Understanding the importance of router backup technology

Generally speaking, the router is establishes the LAN and the WAN Connection bridge, but at present the backup router's application is very widespread, simultaneously its function also more prominent. Cisco routers have a variety of backup technologies, today I will introduce the router's own backup technology and line backup technology.

First, the router backup technology

The router's own backup technology is designed to solve the problem of network paralysis caused by a failure of the router's port or line on its own hardware (such as memory, CPU) or software iOS or the failure of a local port.

The router's backup router requires at least one router with the same functionality as the primary router that is working, in a way that replaces the primary router and provides routing services to LAN users in the event of a primary router paralysis.

Second, find a backup router approach

For the LAN computer, in the case of the main router paralysis, how to find a backup router, mainly the following centralized methods: HSRP, dynamic routing, Proxy ARP, IRDP.

(1) Dynamic routing

For some computers, which themselves support rip dynamic routing to find routers, the disadvantage of this approach is the slow conversion between the primary router and the backup router. Cisco routers provide HSRP technology that does not require any computer setup, i.e., the switch between the primary router and the backup router is transparent to the computer, and the switch between them is faster.

Using HSRP for backup router sharing a virtual MAC address and virtual IP address, each participating HSRP's local port has a port IP address and MAC address, each router has a weight value, the highest weight as the main router to work, others do not work, when the main router is paralyzed, The second highest-weighted router will act as the primary router, and so on. Routers periodically exchange weight information to determine the working status of the router.

If the primary router does not send this packet for a period of time, the other backup routers will consider the router to be bad, and the backup router with high weights will take over the virtual MAC address and IP address and be responsible for transferring the data. Once the main router is back to normal, it will automatically switch back and take over the data transfer, after which the backup router stops transmitting and is in the backup router state. In addition, HSRP allows routers to monitor the working status of certain ports and automatically switch if the port fails.

For computers on the local area network, they have only one gateway, the virtual IP address, and all the backup work is done automatically by the router.

(2) Proxy ARP

The computer that supports proxy ARP will send ARP broadcasts to find the MAC address corresponding to the destination address regardless of the computer in the network segment or the computer in the different network segment, at which point the router that knows the destination address responds to the ARP request and broadcasts its own MAC address to the source computer. The source computer then sends the IP packet to the router and the router ends up sending the packet to the destination. When the primary router is paralyzed, the computer will continue to send proxy ARP broadcasts, and the backup router should request and transmit data.

If the primary router is paralyzed while the data is being transmitted, the communicating computer is not sending an additional proxy ARP request. There's no way to know. The primary router is paralyzed and continues to contract the router, causing the transmission to break, and the communicating computer is only sending a proxy The backup router cannot be found for transmission after an ARP request or reboot.

(3) IRDP

A IRDP-enabled computer on a local area network listens to the multicast packet of Hello from the main router and uses the backup router for data transfer if the computer no longer receives Hello information.

For some enterprises or organizations of some key business data network transmission, requiring network equipment high reliability, and need maintenance convenience, the router backup technology is the most important.

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