If we have 2 networks N1 N2 and 2 routersR1 R2 and we want to connect N1 with N2 through R1 and keep R2 as redundancy for R1. How can we apply same rules in R1 and R2 so if R1 goes downR2 takes place?
Look in to HSRP is you are using Cisco routers. I'm sure there
are other router solutions out there. Each interface will need to
be connected to the same vlan as the network it is connected to.
For instance - R1 int. 1 and R2 int 1 would be on N1. R1 int2 and
R2 int 2 would be on N2. There also might be a cool switch trick
you could do that would monitor the interface - think spanning
tree.... if it were to ever go down, then the other interface would
come up. Many ways you can skin this cat.