CCNA is the first step in Cisco certification. In order to better integrate CCNA learning, we can first have a general understanding of the basic knowledge of CCNA. At least say some of the frequently mentioned terms, you always have to know what it means? Some common network equipment, you always have to know what is it? There are some basic definitions of LAN and WAN.
1, network nouns:
1) Domain: formerly defined as the border of a security system. But now that it has been extended by the security system too much, a more accurate description should refer to a range.
2) Collision: in Ethernet, when two nodes transmit data at the same time, the frames sent from the two devices will collide with each other, and they will meet on the physical medium and the data will be destroyed. In simple terms it means: the collision of data.
3) Collision domain, a network segment support shared media. Combining the definition of “conflict” with the definition of “domain”.
4) Broadcast domain is the network range for broadcast frame transmission. Generally, the router sets the boundary (because router does not forward broadcast).
5), broadband the amount of information flow from one end of the network to the other end of the unit time. The basic unit is bit/s. We often say that slow internet access means bandwidth.
2, network equipment:
1) Repeat: Add network node to amplify the signal; Suppose we use network cable to transfer data from one computer to another. The transmission of data use network cable is limited by distance. Different network cable distance restrictions are also different. Some can transmit 50 meters and some can transmit 100 meters. This depends on the quality of the line and the shielding effect of the line. If we are now separated by 500 meters, it is very difficult to use network cable to transmit. Then we can indirect a repeater in the middle, so that the signal can be amplified and transmitted better.
2) Bridge, the second layer of OSI reference model, controls broadcasts, maintains address tables, and only check MAC addresses to filter network information and data packets. It does not care about protocols; it can be understood as a switch branch. Because bridges are converted based on MAC tables, there are few supported features, and the port density is small enough to control broadcasts. Maintain a MAC address table, where the MAC address is a Layer 2 address.
3) HUB-Shared Hub: Propagates signals over the network, without filtering functions and path detection or exchange, used for network concentration points.
4) Switch hub: Layer 2 data exchange equipment, wire-speed switching. MAC address learning: frame filtering, loop avoidance;
5) Router: The third layer equipment provides path selection and data forwarding.
3, LAN WAN
1) Local area network: A high-speed, low-error-rate data network with a range of several kilometers, a network with a transmission delay of less than 10ms, working in a limited geographical area, and not applying for network-related technologies through the ISP: Ethernet, Token Ring and so on. The network in the office is a local area network, but the title is called enterprise network because it is in the enterprise. The network between buildings is also local area network, but it is called building network. The community network is also local area network.
2) Side-area netwirk: A data communication network that can serve users in a very wide geographical area, and generally uses transmission equipment provided by public equipment. The more popular understanding is the Internet.
The difference between the two is still quite obvious! The technologies of the WAN and LAN are completely different and the directions are different!
4, WAN equipment
3) CSU/DSU (channel service unit/data service unit);
4), WAN switch: L3
5) ATM (asynchronous transfer mode), which is a type of network, is now replaced by Frame Relay, and Frame Relay is replaced by MPLS. Now we have proposed many parallel technologies, such as DWDM, which are some network technologies. What is network technology? I set up an MPLS network. Its forwarding mechanism is based on MPLS. The ATM network looks the same, but it is actually forwarded by ATM source.
6) switch, Layer 2 switching of the LAN.
5, WAN type
1) PSTN (public switch telephone network) public telephone network;
2) ISDN (Integrated services digital network) integrated service digital network;
3) Lsased line: DDN;
4) X.25: defines how to maintain the connection between DTE and DCE for remote terminal access and computer communication on the PDN (Public Data Network);
6) ATM (asynchronous transfer mode).
Although this information is not an important knowledge point, it is always the foundation of CCNA learning.
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