I have a IPsec tunnel from my firewall towards AWS, the tunnel is up in both phases.

If I run traffic sniffer in the firewall, I can see interesting traffic going through, but there are MANY TCP Retransmissions, TCP Fast Retransmissions and DUP ACK packets.

My pppoe interface is set to MTU 1480, while the rest of interfaces are set to MTU 1500.

What can be causing this, how to troubleshoot?

Thank you very much!

  • 1
    There are always retransmissions on TCP connections, especially over the Internet. You have little control over it. – Ron Trunk Dec 5 '18 at 13:31

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