Cant Ping with packets with MTU larger than 1518 Bytes

Maybe you have already taken this into account, however:

There is no standard for a ping program.

The size specified as a parameter to the ping command may not be the "ethernet" packet length.

It may be - Frame length with CRC - default for ethernet is 1518 Frame length without the CRC - 1514 IP packet total length - 1500 IP packet total length less the IP header ICMP payload length - ? Some other number the designer fancied at the time

It may also vary (and does if I recall correctly) with the exact ping program being used. Cisco router one being different from Windows one I suspect.

I always just check with wireshark on a PC.

I seem to recall that on Windows you specify -l 1472 to get a maximal length ethernet packet (however that may well be incorrect). This I guess will be the ICMP payload length.

~ I have two routers connected connected back to back with an Ethernet ~ cable. I set MTU size on bother GigaEthernet intefaces to 1524 yet, ~ when the routers cant ping each with packets of size more than 1518 ~ when set the DF on. Any hint ?

Both mtu and ip mtu are boosted, yes?