11. Introduction to Linux network management

1. Communication protocol:

???? TCP/IP: four-layer model, namely: physical layer, network layer, Transport layer, application layer

???? Iso/osi: seven-layer model: Physical layer, Data link layer, network layer, transport layer, Session layer, presentation layer, Application layer, respectively.

The upper layer calls the downlevel interface, and the lower layer provides services to the upper layer.

Communication subnets: Physical layer, Data link layer, network layer, transport layer/physical layer, network layer, transport layer

Resource subnets: Session layer, Presentation tier, application tier/application tier

2, IP address: Located in the network layer

The IP address is comprised of a network number and a host number.

Network address: All host bits are "0"

Broadcast address: All host locations are "1"

3. Network Mask:

Used to define which is the host bit and which is the network bit.

Define the method: The network mask and the IP address bitwise "and" operation, so as to derive its network address. (1 and who have any number, 0 and who have "0")

4, IP address classification:??

	The first eight-bit group represents a method	Network address range	Private address
Class A	0 000 0000?; The first 0 is fixed	1-127; 127 as loopback address	10.0.0.0-10.255.255.255
Class B	10 00 0000?; 10? Fixed unchanged	128-191	172.16.0.0-172.31.255.255
Class C	110 0 0000?; 110? fixed unchanged	192-223	192.168.0.0-192.168.255.255
Class D	111 0 0000?; 1110? fixed unchanged	224-239
Class E		240-255

5, MAC Address: 48bits

The first 24 bits are used to distribute to vendors, and the latter 24 bits are used to assign to vendors themselves.

6, MAC Address: To achieve local communication, communication within the local LAN.

? IP Address: The realization of cross-network communication, is only used to identify the route, and finally to convert to a MAC address to achieve; Define the communication host, source and target, communication range in the global Internet.

7. Routing table: Host routing, network routing, default route

8. ARP, convert IP address to MAC address.

9, IP address configuration method:

???? Static Address: command designation, configuration file designation

???? Dynamic acquisition: DHCP acquisition, without DHCP, will get to the 169.254.x.x, can achieve local communication of this network segment.

10, network interface naming method:

???? Method One: Traditional naming:

???????? Ethernet: eth#, such as eth0, eth1, eth2

???????? PPP networks: ppp#, such as PPP1, PPP2,

???? Method Two: Predictable naming scheme (CentOS):

???????? Many different naming mechanisms are supported.

????? ? ①, firmware, topology (firmware-based naming)

????????

11. IP address configuration command

???? Method One: Ifcfg family command: is being eliminated

???????? Ifconfig: Configuring IP, Netmask

???????? Route: Configure Routing

???????? Netstat: View network connection, routing table, interface and other information

???? Method Two: Iproute2 family

???????? IP OBJECT//object as a sub-command

???????????? Addr: Configure address and mask, three-tier

???????????? Link: Configure interface information, two-tier

???????????? Route: Configuring routing information

???????? SS: Status and Statistics view.

???? Method three: NM family; network manager

???????? NMCLI: command-line tools

???????? Nmtui: Graphical tools.

The DNS server specifies:

???? Configuration file:/etc/resolv.conf

Hostname configuration: (used to identify the local host only)

???? hostname command, temporarily valid, fail after reboot

???? Configuration file:/etc/sysconfig/network

Note: Method one or two is available in distributions in Centos5, 6, 7, and method three applies to Centos7 only.

The IP address is configured on the kernel, some commands modify the configuration file, and some commands are modified to be sent directly to the kernel (the running kernel, i.e. in memory); Modifying the configuration file does not take effect immediately, but will remain in effect after a reboot, and the command configuration will take effect immediately, but will expire after the system restarts.

11.1. IP address configuration file location:

/etc/sysconfig/network-scripts/ifcfg-ifname

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11. Introduction to Linux network management