What does a router do if it receives an IP packet that is larger than the MTU…
2025
What does a router do if it receives an IP packet that is larger than the MTU of the outgoing link and the DF (Don’t Fragment) bit is set?
- A.
Drops the packet and sends an ICMP "Fragmentation Needed" message
- B.
Fragments the packet and forwards it
- C.
Forwards the packet unchanged to the next router
- D.
Reassembles the packet and resends it in parts
- E.
Compresses the packet and resends it on the link
Attempted by 26 students.
Show answer & explanation
Correct answer: A
Correct answer: The router drops the packet and sends an ICMP “Fragmentation Needed” message.
MTU is the maximum packet size that can be sent on a link without fragmentation.
If the packet is larger than the outgoing link MTU, the router would normally need fragmentation to forward it.
When the DF bit is set, fragmentation is not allowed, so the router drops the packet and reports the problem using an ICMP fragmentation-needed message.