IPv6 Router: MTU Size Exceeded
Question
You have just configured IPv6 in your network. A packet arrives on your router that exceeds the MTU size. How will an IPv6 router respond?
Answers
Explanations
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A. B. C. D.C
In IPv6, the Maximum Transmission Unit (MTU) is set to 1280 bytes by default, which is smaller than the MTU used in IPv4. If a packet exceeds the MTU size, the router must either fragment the packet or drop it.
In this scenario, if a packet arrives on a router that exceeds the MTU size, the router will not fragment the packet. Unlike IPv4, IPv6 routers are not allowed to fragment packets. Instead, the router sends an ICMPv6 Packet Too Big message back to the source address of the packet, indicating that the packet was too large and must be fragmented.
The ICMPv6 message contains the MTU size of the link that the packet was forwarded to, allowing the source to adjust the size of the packet and resend it. The source can then fragment the packet into smaller packets that fit within the MTU size.
Therefore, option B, "The packet is kept intact and not fragmented," is the correct answer. The router will not fragment the packet, but will send an ICMPv6 Packet Too Big message back to the source address.
