Let's say, that one has a following network topology:
www-server[eth0] <-> [ge-0/0/0]MX-router[ge-0/0/1] <-> Internet
What are the advantages of setting the Maximum Transfer Unit and Maximum Receive Unit at the web server-facing router Ethernet port? I guess if the MRU is set to 1500 bytes, then even if the server Ethernet port is set to >1500 bytes, then frames larger than 1500 bytes get dropped as quickly as possible. Otherwise they would probably get dropped somewhere at the client infrastructure when they hit the 1500 byte limitation because in service-provider core the MTU is larger than 1500 bytes. And I guess the 1500 byte MTU serves the same purpose? For example, if somehow >1500 byte packet addressed to web-server reaches the router, then for IPv4 it fragments it and for IPv6 it sends a ICMPv6 "packet too big" message back to client.