Modifying the ifconfig-#.options File

Modifying the ifconfig-#.options File

There are four nondefault network parameters that can be set in the ifconfig-#.options file:

netmask
broadcast address
Address Resolution Protocol (ARP)
route metric

These steps show how to set the nondefault network parameters:

Using the netstat command, determine the order assigned to the network interface at configuration time:
/usr/etc/netstat -i
Using vi or any editor, open or create the file /etc/config/ifconfig-#.options, where the pound sign (#) represents the network interface's name. For example, to configure a primary interface, open or create the file /etc/config/ifconfig-1.options.
To change the network mask value for a network interface, enter a line with the word netmask followed by a space and either the 32-bit hexadecimal value, Internet address dot-notation, or the pseudo-network name:
netmask 0xffffff00
See "Turning On Multicast Routing" for more details regarding netmasks.
To change the broadcast address for a network interface, enter a line with the word broadcast followed by a space and the dotted decimal IP broadcast address:
broadcast 189.92.6.0
To enable or disable the Address Resolution Protocol (ARP), enter a line with arp (to enable) or -arp (to disable):

arp
The ARP tables are used by some of the network management tools (netstat, ifconfig, and so on) and provide the administrator with invaluable network information.
To change the routing metric count for a network interface, enter a line with the word metric followed by a space and the count:
metric 7
The default metric count, also called hops, is 0. The routed daemon monitors the number of hops required to route data from one network to another. If you want to reduce network traffic on a particular route, increase the metric count on the appropriate router.

The interface configuration file for the secondary interface might look like the following:

cat /etc/config/ifconfig-2.options

netmask 255.255.255.0 broadcast 129.38.50.0 -arp metric 4

The interface configuration file above indicates that the Class B network is subnetted using 8 bits of the host ID for the subnet. It uses 0 as the broadcast address instead of the default 1. ARP has been disabled and the metric (hop) count has been set to 4 to discourage router traffic.