MTU test :
Let me Test it
Online MTU test allows you to test the maximum MTU size from our host to your destination. To check your MTU, simply provide your IP or DNS hostname. We will test the PMTU (Path Maximum Transfer Unit) aka maximum MTU size (unfragmented) between our host and your destination, most likely the outside of your router or firewall.
More info: Wikipedia
This online MTU test is in BETA. Please let us know, using our contact form, if you find any irregularities.