Consider the following statements about the functionality of an IP based…
2020
Consider the following statements about the functionality of an IP based router.
I. A router does not modify the IP packets during forwarding.
II. It is not necessary for a router to implement any routing protocol.
III. A router should reassemble IP fragments if the MTU of the outgoing link is larger than the size of the incoming IP packet.
Which of the above statements is/are TRUE ?
- A.
I and II only
- B.
I only
- C.
II and III only
- D.
II only
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Correct answer: D
Correct answer: II only.
Explanation:
Statement I: False. Routers modify the IP header during forwarding—for example they decrement the TTL (time-to-live) field and must update the header checksum. Other functions such as NAT also change header fields.
Statement II: True. A router can function without running any dynamic routing protocol by using static routes or a manually configured forwarding table.
Statement III: False. Intermediate routers generally do not reassemble IP fragments; reassembly occurs at the destination host. Routers typically forward fragments unchanged, and will only fragment further if the outgoing MTU is smaller than the packet and fragmentation is permitted (if the Don't Fragment bit is set, the packet is dropped and an ICMP error is sent).
Therefore, only statement II is true.