Reference article: Illustrated Router: Can this thing connect to networks all over the world? - Zhihu(zhihu.com)
- Macrokernel and microkernel
Macro kernel should be called single kernel or single core. In this single-core design, the kernel is a large whole, and all kernel services run in one address space. There are few call links between functions, and direct communication is simple and efficient.
The functions of the microkernel will be divided into independent processes, and processes communicate through IPC. They are highly modular and the failure of one service will not affect another service. Communication between processes through microkernel
2. IPV6 auto-configuration will append the MAC address to the address prefix to generate a link-local address.
3. Management distance refers to the routing credibility, 255->0. The larger the number, the more trustworthy it is. If it is 255, all services will not pass.
4. If there is an IP address, it means the network card is normal. But DHCP fails, you need to check the connecting optical cable
5.
6. SMTP is the protocol for sending emails, the default port is 25, POP3 is the protocol for receiving emails, the default port is 110
7. You can add a PTR record when the IP cannot resolve the server name.
8. FTP occupies ports 20 and 21, 20 is the data port, and 21 is the control port.
9. TLS is at the transport layer
10. IPSEC is IP layer security technology
11. The top-level domain name server is responsible for managing all second-level domain names registered on this top-level domain name server. The root domain name server is the highest-level domain name server.
12.DAS (Direct Attached Storage) direct-attached storage relies on the server and does not provide cross-platform storage. NAS (Network Attached Storage) has its own server and is connected to the server through a network port. SAN is a dedicated storage system that connects one or more network storage devices and servers through dedicated high-speed connections. IP SAN (Ethernet) and FC SAN (fiber optic) two environments
13. Hierarchical network design, design the access layer first, then the aggregation layer and core layer. The access layer maintains strict control over the network structure. Other layers except the access layer adopt a modular approach and are composed of multiple modules or equipment sets.
14. In the network layer design, the core layer connects server clusters, subnet switching routers and metropolitan area network interfaces. The aggregation layer brings together multiple subnets at different locations, and the access layer connects end-user computers to the network.
15. MIME has nothing to do with email. It is a type of file that is opened by an application based on a certain extension, extending the email standard.
16. The network redundant backup path will not be put into use at the same time as the main path. It will be activated after the main path fails.
17. Use show interface to check the status of each port on the car, interpret screen output signals, port status, protocol resume and EIA status data physical layer diagnosis
18. The forwarding principle of the switch is that the MAC address table is initially empty. After receiving the data frame, the corresponding MAC address table entry is added by reading the source address of the input frame. The MAC address table entry is dynamically grown. If there is no corresponding entry, the ARP flooding operation is used to forward the packet in broadcast mode.
19. SDN has application layer, control layer and forwarding layer. It means to software-ify the network and modify the network like upgrading the network installation software.
20. IPV6 addresses are increased to 128 bits, and addresses are assigned to interfaces instead of nodes, including unicast, anycast, and multicast addresses. At the same time, the IPv4 packet header format is simplified. Broadcasting is available in IPV4.
21. When the DHCP server receives the client's request, it will send DhcpOffer. If it is a wrong address, it will send DhcpDecline.
