ELA_29_IPv4_Configuration

IPv4 Configuration:

Features:

1. DHCP

2. Static

3. Virtual (Sub) Interfaces - supports single physical connected to multiple logical

i.e. 192.168.0.0/24 && 192.168.1.0/24 && 10.0.0.0/30

Tasks:

1. Explore key: Directories & Files

a. '/etc/sysconfig/network' - system-wide settings: i.e. hostname, gateway, enabled|disabled

b. '/etc/sysconfig/networking' - 'system-config-network' tool controls this directory. Don't edit it manually.

c. '/etc/hosts' - local name DB - should contain a record for the localhost: i.e.

'localhost.localdomain'

Note: Add hosts to: '/etc/hosts', for which you cannot or should not resolve via DNS

d. '/etc/sysconfig/network-scripts'

d1. Interface configuration files - describes up/down config of interfaces: i.e. eth0

d2. Control files - describes hoe interfaces are to be brought: up/down - scripts

d3. Network function files - contais key network information required for the stack

d4. 'ifup-eth' - brings up ethernet interfaces: i.e. 'eth0', 'eth1', etc.

d5. 'ifdown-eth' - brings down ethernet interfaces: i.e. 'eth0', 'eth1', etc.

e. 'ifconfig' - enumerates configuration of interfaces

Note: At minimum, a routeable, connected system has at least 2 interfaces:

1. 'lo' - loopback - 127.0.0.1

2. 'eth0' - Ethernet0 - Your routable IP/Net

e2. 'ifconfig eth0:1 192.168.0.101 netmask 255.255.255.0'

e2.1 'ping -c 3 -I 192.168.0.100 192.168.0.101' - sources traffic as: 192.168.0.101

e3. 'ifconfig eth0:2 192.168.0.102 netmask 255.255.255.0'

e4. Preserve changes across system restart/ 'NetworkManager' service restart

e4.1. 'cp -v /etc/sysconfig/network-scripts/ifcfg-eth0:1'

f. 'ifcfg eth0:3 add 192.168.0.103/24' - Does duplicate address detection & sends ARP to hosts on the same Net as the interface

f1. 'ifcfg eth0:1 delete 192.168.0.101/24' - removes the sub-interface

f2. 'ifconfig eth0:3 del 192.168.0.103' - removes the sub-interface