Backup Configuration on Router
Some business or organizations need their network devices have strong reliability and easy-maintenance to make sure their critical data mission networks are safe.
There are many Cisco router backup technologies. Here is the introduction about the router’s own backup technology and circuit backup technology. In general, the router is the bridge between LAN and WAN.
So-called router backup technologies are to resolve the failures about router’s hardware (such as memory, CPU), IOS software failure, LAN port failure, local ports of the devices connected by cripple or line failures.
The router backup requires at least one router has the same function with the primary router, if the primary router can’t work, this router could instead of it in some way, continue provides routing service for LAN users. For LAN computers, how to find the backup router when the primary router can’t work, following is some ways: proxy ARP, IRDP, dynamic routing, HSRP.
- 1. Proxy ARP
The computer which supports Proxy ARP can send ARP broadcast to looking for MAC address corresponding to purpose address when the computer is communicating with other computers which are in the same network segment or different network segment. At this time, the router that knows purpose address will respond ARP requests, and it will send it’s own MAC address broadcast to source computer, then source computer will send IP data package to the router, and finally the data package will be sent to purpose address via the router.
When the primary router can’t work, the computer will continue to send Proxy broadcast, the backup router will respond this request and transmit data.
Here is one disadvantage, if during the process of data transmission, the primary router’s breakdown happens before the computer’s Proxy ARP, so there is no way the computer get the news that the primary router is broken, it will continue to send data package to the paralyzed router, this action will lead to a transmission interruption. The backup router only can be located after the computer send next Proxy ARP or restart.
- 2. IRDP
Computer in LAN that supports IRDP can monitor “Hello” multicast packet which sent by the primary router, if the computer can’t receive “Hello” message any longer, it will use backup router for data transmission.
- 3. Dynamic Routing
For some computers, they support dynamic routing with RIP to find routers, but the disadvantage of this way is the conversion between the primary router and the backup router is slow.
- 4. HSRP
The above three ways, are mainly took in the computer, Cisco router provides a technology called HSRP, this technology doesn’t need any settings in computer, that is, for the computer, the switch between the primary router and the backup router is transparent, and the switch speed is faster.
A group router using HSRP for backup has a virtual MAC address and virtual IP address, and each LAN port has its own IP address and MAC address, and each router has a weight, the router with the highest weight will work as primary router, the others don’t work, when the primary one is broken, the router with second highest weight will work as primary router. The routers regularly exchange information to determine each one’s working condition. If the primary one doesn’t send message during a period of time, other backup routers will determine the primary router is broken, so the router with second highest weight will take over the virtual IP address and MAC address, and will be responsible for data transmission. Once the ex-primary router return to normal, everything will switch back automatically.
