Linux Network Management

Linux network management (youtube video Tutorial)

Iso/osi Seven-layer Model

Iso:the International Organization for Standardization International Organization for Standardization

Osi:open Systems Interconnection Model open System interconnect models

MAC address is responsible for LAN communication, IP address is responsible for external network communication

File transfer port (ftp port) default 21

WWW page port default 80

Mail Mail default port is 25 and 110

Iso/osi Seven layer model is the theoretical basis, the TCP/IP four layer model is the optimization and the actual use model

Data transfer from high-level to low-rise, receiving from bottom to top

Data transmission:

Application layer (open browser)--presentation layer (decoding jpg or ASCII or MP3 into a bit stream, 0101, if there is compression and encryption, both in this layer processing representation), the session layer (to determine whether the data need network transmission, PPT does not need, PPT will be delivered directly to the hard disk save will not be passed to the next layer, but the message is Required)--the Transport layer (determine the message port number and protocol used, TCP and Port 110. Simultaneous error checking and flow control)--network layer (write to send and accept ip, also responsible for Routing)--data link layer (write to send and accept host Mac address, responsible for transmission in lan)--physical layer (actual data transfer)

TCP/IP Four Layer model

Network interface layer (from high to low), transport layer, application layer, Internet interconnect layer

Application layer, Presentation layer, Session Layer (iso/osi), Application layer (tcp/ip)

Transport Layer (iso/osi), Transport layer (tcp/ip)

Network layer (iso/osi), Internetwork Interconnect layer (tcp/ip)

Data Link layer, physical layer (iso/osi), network interface layer (tcp/ip)

Data Link Layer (iso/osi)/network interface layer (tcp/ip): ARP protocol (address resolution PROTOCOL) translating IP addresses into MAC addresses

Network layer (iso/osi), Internetwork Interconnect layer (tcp/ip): Internet Protocol (isp), ICMP (internet Control Message Protocol)

Transport Layer (iso/osi), Transport Layer (tcp/ip): TCP protocol (transmission control protocol), UDP protocol (user datagram Protocol)

Application layer, Presentation layer, Session Layer (iso/osi), Application layer (tcp/ip): FTP, Telnet, DNS, SMTP protocol

IP Address Detailed

Routers are required for different network segments, only switches are required for the same network segment

Port ports function

Common port Numbers

ftp:20, 21

Ssh:22

Telnet:23 (23 port number is disabled because Telnet is transmitted in Plaintext)

dns:53

Http:80

Smtp:25

pop3:110

Netstat-an

-a: View all links and listening ports

-n: Displays the IP address and port number without displaying the domain name and service name

Listening indicates that the local port number is being monitored, indicating that these are native-enabled services

Established represents a link that already exists

DNS role

DNS is used to translate digital IP addresses and alphabetic domain names to each other

Gateway Gateways function

Gateway in all intranet computing access is not the data of the network segment used, The gateway is responsible for the network IP into the public ip, the public IP to the network IP

The difference between network management and proxy server

Both a proxy server and a gateway route traffic from inside a network to the Internet. A gateway, however, is more like a door to get to the Internet, while a proxy server acts like a wall that bars the inside Of the network from being exposed to the Internet. A proxy server filters which connection is allowed and while a gateway doesn ' t does any filtering.

Gateways

• For the networks to communicate, a gateway must is provided from each Network. The gateway defines what's internal to the network and what's External. If a computer needs to communicate with another computer outside the network, it must is configured with a gateway to gain Access outside the Network. Without a gateway, a computer would be unable-get out, like someone locked inside a house.

Proxy Servers

• A Proxy Server represents the network from the Outside. Any user trying to gain access to any computer inside a network with a proxy would only see the IP address of the proxy ser Ver. It acts like a barrier to hide your network by configuring the Internet options of computers within the network to first P Oint to the proxy server before going out to the Internet. It keeps computers inside the network Anonymous.

Functional difference

• A Proxy Server that does does any filtering are like a gateway, simply passing on requests from the computer to the Inter Net. A proxy server, however, is a more powerful networking component that can act as a gateway while protecting the network fr Om outside Threats. A Gateway always risks exposing A internal network to the Internet because it does no filtering. It merely routes information from within the network to the Outside.

Configuring IP addresses with files

Vi/etc/sysconfig/network-scipts/ifcfg-eth0 to set IP address, subnet mask, gateway, power on, etc.

Vi/etc/sysconfig/network to modify host names

hostname command to view host name

Hostname name1 Setting the temporary host name

vi/etc/resolv.conf to set up DNS

Linux network Environment View command ifconfig

Ifup (enable) and Ifdown (disable Nic) + NIC device name

Ifup Lo---lo means loopback, 127.0.0.1

Ifdown eth0

Netstat

-a: List all network links

-l: list only in the Listening State Network Service

-n: do not use domain name and service name, but use IP address and port number

-u: List TCP protocol ports

-t: List TCP protocol ports

-r: lists the routing list, consistent with the route command

Route

-n: View the list of routes to see the gateway

Route add default GW 192.102.1.1 temporarily set Gateway

In a server, even the network card is not able to set the gateway

Nslookup

nslookup www.baidu.com for domain name and IP address resolution

nslookup >server viewing native DNS servers

Linux Network Test Command ping

Detecting network conditions for IP or domain name development

-c: Specifies the number of ping packets

Ping 192.168.0.252

Telnet

Remote management and port probing commands

Telnet 192.168.0.252 (telnet IP port)

Traceroute

Route Trace Command

-n: use IP without domain name, faster

Raceroute www.baidu.com Print out all gateway routes that go through the IP

Wget

Download command

Tcpdump

command to grab a bag

-i: make NIC interface

-nn: convert the domain name and service in the packet to IP and port

-x: Display the contents of the packet in 16 binary and ASCII code

Port to develop the listening ports

Tcpdump-i ETH0-NNX Port 21

Linux Network Management