CCNA notes (1)
Chapter 1: Internetworking
First, the network's three-tier architecture:
1. Access layer: Provide network access points, the corresponding device ports are relatively dense. Main equipment: switches, hubs.
2. Aggregation layer: The aggregation point of the access layer can provide routing decisions. Implement security filtering, traffic control, remote access. Main equipment: routing
3. Core layer: Provide faster transfer speed, no operation on the data packet
Second, OSI seven-layer network model: Protocol data unit
1. Physical layer: Rate, voltage, pin interface type Bit
2. Data link layer: Data error detection, physical address MAC Frame
3. Network layer: routing (path selection), logical address (IP) Packet
4. Transport layer: reliable and unreliable transport services, retransmission mechanism. Segment
5. Session layer: Differentiate data from different applications. The operating system works on this layer of DATA
6. Presentation layer: Implement data encoding, encryption. DATA
7. Application layer: User interface DATA
Bit, Frame, Packet, and Segment are all called: PDU (Protocol Data Unit)
Basic description of the next four layers
2.1, physical layer:
1. Media type: twisted pair, coaxial cable, fiber
2. Connector type: BNC interface, AUI interface, RJ45 interface, SC/ST interface
3. The twisted pair transmission distance is 100 meters.
4.HUB Hub: A broadcast domain, a collision domain. Flooding forwarding. Sharing bandwidth.
Straight line: Host connected to switch or HUB
Crossover: switches and switches, switches and HUB connections
Rollback: Used to manage CISCO network devices.
2.2, data link layer:
1. Switch and Bridge 2. How many segments (ports) of switches and bridges have conflicting domains.
3. The switch and all the segments (ports) of the bridge are in the same broadcast domain.
2.3, network layer:
1. Router 2. Routing implementation path selection (routing decision). Routing Table 3. WAN access. 4. Router broadcast domain mapping
2.4, transport layer:
1.TCP (Transmission Control Protocol), connection-oriented, with retransmission mechanism, reliable transmission
2. UDP (User Message Protocol), no connection, no retransmission mechanism, unreliable transmission
3. Port number: Provides the session layer to distinguish data without application. Identity service.
Third, the basic configuration commands of the experiment
Show hosts show current hostname configuration
Show sessions show current outbound TELNET sessions
Clear line XXX Clear line
+ returns directly to privileged mode
++<6> + x
Enable enter privileged mode
Disable returns from privileged mode to user mode
Configure terminal enters global configuration mode
Interface ethernet 0/1 enters Ethernet port number 1 of slot 0
Exit returns to the upper mode
End directly returns to privileged mode
1. When the CISCO CATALYST series switch does not find the "User Configuration" file during initialization, it will automatically load the Default.
Settings (default configuration) file for switch initialization to ensure that the switch works properly. 2. CISCO Router is not initialized
When the "User Configuration" file is found, the system will automatically enter the "Initial Configuration Mode" (System Configuration Dialog Mode, SETUP Mode,
STEP BY STEP CONFIG mode, standby mode), does not work properly!
1.CONSOLE PORT (Management Console Interface): Distance limit, exclusive mode.
2. AUX port (auxiliary management interface): You can attach MODEM to achieve remote management, the only way to occupy.
3. Telnet: multi-person remote management (depending on performance, number of VTY lines). Not safe.
Hostname Configure the host local ID
R6(config)#interface ethernet 0
R6(config-if)#ip address 126.96.36.199 255.255.255.0
Show version Observe the list of IOS version device working time related interfaces
Show running-config View the currently active configuration This configuration file is stored in RAM
Show interface ethernet 0/1 View the status of the Ethernet interface, etc., etc...
Reload reload the Router (restart)
Setup Manually enter the setup configuration mode
Show history View history commands (commands that have just been used recently)
Terminal history size <0-256> Set the command buffer size 0: represents no cache
Copy running-config startup-config save the current configuration
Nvram : non-volatile memory, power-off information will not be lost <-- user configuration <-- startup-config
Ram : Random access memory, power failure information is lost <-- Currently effective configuration <-- running-config
Startup-config will be actively loaded each time the router or switch is started.
Banner motd also ends with
Description description interface comment
( ++<6> ) + x
3.1, configure various passwords
Configure a password for the console port:
Line conosle 0 Go to consolo 0
Password cisco set a password to "cisco"
Login to use password when setting login
Enable password Set the plaintext enable password
Enable secret Set the password for the secret text (prior to the plaintext is used)
Service password-encryption Encryption system all plaintext passwords (weak)
Set vtp line password (Telnet)
Line vty 0 ?
3.1. Configuring a virtual loopback interface (the loopback interface is UP by default)
Inerface loopback ? Create a loopback interface
Ip address 188.8.131.52 255.0.0.0 Configuring the IP address of the interface
End exit the interface
Ping 184.108.40.206 Checking the validity of the interface
No * do the reverse operation of the configuration
DCE/DTE only exists in the WAN
Show controllers serial 0 for viewing DCE and DTE properties
The router of the DCE needs to configure the clock frequency.
Clock rate ? Configure the clock frequency of the DCE interface (system specified frequency)
Serial1 is administratively down, Line protocol is down
The port is not activated with the no shutdown command
Serial1 is down, Line protocol is down
1. The other party does not have no shutdown to activate the port.
2. The line is damaged, the interface does not have any connection cable
Serial1 is up, line protocol is down
1. The other party does not have the same Layer 2 protocol serial interface default encapsulation: HDLC
2. There may be no configured clock frequency
Serial1 is up, line protocol is up
The interface works fine.
Show cdp neighbors View CDP neighbors (without IP)
Show cdp neighbors detail View CDP neighbors (including Layer 3 IP addresses)
Show cdp entry * View CDP neighbors (including Layer 3 IP addresses)
R1(config)#no cdp run Turns off the CDP protocol in global configuration mode (affects all interfaces)
R1(config-if)#no cdp enable Disable the CDP protocol on the interface (only affects the specified interface)
Clear cdp table Clear CDP neighbor table
Show cdp interface serial 1 View CDP information for an interface
Sending CDP packets every 60 seconds (send cdp packets every 60 seconds)
HoldTime 180 seconds (the information for each CDP is saved for 180 seconds)
Ip host Set static hostname mapping
Telnet *.*.*.* The device that is being telnet needs to set the password of line vty. If you need to enter privileged mode, you need to configure enable.
Show users View "Who" Log in to the local
Show sessions View "I" telnet outgoing session
Clear line * Forces a "telnet to local" session
Disconnect * Forced interruption of "telnet out" session
Show flash: View IOS files in flash
Copy running-config tftp: Copy running-config to the tftp service
Copy tftp: running-config
Copy startup-config tftp:
Copy tftp: startup-config
Copy flash: tftp:
Copy tftp: flash:
ROM: Rom monitor is a lower-level os system than Mini IOS, similar to BIOS Mini IOS (2500 serial Router).
For boot mode, can be used for IOS upgrades
nvRam : Startup-config startup configuration file, or user profile
Configuration register starts the configuration key value, modifying it will affect the startup order of the Router
Show version View the configuration register of the router
0x0 indicates that the router is going to enter the Rom monitor mode.
0x1 Router will load the mini ios software and enter BOOT mode.0x2 Router will load IOS software in Flash. (Default config regcode)
0x2142 bypasses the process of loading startup-config, or: does not load the startup configuration, directly enter setup mode
0x2102 router default configuration key value, perform normal startup sequence.
Config-register 0x2142 modify the startup configuration key