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Network Configuration—BasicsMTUYou can adjust MTU size on network interfaces using ifconfig. Default MTU for aninterface depends on your interface characteristics and varies in different interfaces,but the default MTU size on an Ethernet interface is 1500 bytes.MTU is used to limit the size of frames that are transmitted on a physical interface.Packets larger than the MTU size will be fragmented into smaller frames if allowedaccording to the df bit in the packet's header.In a gigabit network, you may want to increase the default MTU size to a largernumber to gain better performance.Before enabling jumbo-frames, make sure all the hosts on the subnet areable to receive packets with large MTUs.For example, to set MTU size on ti0 interface to 9000 (jumbo frame), you may usethe following command:# ifconfig ti0 mtu 9000Once you change the MTU on an interface, it is recommended that you reset theinterface by using ifconfig's down and up commands. This will ensure that allconnections use the new MTU settings.ARPThe default behavior of an Ethernet interface is to use arp(4) for mapping betweenlayer2 (Ethernet) and layer3 (IP) addresses. The mapping is kept in the "ARP table".If an entry does not exist for a specific destination address, the system broadcasts anarp query to find the Ethernet address of the host.To disable talking Address Resolution Protocol (ARP) on an interface, you may usethe following command:# ifconfig fxp0 –arpThis will completely disable ARP on the xl0 interface and you will see the NOARP flagon the interface when ARP is disabled:# ifconfig xl0 | grep flagxl0: flags=88c3 metric 0mtu 1500[ 116 ]