Which Two GRE Features Prevent Fragmentation?

BC.

The two GRE features that are configured to prevent fragmentation are:

B. IP MTU: The Maximum Transmission Unit (MTU) is the largest packet size that can be transmitted on a network. When GRE encapsulates a packet, the resulting packet size may exceed the MTU of the interface over which it will be transmitted, leading to fragmentation. To prevent fragmentation, the IP MTU must be adjusted to account for the additional overhead introduced by GRE. This can be accomplished by setting the IP MTU of the interface to a value that is slightly smaller than the actual MTU, taking into account the GRE overhead.

D. DF bit clear: The Don't Fragment (DF) bit is a flag in the IP header that indicates whether a packet can be fragmented or not. If the DF bit is set and the packet size exceeds the MTU of the interface, the packet will be dropped. To prevent this, the DF bit can be cleared in the GRE header, allowing the packet to be fragmented if necessary. However, clearing the DF bit may result in suboptimal routing, as the packet may take a longer path to reach its destination if it needs to be fragmented along the way.

A, C, and E are not directly related to preventing fragmentation in GRE:

A. TCP window size: The TCP window size is a parameter that controls the amount of data that can be sent before receiving an acknowledgment. It is not directly related to GRE or fragmentation.

C. TCP MSS: The Maximum Segment Size (MSS) is a parameter that controls the maximum size of a TCP segment. It is not directly related to GRE or fragmentation.

E. MTU ignore: The MTU ignore feature is used to allow packets to be forwarded even if they exceed the MTU of the outgoing interface. It is not directly related to GRE or fragmentation.