1.3 Given a scenario, configure and verify network connection parameters Flashcards
Five address classes
The five address classes are as follows:
Class A: From 1 to 126; each of these permits up to 16,777,216 host addresses. There can be 126 Class A networks.
Class B: From 128 to 191; each of these permits up to 65,536 host addresses. There can be 16,382 Class B networks.
Class C: From 192 to 223; each of these permits up to 254 host addresses. There can be 2,097,150 Class C networks.
Class D: From 224 to 239; this range is reserved for activities such as multicast and is not usually available for host addresses.
Class E: From 240 to 254; this range is reserved for future use
Address class ranges come with their own built-in default subnet masks; only one can be the default per range
Class A: 255.0.0.0 or /8 for the number of bits that represent the network mask
Class B: 255.255.0.0 or /16 for the number of bits that represent the network mask
Class C: 255.255.255.0 or /24 for the number of bits that represent the network mask
Ping
The ping command is used to verify that a remote host can respond to a network connection
By default, the ping command will continuously send “pings” to the remote system until the user cancels the command (Ctrl-C). The -c option specifies a count of how many ping requests to send
ping -c 4 google.com
netstat
The netstat command is useful for displaying a variety of network information. It is a key utility when troubleshooting network issues. The following table describes common options for the netstat command
the following command will display all active TCP connections:
netstat -ta
nslookup
The nslookup command is designed to perform simple queries on DNS servers
nslookup google.com
dig
The dig command is useful for performing DNS queries on specific DNS servers
dig google.com
-f file
Use the content of file to perform multiple lookups; the file should contain one hostname per line.
-4
Only perform IPv4 queries.
-6
Only perform IPv6 queries.
-x address
Perform a reverse lookup (return the hostname when provided an IP address).
host
The host command is normally used to perform simple hostname-to-IP-address translation operations (also called DNS queries)
route
the route command can be used to display the routing table
This information can also be displayed with the ip command:
ip route show
What command can be used to modify the default router?
route add default gw 192.168.1.10
ip
The ip command is a newer command that is designed to replace a collection of commands related to network interfaces
ip [options] object command
ethtool
The ethtool command is used to display and configure network device settings, such as the transmission speed and duplex value. Typically these settings are automatically configured through a process called auto-negotiation. With auto-negotiation, two network devices determine the best speed and duplex value and use that value automatically; however, these settings can also be manually set. The ethtool command also displays or modifies other useful network device settings
ss
The ss command is used to display socket information
iwconfig
The iwconfig command is used to display or set information about wireless network interfaces
f no arguments are provided, this command displays all network interfaces
nmcli
The nmcli command is used to configure NetworkManager, a tool designed to detect and configure network connections
brctl
The brctl command is used to create, modify, or view an Ethernet bridge. An Ethernet bridge connects separate networks into a single network from the perspective of users
nmtui
The nmtui command provides a text-based interface to configure NetworkManager
/etc/sysconfig/network-scripts/
This directory is found on Red Hat–based distributions, such as Red Hat Enterprise Linux, CentOS, and Fedora. It contains a collection of files that are used to configure network devices
/etc/sysconfig/network
This file is found on Red Hat–based distributions, such as Red Hat Enterprise Linux, CentOS, and Fedora. It contains basic networking information:
/etc/hosts
The /etc/hosts file is where hostname-to-IP-address translation is defined
In most cases, this file is only used for the local host itself or hosts on the local network. Normally hostname-to-IP-address translation is handled by a DNS server
/etc/network
The /etc/network directory is the traditional location where Debian-based network files are stored. This include the Debian, Ubuntu, and MintOS distributions
Note that on some systems, such as Ubuntu, /etc/network/interfaces has been replaced by configuration files in the /etc/netplan directory
/etc/nsswitch.conf
The Name Service Switch (NSS) configuration file, /etc/nsswitch.conf, is used by applications to determine the sources from which to obtain name service information, as well as in what order
/etc/resolv.conf
The /etc/resolv.conf file contains a list of the DNS servers for the system. A typical file looks like the following
If you are using a utility such as NetworkManager to configure your network settings or are using a DHCP client, then this file is normally populated by those utilities. For servers, this file is typically manually defined
/etc/netplan
The /etc/netplan directory is the new location where network configuration files are stored on Ubuntu and some other Debian-based distributions. The format of these files is YAML (YAML Ain’t Markup Language), a file format that is similar to JSON
/etc/sysctl.conf
The /etc/sysctl.conf file is used to specify which kernel settings to enable at boot
/etc/dhcpd.conf
The /etc/dhcpd.conf file is used to configure a DHCP server. After the DHCP server packages have been installed, a sample dhcpd.conf file will be placed in the /usr/share/doc directory structure (the /usr/share/doc/dhcp*/dhcpd.conf.sample file). Usually the administrator who configures the DHCP server copies this sample file to the /etc directory and modifies it to fit the local network
Bonding
The purpose of bonding is to have the system treat multiple network interfaces as if they were a single network interface. This provides much greater bandwidth than a single network interface can manage. This section discusses the concept of bonding
Aggregation
Aggregation is the core concept of bonding. To create a network bond, you need to put together two or more network interfaces into a single cluster. This is the very definition of aggregation.
Aggregation can be managed manually, by first creating a network bond and then adding devices to the bond
Active/Passive
Network bonding supports several modes. One mode is referred to as “active-backup,” in which only one device is active and the other devices are backups in the event the active device goes down
Load Balancing
There are several bonding modes that affect load balancing. Load balancing allows the system to share the traffic between different network devices based on some criteria (speed of device, round robin, and so on)
mode=0
Balanced round robin: Packets are transmitted in a round-robin approach; each slave device gets the same number of packets
mode=2
XOR: Transmit interface is based on an XOR operation using source and destination MAC addresses
mode=3
Broadcast: All packets are broadcast on all salve devices
mode=4
802.3ad: Creates network bonds for devices that share the same speed and duplex settings. Requires ethtool be installed to perform a probe of network devices
mode=5
Adaptive transmit load balancing: Load balancing based on criteria such as the speed of the network slave devices
mode=6
Adaptive load balancing: Similar to mode=5, but also performs MAC address rewriting in the network packets
