Why do web servers prevent ICMP packets where data size is big? For example if the packet size of ICMP is 1490 then we will get request time out. Imagine a server is connecting to a LAN where MTU is 1500(All network components support 1500 MTU) but when we ping the server with 1490 packet we will get request time out from server. Why do server blocks ping with those packet size. How do they block it?