I want to ask about tunnel - l2tp. I have tunnel my network, sure it can minus the hop size. But I want to ask, l2tp has a bug?? coz i have tunnel, and my client can’t send email (sometimes), but if i don’t use tunnel, my client running well. Any suggestion??
Icmp 3:4, Fragmentation Needed and Don’t Fragment was Set… it’s required for pmtud to work properly. If you receive a 1500 byte packet, you might send back a icmp 3:4 packet, which tells the other side to use smaller MTU, if they do not receive that they will continue to send you too large of packets and things break. not saying this is your problem, but definately something to look into and check.