Which feature can mitigate fragmentation issues within network segments that are between GRE endpoints?

Which feature can mitigate fragmentation issues within network segments that are between GRE endpoints?
A. PMTU
B. ICMP DF bit
C. TCP Flow Control
D. TCP MSS

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2 thoughts on “Which feature can mitigate fragmentation issues within network segments that are between GRE endpoints?

  1. A – is cottect answer

    Router as PMTUD Participant at Endpoint of Tunnel

    The router has two different PMTUD roles to play when it is the endpoint of a tunnel.

    In the first role, the router is the forwarder of a host packet. For PMTUD processing, the router needs to check the DF bit and packet size of the original data packet and take appropriate action when necessary.

    The second role comes into play after the router has encapsulated the original IPv4 packet inside the tunnel packet. At this stage, the router acts more like a host with respect to PMTUD and in regards to the tunnel IPv4 packet.

    The first example shows what happens to a packet when the router (at the tunnel source) acts in the role of forwarding router. Remember that to process PMTUD, the router needs to check the DF bit and packet size of the original data packet and take appropriate action. This examples uses GRE encapsulation for the tunnel. As can be seen, GRE does fragmentation before encapsulation.

    https://www.cisco.com/c/en/us/support/docs/ip/generic-routing-encapsulation-gre/25885-pmtud-ipfrag.html

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