Overview of TCP/IP, Static Routing, and CDP protocols

Understanding the TCP/IP protocol is the basis for learning the configurations of routers and switches. Understanding and configuring static routes is the basis for understanding and configuring dynamic routing protocols; as an auxiliary debugging tool for Cisco devices. CDP is also an important protocol.
This section describes TCP/IP. Static Routing and CDP-related technologies are briefly summarized.

1. TCP/IP protocol
TCP/IP is a collection of a series of related protocols based on the TCP protocol and IP protocol, also known as the TCP/IP protocol set or TCP/IP protocol stack, referred to as the IP protocol.
For the IP protocol, CCNA has been comprehensively examined, including IP, TCP, UDP, ICMP, ARP. DNS.
From the perspective of the experiment, the IP protocol should focus on the following aspects.
IP
For the IP protocol, you should have knowledge about network classification, subnet division and calculation methods, private address space and NAT (network address translation. The division of subnets and calculation of subnet masks often make beginners feel particularly difficult. You should exercise more.

ARP
ARP (Addrcss Resolution Protocol) is a Protocol used to find the MAC address corresponding to an IP address in a LAN. In the experiment, we will demonstrate how ARP works.
ECMP
ICMP (Internet Control Messages Protocol) is part of the TCP/IP network layer Protocol, used to help Control and manage IP addresses. "ICMP completes many important tasks, such as common target accessibility tests, timeout, and redirection information.
TCP
TCP is a connection-oriented protocol. It has a wealth of features. When learning, you should master its multi-channel functions, error control, Flow Control Using window mechanisms, connection establishment and termination, and ordered data transmission.
UDP
UDP is a connectionless protocol. It does not provide transmission reliability, a window mechanism, or a function to ensure that data is received in the sending order. The UDP protocol can be compared with the TCP protocol.
DNS
DNS (Domain Name Service) is a Service that connects IP addresses and Domain names in the IP protocol. It provides two-way searching between IP addresses and domain names.
Ping and Trace
Ping and Trace are the most common network testing and diagnostic tools. We need to master their working mechanisms and usage methods. It is also very useful for the mastery of extended Ping and extended Trace.
2. Static Routing
A manually specified route is called a static route. Correct configuration of static routes is the basis for understanding the routing principles and for understanding and configuring dynamic route selection protocols.
3. CDP protocol
CDP (Cisco Discovery Protocol) is a Protocol that works on the data link layer. It is a proprietary Cisco Protocol used to discover and view simple configuration information of adjacent Cisco devices. CDP is a layer-2 protocol. It does not need to start the IP protocol or other layer-3 protocols. It is important to remember this.
The CDP protocol has two Timers: The Update Time timer and the keep time timer. By default, the former is 60 s, and the latter is 180 s. Each 60sCisco device sends a CDP message from the CDP-enabled interface. After receiving this information, the adjacent Cisco device updates its CDP neighbor table. In the CDP neighbor table of the Cisco device, the timer for the table item whose update information has just been received is set to 180 s, and the countdown starts at the same time, when the device corresponding to this table item is not received during the countdown from S to 0 s, the system will delete this device table item from the CDP neighbor table.

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