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Q. How do I configure or change existing IP address under OpenBSD operating system? How do I configure TCP / IP under OpenBSD?

A. . Under OpenBSD network interface-specific configuration stored in files located at /etc directory. First you need to find out your interface name using ifconfig command. If your interface name is pcn0, open /etc/hostname.pcn0 file for TCP/IP configuration.

The hostname.* and bridgename.* files contain information regarding the configuration of each network interface. One file should exist for each interface that is to be configured, such as hostname.fxp0 or bridgename.bridge0. However, a configuration file is not needed for lo0.

Task Find out current interface name and IP information

Type the following command at a shell prompt:
# ifconfig
Sample output:

lo0: flags=8049 mtu 33224
        groups: lo
        inet 127.0.0.1 netmask 0xff000000
        inet6 ::1 prefixlen 128
        inet6 fe80::1%lo0 prefixlen 64 scopeid 0x4
pcn0: flags=8843 mtu 1500
        lladdr 00:0c:29:7a:b5:ce
        groups: egress
        media: Ethernet autoselect (autoselect)
        inet 74.86.49.141 netmask 0xfffffff0 broadcast 74.86.49.143
        inet6 fe80::20c:29ff:fe7a:b5ce%pcn0 prefixlen 64 scopeid 0x1
pflog0: flags=0<> mtu 33224
enc0: flags=0<> mtu 1536

Task: View pcn0 interface TCP / IP configuration

Type the following command:
# cat /etc/hostname.pcn0
Sample output:

inet 74.86.49.141 255.255.255.240 NONE

Task: Change IP configuration

To set new IP address open interface configuration file /etc/hostname.pcn0
# vi /etc/hostname.pcn0
Append/modify configuration:
inet 192.168.1.5 255.255.255.0 NONE
Save and close the file.

How do I restart or update networking configuration

To reset or restart an existing interface to its default state or update state, by invoking the following, where pnc0 is the interface name:
# sh /etc/netstart pnc0

Assign ip address using ifconfig command

You can assign the address of 192.168.1.5 with a network mask of 255.255.255.0 to interface pnc0, use:
# ifconfig pnc0 inet 192.168.1.5 netmask 255.255.255.0

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