet for a network that isn't listed in the routing table?

Select one:

a. The router will use RIP to inform the host the packet is undeliverable.

b. The router sends the packet to the next available router.

c. The packet is held until routing table is updated with the required address.

d. The packet will be discarded.

Each input port of a router has a local copy of the router's forwarding table.

Select one:

True

False

How many fragmentation flag bits are included in an IPv4 header?

Select one:

a. 2 bits

b. 8 bits

c. 4 bits

d. 3 bits

Fragmenting a packet adds no additional overhead to message transmission.

Select one:

True

False

All packets arriving from a WAN at a NAT router have the same destination IP address regardless of their actual destination.

Select one:

True

False

An IPv4 address is 4 bytes (32 bits) long. An IPv6 address is

Select one:

a. 6 bytes (48 bits) long.

b. 7.5 bytes (60 bits) long.

c. 8 bytes (64 bits) long.

d. 16 bytes (128 bits) long.

A flow table entry

Select one or more:

a. includes a destination port

b. includes a destination IP address

c. may include one or more counters

d. includes one or more header field values

e. includes one or more actions

How many usable addresses are there in the address block 190.23.12.0/29?

Answer:

What is the valid address range for the subnet 189.168.110.64/27?

Select one:

a. 189.168.110.65 - 189.168.110.70

b. 189.168.110.65 - 189.168.110.94

c. 189.168.110.65 - 189.168.110.78

d. 189.168.110.64 - 189.168.110.94

e. 189.168.110.65 - 189.168.110.126

What is the valid address range for the subnet 189.168.110.16/29?

Select one:

a. 189.168.110.17 - 189.168.110.22

b. 189.168.110.17 - 189.168.110.18

c. 189.168.110.16 - 189.168.110.22

d. 189.168.110.17 - 189.168.110.46

e. 189.168.110.17 - 189.168.110.30

Answer 1

Hi,

1) What happens when a router receives a packet for a network that isn't listed in the routing table?

Answer D

The packet is dropped or discarded. Router searches entry in routing table and if it didn't find any match in in table sends it to default Route. If default route is also not available it will discard the packet.

2) Each input port of a router has a local copy of the router's forwarding table.

Answer: True

Reason: Say, If packets receiving time at input ports is less than the look up time for forwarding table at the router then some packets may be dropped at input port. To overcome this scenario we maintain forwarding table at each input port.

3)How many fragmentation flag bits are included in an IPv4 header?

Answer: D - 3 Bits (Please refer IPv4 header format flags field)

1st Bit currently unused​​​​​​​.

2nd bit will tell the fragmentation allowed on the packet or not (0 - fragmentation allowed, 1 - do not fragment)

3rd bit to identify the last fragment or not.

4) Fragmenting a packet adds no additional overhead to message transmission.

Answer: False.

Fragmentation divides one packet into 2 or more packets. For each packet we need header. So fragmentation adds more bytes to message.

5) All packets arriving from a WAN at a NAT router have the same destination IP address regardless of their actual destination.

Answer : False.

2 Different types of address assignment are there. Please refer rfc2663 for more details

1.Static Address assignment: There is 1 to 1 address mapping for hosts between a private network and an external network address for the lifetime of NAT operation.

2.Dynamic Address assignment: External addresses are assigned to private network hosts or vice versa.

6) An IPv4 address is 4 bytes (32 bits) long. An IPv6 address is

Answer: D. 16 bytes (128 bits) long.

7) A flow table entry

Answer: All of the above.

Flow table contains flow entries. And Each entry in flow table contains match fields(Dest ip ,source ip, port etc),counters and actions also.

8)How many usable addresses are there in the address block 190.23.12.0/29?

Answer:6 Usable address

Given that, /29 means 29 bits from network id, remaining 3 bits for host id's.

So 8 total IP's in the above subnet. 6 Usable address (remaining two addresses reserved for special cases)

9) What is the valid address range for the subnet 189.168.110.64/27?

Answer: B 189.168.110.65 - 189.168.110.94​​​​​​​

27 Bits for network id, 5 bits for Host id

189.168.110.64 Network address

189.168.110.95 Broad cast address

10)What is the valid address range for the subnet 189.168.110.16/29?

Answer :A 189.168.110.17 - 189.168.110.22

189.168.110.16 Network Address

189.168.110.23 Broadcast address