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[LilRedDog]

Setup MMS Clamping for PPPoE Fiber connection

MSS clamping will force a smaller MTU on your LAN interface, so (buggy) clients do not think they can use 1500-byte packets. If you activate it on the WAN interface (it's just a switch on the firewall configure took on luCi), then it's MTU will propagate to the other interfaces.