This is a simple post showing how to test if large MTU is working in your network using ping tool:
When jumbo frames are not enabled in all networking devs:
# ping -s 8000 -M do -c 5 172.16.64.75 PING 172.16.64.75 (172.16.64.75) 2000(2028) bytes of data. From 172.16.64.68 icmp_seq=1 Frag needed and DF set (mtu = 1500) From 172.16.64.68 icmp_seq=1 Frag needed and DF set (mtu = 1500) From 172.16.64.68 icmp_seq=1 Frag needed and DF set (mtu = 1500) From 172.16.64.68 icmp_seq=1 Frag needed and DF set (mtu = 1500) From 172.16.64.68 icmp_seq=1 Frag needed and DF set (mtu = 1500) --- 172.16.64.75 ping statistics --- 0 packets transmitted, 0 received, +5 errors
And with enabled jumbo frames:
# ping -s 8000 -M do -c 5 172.16.64.75 PING 172.16.64.75 (172.16.64.75) 8000(8028) bytes of data. 8008 bytes from 172.16.64.75: icmp_seq=1 ttl=64 time=0.461 ms 8008 bytes from 172.16.64.75: icmp_seq=2 ttl=64 time=0.360 ms 8008 bytes from 172.16.64.75: icmp_seq=3 ttl=64 time=0.402 ms 8008 bytes from 172.16.64.75: icmp_seq=4 ttl=64 time=0.410 ms 8008 bytes from 172.16.64.75: icmp_seq=5 ttl=64 time=0.347 ms --- 172.16.64.75 ping statistics --- 5 packets transmitted, 5 received, 0% packet loss, time 3998ms rtt min/avg/max/mdev = 0.347/0.396/0.461/0.040 ms