IPv4 Header Field Incrementation | Cisco CCIE Security Exam 400-251

Which IPv4 header field usually increments for each subsequent packet sent?

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Which IPv4 header field usually increments for each subsequent packet sent?

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C.

The IPv4 header field that usually increments for each subsequent packet sent is the Identification field. The Identification field is a 16-bit field used to identify each datagram uniquely. This field is set to a random value by the source host, and for each subsequent packet sent, it is incremented by 1.

The purpose of the Identification field is to help the destination host reassemble fragmented packets. When a packet is fragmented, each fragment has the same Identification field value. This allows the destination host to group the fragments together to reconstruct the original packet.

The Fragment Offset field is another field in the IPv4 header that is used in fragmentation, but it does not usually increment for each subsequent packet sent. Instead, it indicates the position of the data in the original packet, and it is incremented by the amount of data in each fragment.

The Flag field is a 3-bit field used to indicate whether a packet is a fragment, and whether it is the first or last fragment in the original packet. It does not usually increment for each subsequent packet sent.

The Time To Live (TTL) field is a 8-bit field used to limit the lifetime of a packet in the network. Each router that forwards the packet decrements the TTL field by 1. The TTL field does not usually increment for each subsequent packet sent.

In summary, the Identification field is the IPv4 header field that usually increments for each subsequent packet sent, and it is used to help the destination host reassemble fragmented packets.