Basic Introduction to Linux [Article 8], basics of linux Article 8

Basic Introduction to Linux [Article 8], basics of linux Article 8

Basic Linux network cable

568A

568B

Line sequence: Orange, orange, green, white, blue, white, green, brown, white, brown

Vswitches and vrouters

Switches: DLINK, H3C, CISCO

A Switch is a network device used for electrical signal forwarding. It can provide exclusive electrical signal channels for any two network nodes connected to the vswitch. The most common switch is an Ethernet switch. Other common problems include telephone voice switches and optical fiber switches.

Router: CISCO

A Router is a device connecting LAN and WAN over the Internet. It automatically selects and sets routes based on the channel conditions, and sends signals in the order of the best path.

OSI7 layer Network Model

Physical Layer, data link layer, network layer, transmission layer, Session Layer, presentation layer, and application layer.

TCP/IP:

Data link layer: ARP and RARP

Network Layer: IP, ICMP, and IGMP

Transport Layer: TCP, UDP, UGP

Application Layer: Telnet, FTP, SMTP, SNMP

OSI

Physical Layer: EIA/TIA-232, EIA/TIA-499, V.35, V.24, RJ45, Ethernet, 802.3, 802.5, FDDI, NRZI, NRZ, B8ZS

Data link layer: Frame Relay, HDLC, PPP, IEEE 802.3/802.2, FDDI, ATM, IEEE 802.5/802.2

Network Layer: IP, IPX, AppleTalk DDP

Transport Layer: TCP, UDP, SPX

Session Layer: RPC, SQL, NFS, NetBIOS, names, AppleTalk, ASP, DECnet, SCP

Presentation Layer: TIFF, GIF, JPEG, PICT, ASCII, EBCDIC, encryption, MPEG, MIDI, HTML

Application Layer: FTP, WWW, Telnet, NFS, SMTP, Gateway, SNMP

Protocol

An agreement is an agreement or call rule designed by both parties to achieve communication.

How http works

The three-way handshake of the TCP/IP protocol is closed four times.

How users access the Internet

DHCP Service

NAT Network Address Translation

Private address:

10.0.0.0/8 (10.0.0.0 to 10.255.255.255)

172.16.0.0/12 (172.16.0.0 to 172.31.255.255)

192.168.0.0/16 (192.168.0.0 to 192.168.255.255)

169.254.0.0/16 (169.254.0.0 to 169.254.255.255)

IP address category

Class

1.0.0.0 to 126.0.0.0

0.0.0.0 and 127.0.0 are retained

Class B

128.1.0.0 to 191.254.0.0

128.0.0.0 and 191.0.0 are retained

Class C

192.0.1.0 to 223.0000254.0

Reserved for 192.0.0.0 and 223.255.255.0

Class D

224.0.0.0 to 239.00000000255 for Multi-Point Broadcast

Class E

240.0.0 to 255.255.255.255.254 Reserved

Broadcast 255.255 for broadcast

Website access process

DNS

DNS (Domain Name System)

Oldboy. me >>> 1.1.1.1 requires DNS resolution (the DNS configured on the computer)

What can DNS do?

A record: oldboy. me >>> 1.1.1.1

CNAME: frequently used by CDN service providers

MX resolution record: XXXX@qq.com build mail service

PTR reverse resolution: 1.1.1.1 >>> email service

A record parsing process:

Browser >>> oldboy. me >>> IP address of the website server 1.1.1.1 >>> IP address corresponding to the website Server

DNS resolution process principle

Recursive query> iterative Query

DNS itself is a inverted tree structure, and its vertex is also the root ".".

Root server: 13 servers around the world.

Top-level domain names: org, com, net, me, and cc

Level 1 Domain Name: oldboy, baidu, sina

DNS domain name resolution Query

Dig www.baidu.com

View dns resolution process

Dig@8.8.8.8www.baidu.com + trace

Nslookup

Host www.baidu.com

Ping www.baidu.com

Configure the NIC

Nic profile/etc/sysconfig/network-scripts/ifcfg-eth0

IPADDR = 10.0.0.8 # This is the fixed ip address of the linux server in the local area network (LAN) Bridge Mode.

NETMASK = 255.255.255.0 # subnet mask, used to plan the network bit and host bit, generally 255.255.255.0

GATEWAY = 10.0.0.254 # IP address of the LAN GATEWAY

IPV6INIT = no # whether ipv6 is supported

View the uuid of a disk

Nic effective

Recommended ifdown and ifup

Ifdown eth0 stop eth0 Nic

Ifup eth0 start eth0 Nic

For all NICs

/Etc/init. d/network restart # All NICs

The DNS configured for the NIC takes precedence over/etc/resolv. conf. Restarting the NIC overwrites/etc/resolv. conf.

If no DNS is configured for the NIC, the/etc/resolv. the configuration in conf takes effect. If multiple NICs (DHCP acquisition method) exist, the/etc/resolv may be overwritten. conf.

To modify the Host Name

1. hostname oldboylinux

2. vi/etc/sysconfig/network

3. vi/etc/hosts

Configure the Default Gateway

First effective File

Second effective File

View Gateway

Delete or add a default gateway

Configure and view Network Information

Ifconfig

Alias IP, VIP virtual IP

Ifconfig eth0: x down stop the alias ip address.

Multiple ip addresses are configured as secondary ip addresses.

Secondary ip Format: keepalived High Availability always uses secondary ip

Nic restart alias ip failure, written as the configuration file (/etc/sysconfig/network-scripts/ifcfg-eth0: 1 ).

Lsof

If a port is known to be 333, how can I view the service name corresponding to the port?

Method 1:

Method 2:

View deleted files that are still occupied by processes

Network Check

1. ping www.baidu.com. icmp is disabled in linux. (Whether or not the expressway is accessible)

2. traceroute www.baidu.com-n (tracking Routing) basic check, whether each high-speed node has been repaired

Windows route tracking

Tracert-d www.baidu.com

3. telnet www.baidu.com 80 to check whether the web server is enabled, whether the service is started, and whether the firewall is blocked.

Nmap 10.0.0.25-p 80

Nc

Disconnected:

1. The 80 service is not enabled or the port does not exist.

2. the fw firewall is blocked.

3. The service listening port is not on the connected ip address.

4. ISP is disabled by default. Open a port.

Packet capture tool

Tcpdump

Tcpdump-n icmp-I eth0

Nmap

Windows: wireshark, sniffer, kelai network analysis.