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Network Configuration—Basicsifconfig_fxp0_alias0="inet 10.0.1.33/24"ifconfig_fxp0_alias1="inet 10.0.21.1/25"To remove an alias, the -alias flag is used. You can remove aliases in any orderusing the ifconfig utility. For example, to remove the second address in theprevious example, you may use the following command:# ifconfig xl0 10.0.1.33/24 –aliasThe above command removes a specific address from the interface, regardless of theorder in which the aliases were added.There is one thing you must take care of while adding aliases to an interface—thecalculation of the subnet mask for the aliases that are from the same subnet.If you are adding aliases from the same subnet to an interface (for example192.168.10.1, 192.168.10.2 and 192.168.10.3 from a /24 subnet), you should assign thecorrect netmask to one of the IP addresses of this subnet, and the other addressesshould take the /32 subnet masks.The following example shows how to add multiple IPs from the same subnet toa network interface, and also adding addresses from other networks to the sameinterface:# ifconfig bge0 192.168.10.1/25# ifconfig bge0 192.168.10.2/32 alias# ifconfig bge0 192.168.10.3/32 alias# ifconfig bge0 172.16.31.12/24 aliasAs you may have noted, the first IP address has the correct subnet mask for itsnetwork, but the secondary addresses which are from the same subnet are using the/32 (or 255.255.255.255) subnet mask. And the last alias uses the correct subnet maskas it is from a different subnet.Configuring Media OptionsDifferent network interfaces have different capabilities based on hardware featuresand driver implementation. A list of currently supported network interface cardswith their corresponding driver name can be found in the /sys/i386/conf/GENERICkernel configuration file.[ 110 ]