How to check MTU with ping on ESX (or any OS)

Just keep decreasing the packet size with -s flag on the ping command:

• Note that the IP packet overhead is 20 bytes and the ICMP overhead is 8 bytes (in total 28 bytes)

• Bellow my ping didn’t start working until -s value of 1472 of padding. Add 28 bytes of IP & ICMP overhead and we can see my network equipment running with 1500 MTU :

  [root@esxhost22 ~]# vmkping -s 1474 172.22.205.4 -v
  PING 172.22.205.4 (172.22.205.4): 1474 data bytes
  
  --- 172.22.205.4 ping statistics ---
  3 packets transmitted, 0 packets received, 100% packet loss
  *** vmkping failed! (status 3) ***
  [root@esxhost22 ~]# vmkping -s 1473 172.22.205.4 -v
  PING 172.22.205.4 (172.22.205.4): 1473 data bytes
  
  --- 172.22.205.4 ping statistics ---
  2 packets transmitted, 0 packets received, 100% packet loss
  *** vmkping failed! (status 2) ***
  [root@esxhost22 ~]# vmkping -s 1472 172.22.205.4 -v
  PING 172.22.205.4 (172.22.205.4): 1472 data bytes
  1480 bytes from 172.22.205.4: icmp_seq=0 ttl=255 time=3.879 ms
  1480 bytes from 172.22.205.4: icmp_seq=1 ttl=255 time=0.261 ms
  
  
  --- 172.22.205.4 ping statistics ---
  2 packets transmitted, 2 packets received, 0% packet loss
  round-trip min/avg/max = 0.572/0.579/0.586 ms
  [root@esxhost22 ~]#
  

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