Redundancy is common point for today’s topologies.Especially in mission-critical networks that it is not acceptable that using only one gateway to reach a point. Because one gateway means single point of failure.
With multiple gateways, you can still reach the remote node even if that you connect fails. As soon as one of the gateway down, the link changes through other gateway. Here with the word gateway. I mean the router that router that you use to reach a point, or with redundancy, multiply routers that you can use.
Here, to connect one point to another, a virtual ip used,for example there are two routers that let you to connect another point. You build redundancy protocol based neighbourship with only one virtual IP. This virtual IP is also configured on these two routers, if any failure occurs, the traffic is routed from failure to the back way.
There are some protocols for redundancy,these are:
1. HSRP (Hot Standby Router Protocol)
2. VRRP (Victual Router Redundancy Protocol)
3. GLBP (Gatewayload Balancing Protocol)
Two of the protocols above, HSRP and GLBP is a “Cisco proprietary” [pr'prat()r]. You can use these only on Cisco devices.
Another protocol, the VRRP is a “standard based” protocol. You can sue this protocol in all vendor’s devices, like Juniper and Alcatel-Lucent.
We will discuss there of protocols with a lab example in the following articles.
So, keep on.