Bridging two buildings wirelessly to use either building's internet connection as backup

[Avy_9]

i have connected two buildings wirelessly by connecting routers building A wan to building B router's lan port. and thus using buildings B's internet connection and creating two separate network subnet.
If internet fails in building B i want to use internet of building A by simply changing lan/wan port cables on both routers.
and thats the thing i cant work out.
if its of any help i am using Ubiquity's nanostation 2 loco to bridge.and link to Ubiquity's forum i asked it originally.

http://

 

[kanewolf]

To do this right, you really need a dual WAN router and two links between the buildings. Put the dual wan router in "A", bring the WAN from "B" via a wireless link to "A" and into the dual wan router. Then connect "A" devices to the dual WAN router. Send the LAN output from the dual WAN to "B" via a second link and connect all devices.

 

[Avy_9]

To do this right, you really need a dual WAN router and two links between the buildings. Put the dual wan router in "A", bring the WAN from "B" via a wireless link to "A" and into the dual wan router. Then connect "A" devices to the dual WAN router. Send the LAN output from the dual WAN to "B" via a second link and connect all devices.

connected two routers lan to lan. both buildings have their own internet connection which i was using before connection both buildings. lan to lan connection has brought all devices under same network which is fine by me but what will happen if i connect both internet to each router in their buildings. which internet connection will i be able to use? if i can use only 1 internet connection at a time how can i configure my network so that if internet in one building is down i can connect internet on other router's wan and connect all my devices to internet.

i also did a wan to lan connection creating two separate network in each buildings but i could no figure out how can i use either internet connection if one internet connection fails.

what if i always connect only one internet connection to wan port at a time and when its down i remove its cable from wan port, connect the other building's connection to its router wan and have internet on whole network again. both buildings have 15 fix devices and i already assign ip to them. will give different scopes to dhcp

 

[boosted1g]

Agian you need a special router that is dual wan capabile that can use the other connection as fallback.

You will need this in both bulldings.
Building A fallback to Building B, and Building B fallback to building A will have to be 2 completley seperate connections, you cant put BOTH of them on 1 wireless stream

Depending on internet speed and needs of the buildings you will likely be better off with this scenario:
Building A provides internet for both A and B, B has intenret connection beamed to building A as fallback.
This requires only 1 dual WAN router and you can keep all the same IP addresses and schemes for everything and significantly easier on management standpoint