Once the driver of a NIC is loaded, and that an actual NIC exists, then an instance is created. Note that multiple instances may be created if there are multiple NICs of the same kind.
Each instance of a NIC has a symbolic name so that it can be referred to. For example, an Ethernet interface is commonly named eth0, eth1 and etc. The association of a symbolic name to an actual NIC is usually based on a udev rule. You can find these rules at /etc/udev/rules.d/70-persistent-net.rules. The initial rules are determined when the system is first installed. However, the rules can be altered by hand.
This file associates NICs to symbolic names based on the MAC ID of the NIC. You can, therefore, alter the rules and/or add new ones.
Even with the driver loaded, and a name assigned, a NIC is still not very useful unless it is configured.
The most useful utility to configure a NIC is ifconfig. This utility program associates a NIC (using its symbolic name) with an IP address and the associated netmask. This utility program bypasses all the other configuration settings at /etc/network/interfaces. See the man page of interfaces to learn more about the syntax of this configuration file.
If you want to use DHCP to configure a NIC, you can use dhclient. There are two main methods to use dhclient. If you want to configure a single NIC using DHCP, use “dhclient eth ”. If you want to acquire IP settings for all the NICs, use dhclient without any arguments. You can also use dhclient to release a DHCP lease.
If you have connectivity to nodes of the same subnet, but not nodes outside of the subnet, you may have problems with the route table. To display the current route table, use the command route (by itself, without any parameters). route can also be used to change the route table. For example, you can use it to add or remove a gateway. You can also use it to directly specify how to route traffic to specific destinations.
If you have access to IP addresses, but cannot access nodes by their domain name, you may have a problem with DNS server specifications. DHCP should assign DNS servers. If it does not, you may have an problem with the configuration of the DHCP server itself. If you use a static IP address, you need to specify the DNS servers explicitly.
Edit /etc/resolv.conf to add a line like the following:
You can add as many lines as you need. Most ISPs provide at least two DNS servers for redundancy purposes.