Network with Cisco

Internet:
1.OSI Reference Model: Physical layer, Data link layer, network layer, transport layer, Session layer, presentation layer, application layer

2.TCP/IP Model:

3.IP Address: 32-bit binary

Subnet Mask: Network part host full 1, host bit full 0
Gateway: IP address of the router
DNS server: Implementing name resolution

4.IP Address Category: Class 5
A:0nnnnnnn 00000000 00000000 00000000
b:10nnnnnn nnnnnnnn 00000000 00000000
c:110nnnnn nnnnnnnn Nnnnnnnn 00000000
d:1110
E: Reserved

5. Private Address
A:10.0.0.0/8
B:172.16.0.0-172.31.0.0/16
C:192.168.0.0-192.168.255.0/24

Traceroute www.baidu.com viewing routed devices that pass through

Corresponding device in 6.OSI model
Physical layer: Repeater, Hub Hub, Nic
Data Link layer: Bridge, switch
Network layer: Router

7. Twisted pair line sequence: 568B white orange orange white green blue white blue green white brown brown

8. Cisco routers: Permanent storage configuration with NVRAM

9. Ethernet: Operating mechanism is CSMA/CD-carrier monitoring multi-access with collision detection

10.MAC Address: 48-bit, 6-byte

11. Conflict and broadcast domains: Regardless of the number of hub connections, the same broadcast domain, the same conflict domain, the switch divides the conflict domain, is still in the same broadcast domain, the router divides the conflict domain and broadcast domain

12. How routers work
(1) Routers use routing tables to distribute packets
(2) If the destination is unknown, discard the packet
(3) The routing table holds the optimal path, not the full path.

13. Dynamic routing
(1) Distance vector: rip/eigrp
(2) Link status: Ospf/is-is

14. Common port number/etc/services view port corresponding protocol
Ftp:20/21
Ssh:22
Telnet:23
Smtp:25
dns:53
Tftp:69/udp
Dhcp:67/68/udp
Http:80
pop:110
rpc:111
Ntp:123
imap:143
snmp:161/162
mysql:3306
SQL server:1433
https:443
iscsi:3260
zabbix:10050/10051
nrpe:5666

15. Grab Bag Tool
[Email protected] Desktop]# yum-y install wireshark-gnome.x86_64

16.TCP uses a scrub window for flow control

17.VLAN
VLAN is a virtual local area network, the function is to achieve broadcast control. VLANs can be partitioned according to department or function. Trunk trunking is required to implement the same VLAN on different switches, and a three-tier switch is required for different VLAN visits.

18. Layer three switches enable two-layer functionality through the Adjacency table and three-layer functionality through FIB

19.rip v1 broadcast Update, v2 multicast update 224.0.0.9 maximum hop count 15

20.HSRP is similar to VRRP (virtual redundant routing protocol, which is the standard for IETF).

21.STP spanning tree to solve two-layer loop broadcast storm problems
(1) Select the root bridge, the only basis is the minimum bridge ID
(2) Each non-root bridge, select the root port, based on the root path is the lowest cost, the direct connection Bridge ID is the smallest, even the minimum port ID.
(3) Select a designated port for each physical segment according to the same

Answer the question:
First: What is
Then: What?
Finally: how to do

=============================================================================================================== ===

ACL: Access Control List
Standard: 1-99, only check the source IP address, apply to the nearest exit direction from the target
Extension: 100-199, detection source and destination IP address and protocol, segment number, preferably applied to the nearest source of Ingress direction

NAT: Network address translation to convert a network address to a network address
Dynamic: Many-to-many
Static: one to one
PAT: A pair of more

"TCP/IP Routing Technology (volume 1th)" IGP Classic book

Network with Cisco