Previous commit sets mtu to the same value as max_rx_pkt_len. Though PMDs (at least Intel ones) consider MTU as max_rx_pkt_len minus ether header, crc bytes, vlan tags. Fixes: 73d2c1d3f33c ("examples/ip_fragmentation: support big packets") Signed-off-by: Konstantin Ananyev <konstantin.ananyev@intel.com>