CCNA Basic concepts and knowledge points

Seven-layer protocol and related instructions
Physical layer Device: hub, Repeater, encoder-decoder, transmission media connector
Hubs connect devices that share the same bandwidth in the same conflict domain, the same broadcast domain.
Data Link Layer:
Network Bridge (software-based) = switch (hardware-based)
The switch has its own conflict domain
Network Layer (IP/IPX): Provides logical addressing, that is, how the data goes.
Routers: Broadcast information control, multicast information control, path optimization, traffic management, logical addressing, providing WAN connectivity
Transport Layer (tcp/udp/spx): Distinguish between different upper layer applications, establish end-to-end connections between applications, define flow control, provide reliable (3-time handshake) or unreliable connection services for data transmission.
Presentation layer:
Application layer: Tftp,ftp,nfs,smtp,telnet RLOGIN snmp,dns
Host to host layer: TCP (connection-oriented), UDP (non-connection-oriented)
Tcp:ftp 21; TELNET 23; SMTP 25;
UDP:TFTP 69; SNMP 161; RIP 520;
DNS 53, both TCP and UDP
—————————— – Gorgeous split line —————————— –
Basic protocol Description:
IP protocol: Responsible for addressing and routing packets between the host and the network.
ARP protocol: the abbreviation for address resolution Protocol (Addresses resolution Protocol). Know IP address, request MAC address
RARP: Know MAC address, request IP address
ICMP protocol: Sends a message and reports a delivery error about the packet.
IGMP protocol: The IP host reports thousands of host group members to the local multicast router.
TCP: Transmission Control Protocol (reliable connection)
UDP: User Datagram Protocol (unreliable connection)
—————————— – Gorgeous split line —————————— –
Command:
Tracert
Pathping
Subnetting
—————————— – Gorgeous split line —————————— –
IP Address Description:
Www.111cn.net IP Address: IPV4 32bit. 192.168.0.251 (this representation is called dotted decimal)
Class A: The top 8 is a 24-seat network seat. The first 8 bits begin with 0, (0-127)
Class B: The top 16 is the 16-seat network seat. The first 8 bits begin with 10, (128-191)
Class C: The top 32 is the network position after 8 seats. The first 8 bits begin with 110, (192-223)
Class D: Multicast Addresses
Class E: For scientific research
Special Address:
Local loopback test Address: 127.0.0.1-127.255.255.255 Ping the network card
Full network broadcast address: 255.255.255.255
The host location is 1 for the local network broadcast address: such as 192.168.2.255, 129.137.255.255;
Any network: 0.0.0.0
Private IP address (cannot appear on the public Web):
10.0.0.0 to 10.255.255.255 in Class A
Class B 172.16.0.0 to 172.31.255.255
C-Class 192.168.0.0 to 192.168.255.255
—————————— – Gorgeous split line —————————— –
Computers with network number, host number
Compute the available host addresses:
2 N-TH-2. N Main seats
Such as:
C-Class Network 2 of the 8-time Square -2=256-2=254
B-Class Network 2 of the 16-time Square -2=65536-2
Class A network 2 of 24 Times Square-2
Calculate the available network numbers:
2 N- -2.N is a network bit
Class C Network 2 of 24 Times Square-2
B-Class net 2 of 16 Times Square-2
Class A network 2 of 8 Times Square-2
Subnetting of Subnet Mask:
2 x-square -2,x for the number of borrowed masks
255.255.255.192 corresponds to 2:11111111.11111111.11111111.11000000
Find the number of subnets can be divided into: 2 of the 2-2 then 4 subnets are 192.168.0.64;162.168.0.128; (multiples of base number)
How many hosts per subnet are:
2 y-square-2, Y is the number of host digits
The subnet mask (the result called block Siz or base number) in the =256-10 of valid subnet numbers is 256-192=64 in the example above
Broadcast address = Next Subnet number-1
—————————— – Gorgeous split line —————————— –
Device Connection Description:
There is and only one port labeled "X" is a different kind of device, using straight lines.
All two ports have or are not "X" means the same device, all with crossed lines.
Cross-inserting line: 1,3,2,6, other unchanged.
such as: orange White-orange-green white-blue-blue-white-green-brown white-brown
The other end is: Green white-green-orange white-blue-blue-white-orange-brown-white-brown
Dte:data Terminal Equipment Data terminal equipment, i.e. user devices.
Dce:data Communications Equipment Data communication equipment.
The last communication device of the WAN service provider; DCE provides the clock. Common DCE devices such as modem mode
AUI interface to turn RJ45 port. AUI connectors are DB15
AUX, Remote connection configuration port
S0/s1
Console configuration Port
ISDN BRI Port
Warning: You cannot connect a non-ISDN device to a router's ISDN product, otherwise damage the device!
Console connection:
RJ45 (console port)-rj45todb9 adapter-pc
1, the PC needs a RJ45 conversion to DB-9 or DB25 converter.
2, the communication port set to 9600 baud rate, 8 data bits, do not set parity bit, 1 stop bit, not set flow control.
3, the AUX port for modem remote connection access.
—————————— – Gorgeous split line —————————— –
CDP (Cisco Discovery Protocol) Protocol: Cisco Discovery Protocol
A block that provides information about the device directly adjacent to it has tools.
CDP is the protocol that can discover directly adjacent devices regardless of which devices are running.
Using CDP
#sh CDP?
#cdp Run (Global)
#no CDP Run
Close on interface
#interface serial0
# (NO) CDP enable
#sh CDP Neighbors
#sh CDP Entry * More details
CDP Traffic #sh CDP traffic
CDP interface Interface #sh CDP
—————————— – Gorgeous split line —————————— –
Connect to a gratuitous device with Telnet
#telnet 10.2.2.2
.... Display information about the device
switchb# (telnet connection to SWITCHB)
switchb# SH Session
switchb# SH User
Suspend one telnet:ctrl+shift+6 and press X when released
Quick press two times to return to session.
#disconnect close the current session
#clear Line 11 to close a session established by a remote device
Viewing version information Register values
#show version
#configure Terminal
#config-register 0x2102 Config Register value
—————————— – Gorgeous split line —————————— –
Configure the Www.111cn.net relay in the frame on the router
(config) #int s0/0
(config-if) #encapsulation Frame-relay
(config-if) #no shutdown
(config-if) #ip address 12.12.12.3 255.255.255.0
When configured, you will need to wait for the route to automatically get the DLCI number. DLCI number?
#show Frame-relay Map//view DLCI number, and finally use showping to verify that the link is not pass
—————————— – Gorgeous split line —————————— –
NET mask for changing eldest son
1, VLSM
Variable eldest subnet mask: It is from their host number to borrow a certain number of digits to do the network number, that is, increase the number of digits in the network.
The number of digits that can be used by various networks to delimit molecular networks is: A class has 24 can borrow, B class has 16 can borrow, C class has 8 can borrow; however, the actual available number of digits is: A class has 22 can borrow, B class has 14 can borrow, C class has 6 can borrow. Because the IP address must have a part of the host number, and the host part of the remaining 1 bits is meaningless.
Cases:
Network address: 192.168.0.0/27, what is the range of available addresses?
With a known network prefix of 27, the number of host digits equals =4*8 (4 8-bit binary)-the network prefix 27=5, then the number of host number is 5, then the available host IP is 2 of the 5 32,32 and then minus 2 (a network address, a broadcast address) =30;30 is the real available IP.
The available IP host address range is 192.168.0.1~192.168.0.30. Subnet mask is 255.255.255.224 (derived from prefix)
Conversion between binary and decimal:
Binary 1 1 1 1 1 1 1 1
Decimal 128 64 32 16 8 4 2 1
128 + 64 + 32 + 16 + 8 + 4 + 2 + 1
255 = 64x2+ 32x2+ 16x2+ 8x2 + 4x2 + 2x2 + 1x2 + 1
Example 1: decimal binary to 200
Decimal 128 64 32 16 8 4 2 1
200 1 1 0 0 1 0 0 0
Can be seen as above 200 equals 128+32+0+0+8+0+0+0 (actually is 128+32+8)
Example 4: A binary conversion of 11010101 to decimal.
<1>1, there, +128.
<2>1, there, +64.
<3>0, No.
<4>1, there, +16.
<5>0, No.
<6>1, there, +4.
<7>0, No.
<8>1, there, +1.
Result: Then it's 128+64+16+4+1=213.
—————————— – Gorgeous split line —————————— –
2, CIDR
3, RIP RIPv2
4, EIGRP
5, OSPF
6, Is-is
7. BGP
The TTL value defaults to 255 minus 1 per router value