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What is the difference between a switch and a router?
A: Yes. 1 The OSI level of the work is different. The switch works in the OSI Layer 2 data link layer. The router works in the OSI Layer 3 network layer. The addressing mode is different: the switch is addressed according to the MAC address, and the router is addressed according to the IP address. 3 Different forwarding speeds: The forwarding speed of the switch is fast, and the forwarding speed of the router is relatively slow.
※Simply talk about the OSPF operation process?
Answer: 1 router sends HELLO message; 2 establishes adjacency relationship; 3 forms link state 4SPF algorithm calculates optimal path 5 to form routing table.
※STP determination process?
A: The STP decision step is: 1 determine the root bridge, use the bridge ID; 2 calculate the minimum root path cost to the root bridge; 3 determine the minimum sender bridge ID; 4 determine the minimum port ID.
The STP process is: 1 select the root bridge country; 2 select the root port on each non-root bridge; 3 calibrate a designated port on each network segment
※What is the IP packet format?
A: The IP header is as short as 20 bytes. The header format includes the following fields: version number, header length, priority, datagram length, protocol field, source IP address, and destination IP address.
※What is HSRP? How does it work?
A: HSRP is a hot backup routing protocol that is proprietary to Cisco. Through HSRP, a group of routers can work together to represent a virtual router. The backup group works like a router, a virtual IP address, and a MAC address. From the perspective of the end host, the virtual master router has its own IP. A router with an address and a MAC address, which is different from the actual physical router. If one router in the group fails, the other router takes over and the routing is as usual.
※What is the difference between RIP version 1 and version 2?
Answer: 1RIP-V1 is a classful routing protocol, RIP-V2 is a classless routing protocol; 2RIP-V1 broadcast routing update, RIP-V2 multicast routing update; 3RIP-V2 routing update carries more information than RIP-V1
※What is the problem with the three-layer switch?
A: A switch with routing capability. That is, a module with routing function is added to the Layer 2 switch.
※Ethernet three port modes implement different VLAN characteristics respectively. Please indicate three port modes?
1 access mode switch port mode access; 2 relay mode switch port mode trunk; 3 three-layer routing mode no switch port
※What are the advantages of OSPF? Why is OSPF faster than RIP convergence?
Advantages: 1. Fast convergence; 2. Supports classless routing table query, VLSM and super network technology; 3. Supports multiple cost load balancing; 4. High routing update efficiency (region, multicast update, DR) /BDR); 5, according to the bandwidth of the link, the most preferred way is to use regional, multicast update, incremental update, 30-minute retransmission LSA.
※ PPP agreement composition and a brief description of the basic process of agreement negotiation?
1. Point-to-Point Protocol (PPP) is a link layer protocol designed for a simple link that transmits data packets between peer units. The purpose of the design is mainly to establish a point-to-point connection to send data through dial-up or leased line, making it a common solution for simple connection between various hosts, bridges and routers.
2. The PPP protocol provides a complete set of solutions to solve problems such as link establishment, maintenance, teardown, upper layer protocol negotiation, and authentication.
3. The PPP protocol includes such parts as the Link Control Protocol (LCP), the Network Control Protocol (NCP), and the authentication protocol. The most commonly used ones include the Password Authentication Protocol (PAP) and the Challenge Handshake. Authentication Protocol CHAP (Challenge-Handshake Authentication Protocol).
4. A typical link establishment process is divided into three phases: the creation phase, the authentication phase, and the network negotiation phase.
Phase 1: Creating a PPP Link The LCP is responsible for creating the link.
At this stage, the basic communication method will be selected. The devices at both ends of the link send configuration information packets (ConfigurePackets) to the peer through the LCP. Once a configuration success packet (Configure-Ack packet) is sent and received, the exchange is completed and the LCP is turned on. It should be noted that during the link creation phase, only the authentication protocol is selected and user authentication will be implemented in phase 2.
Phase 2: User authentication.
At this stage, the client sends its identity to the remote access server. This phase uses a secure authentication method to prevent third parties from stealing data or impersonating remote clients to take over connections with clients. Advance from the authentication phase to the network layer protocol phase is prohibited until the authentication is completed. If the authentication fails, the authenticator should transition to the link termination phase. At this stage, only the packets of the link control protocol, the authentication protocol, and the link quality monitoring protocol are allowed. The other packets received during this phase must be silently discarded. The most commonly used authentication protocols are Password Authentication Protocol (PAP) and Challenge Handshake Authentication Protocol (CHAP). The introduction of the certification method is introduced in the third part.
Phase 3: Call the network layer protocol.
After the authentication phase is completed, PPP will invoke the various Network Control Protocols (NCP) selected during the link creation phase (Phase 1). The selected NCP resolves higher layer protocol issues on the PPP link, for example, at this stage the IP Control Protocol (IPCP) can assign dynamic addresses to dial-in users. Thus, after three stages, a complete PPP link is established.
