Q. Under Linux I can use Ethtool and mii-tool, but they are not available under FreeBSD. How do I tell the port speed of the nic under FreeBSD operating system?

A. Under FreeBSD the ifconfig utility is used to assign an address to a network interface and/or configure network interface parameters.

The ifconfig utility must be used at boot time to define the network address of each interface present on a machine; it may also be used at a later time to redefine an interface’s address or other operating parameters.

It can also display port speed of the nic under FreeBSD. Simply type /sbin/ifconfig and look for media in output:
$ /sbin/ifconfig | grep media
$ /sbin/ifconfig {interface} | grep media
$ /sbin/ifconfig em0 | grep media
$ /sbin/ifconfig
Sample output:

em0: flags=8943<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST> metric 0 mtu 1500
        options=19b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,TSO4>
        ether 00:30:48:98:9c:bc
        inet 10.24.116.2 netmask 0xffffffc0 broadcast 10.24.116.63
        media: Ethernet 10baseT/UTP 
        status: active