Common interview questions for network workers: Telnet, TTL, router and switch

Interview questions ：telnet、ttl、 Routers and switches

Sort out some common interview questions , Personal experience , Suggest collection ！

Telnet What is it? ？

answer ：Telnet Agreement is TCP/IP A member of the protocol family , Is the standard protocol for remote login service , It can turn the computer used by the local user into a terminal of the remote host system .

tenlnet What are three common login methods ：

answer ： The first is login without authentication , This is a way to log in directly , But the security is not high , The second is password The way , Need to provide password , The third is AAA authentication , Account and password are required .

Questioning ： You said there was AAA authentication ,AAA What is certification ？

answer ：AAA It is a kind of authentication for users 、 Management mechanism of security functions such as authorization and billing , It can prevent illegal users from logging into the device , Enhance equipment system security , There are three authentication schemes ： Local certification 、 Not certified 、 Remote authentication .

Questioning ：Tenlnet Landing and SSH and WEB What is the difference between logging in ？
answer ：SSH It is a currently recognized protocol that provides security for remote login sessions and other network services , A key is generated when the server starts , The local SSH The client sends a request to connect to the server , The server checks the connection. The client sends data and IP Address , After confirming the validity, send the key . This process uses ciphertext transmission , Compared with tenlet Clear text transmission ,SSH The encrypted transmission is more reliable .

and web Remote management is a visual management page , The device can be managed through the mouse , Compared with Telnet and SSH This kind of command only switch management is much more convenient and simple .

TTL What is it? ？

answer ：TTL It means time to live ,IP The maximum number of network segments that a packet can pass within its lifetime , Every time you pass through a router TTL Value reduction 1, When TTL Count to 0 when , The router decides to discard the packet , And send a ICMP Message to the original sender .

Questioning ：TTL What's the role ？

answer ：TTL It is mainly used to prevent data packets from being continuously IP On the Internet, the transmission never ends, thus forming a loop , Some systems have default TTL value , adopt Ping in TTL The return value of can help us identify the operating system type .

What is the relationship between routers and switches ？

answer ： The switch is OSI The second data link layer in the seven layer model , It is a network device used to connect terminals , Can realize the exchange of data frames . Routers are network layer devices , It is used to realize the communication of different network segments in the internal network and connect to the external network , Implement different protocols 、 Interworking of different types of networks .

Questioning ： How routers and switches work ？

answer ： The router forwards data by looking up the routing table , When a packet is sent to the router , The router needs to find its own routing table , Check whether the destination address of the packet exists in the routing table , If there is a route to this host in the routing table , Then forward according to the outgoing interface and the next hop on the routing table .

The switch is through MAC Table for learning and forwarding , When a data frame is sent to the switch , We first have a meeting to check the source MAC Whether it exists in the switch MAC On the table , without , Then this source MAC Address learning progress MAC In the table . Then check the purpose MAC, If the purpose MAC Exist in MAC In the table , If yes, forward it , If not, flood . It is worth noting that , When source MAC And purpose MAC identical , This data frame will be discarded ！

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At the end

Timely encouragement , Time and tide wait for no man . If you are going to interview for a new job , Let's act quickly .