Linux
While the average user does not encounter the Linux operating system very often, Linux is widely used to support web-based enterprise-grade applications. If you work in a data center environment, in software development, or with automation, you will almost certainly encounter and use some variant of the Linux operating system.
Linux’s most common commands used to display network configuration are ifconfig and ip. Figure 4-13 illustrates ipconfig on Ubuntu Linux.
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FIGURE 4-13 ipconfig Output on Ubuntu Linux
The fields of interest are
inet: The IPv4 address.
netmask: The subnet mask. Here, it is 255.255.240.0, so the prefix length is /28.
inet6: The IPv6 address.
prefixlen: The prefix length.
scope: Whether this is a link-local or global address. Since the IPv6 address begins with fe80, this is a link-local address.
ether: The physical address.
RX packets: The number of packets received, dropped, etc.
TS packets: The number of packets transmitted, dropped, etc.
Figure 4-14 shows the output of the ip addr command.
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FIGURE 4-14 ip addr Command on Ubuntu Linux
The output of ip addr shows the physical address, the IPv4 address (inet), and the IPv6 address (inet6). This output also includes some DHCP information: alid_lft forever preferred_lft forever means the DHCP lease lifetime is forever.
Configuring a static interface address requires editing /etc/netplan/01-netcfg.yaml, as Figure 4-15 illustrates, and then restarting the network software.
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Figure 4-15 01-netcfg.yaml File in Ubuntu Linux
You can edit the file in any text editor, such as VI or Emacs, replacing the addresses: 203.0.113.4 /24 with the correct address and the default gateway, 203.0.113.1, with the correct default gateway address. The nameservers should also be replaced with their correct values.