Network Desing help required

pls Help

Currently I have WISP setup 7 highsite and around 150 users, the edge router is an RB1200 (3xADSL Load blanaced)

We are going to be adding another interet provider which will feed to us wirelessley, this connenction will use 2 new high site relays, and then feed into an unsed port on the RB1200, upto here I am fine and understand everything,

Here is the thing the 2 new high site have the potential of supplying around 100 more users, if i connect users to these high sites using the new backhauls, to the RB1200, they will be outside our netwrok, is it posisable to seprate the traffic, but use the same backual to the RB1200, ensuring that the client traffic is secure and considered in side the network and the internet traffic will out side, unfortunatly it’s not possialbe to add additional equipment to the WISP Provider site or any of the High Site as these are really remote and solar powered.


WISP Provider -------> High Site <-----------> High Site <------> RB1200<-------------> Network
. . . . . . . . . . . . . . . . . .|. . . . . . . . . . . . . . . . .|. . . . . . . . . . . .|
. . . . . . . . . . . . . . . . .CPE. . . . . . . . . . . . . . . CPE. . . . . . . . .3 x ADSL

Above illistrats what I am trying to do.