CCNA Course III

of the Switch MAC Address learning Situation:

1. Receive the data frame from an interface, look up the MAC Address table of the switch according to the original MAC address of the data frame, if not found, will add the original MAC address of the data frame and receive the corresponding entry of the data frame interface, put into the MAC address table of the switch (in case the MAC has space, if no space will be put, Also does not replace the original entry).

2. Receive the data frame from an interface, look up the MAC Address table of the switch according to the original MAC address of the data frame, if there is, check whether the interface in the original entry is consistent with the interface of the currently received data frame, if it is inconsistent, the original interface will be replaced, if it is consistent, no modification will be made.

Switch forwarding conditions:

1. Receive the data frame from an interface, look up the MAC Address table of the switch based on the destination MAC address of the data frame, if not found, copy this data frame to all the interfaces except the incoming interface flooding.

2. Receive a data frame from an interface, find the MAC Address table of the switch based on the destination MAC address of the data frame, and if found, forward this data frame only from the interface corresponding to the MAC address table.

Password cracking of the router:

Ahead: Legacy routers need to remain configured

Press CTRL + C during device restart

Enter the ROM system:

Rommon 2 > Confreg 0x2142//Modify register encoded as 0x2142, purpose skip to load Startup-config in NVRAM into ROM to runing-config

Rommon 3 > Reset//restart

The router enters the empty configuration:

router#

Router#copy startup-config running-config//Manually put the original configuration, loaded into the current configuration, the original configuration will be restored

Destination filename [running-config]?

%sys-5-config_i:configured from console by console

495 bytes copied in 0.416 secs (1189 bytes/sec)

Router#conf T

Enter configuration commands, one per line. End with cntl/z.

Router (config) #enable password 123//change to new password

Router (config) #config-register 0x2102//Change the Register code back to 0x2102 to restart loading the startup-config in NVRAM

Router (config) #end

router#

%sys-5-config_i:configured from console by console

ROUTER#WR//Maintain a modified configuration

Building configuration ...

[OK]

Password recovery for the switch:

1. Power down and Add.
2. Press mode inside the 15s to keep the 15s system light from green to orange and release mode
3. Enter ROM system tip: Flash_init

Load_helper

Boot

1. Switch:flash_init
2. Switch:load_helper
3. Switch:rename Flash:config.text Flash:config.text.old
4. Switch:boot//restart
5. Switch> Enable
6. switch# Rename Flash:config.text.old Flash:config.text
7. switch# Copy Flash:config.text System:running-config
8. switch# Configure terminal
9. Switch (config) # enable secret xxxx
10. Switch (config) # exit
11. Switch#write

turn on the switch VTY Remote Management line:

switch>en

Switch#conf T

Switch (config) #

Switch (config) #int vlan 1//Enter the interface that the two layer switch uses to manage the device

Switch (config-if) #ip Add 1.1.1.1 255.255.255.0

Switch (config-if) #no sh

Switch (config-if) #exit

Switch (config) #line vty 0 4

Switch (config-line) #password 111

Switch (Config-line) #login

Switch (Config-line) #end

Vty The remote management line is logged on with a local user name and password:

router>en

Router#conf T

Router (config) #username aa password AA//define local user database

Router (config) #line vty 0 4

Router (config-line) #login Local//Set vty login mode to log in to the native user, password mode

Router (Config-line) #end

Switch port security

switch>en

Switch#conf T

Switch (config) #int F0/1

Switch (config-if) #switchport mode access//interface set to access mode

Switch (config-if) #switchport port-security//Open port security function

Switch (config-if) #switchport port-security mac-address 00E0. A394. C22E//Bind a fixed MAC address

Switch (config-if) #switchport port-security maximum 3//maximum allowed number of Macs, default 1

Switch (config-if) #switchport port-security violation? If the illegal data frame arrives at the behavior that will be taken, the default behavior shutdown

Protect Security violation protect mode silently discards the data frame

Restrict Security violation restrict mode discards the data frame and logs

Shutdown Security violation shutdown mode off interface

DHCP configuration of the service

router>en

Router#conf T

Router (config) #service DHCP//Turn on DHCP service

Router (config) #ip dhcp excluded-address 1.1.1.1 1.1.1.10/exclude certain addresses

Router (config) #ip DHCP pool A//define the address pool assigned to the client

Router (dhcp-config) #network 1.1.1.0 255.255.255.0//Address pool IP address range, and mask

Router (dhcp-config) #default-router 1.1.1.10//client received the default gateway

Router (dhcp-config) #dns-server 12.23.34.45//client received DNS server address

Router (Dhcp-config) #end

CCNA Course III