Hi We have two edge routers which are connected to ATT and Verizon separately. One of two routers is primary and second one is backup. so almost all of the time only one router work and another router is resting there. Do we have a way to bind the two router's link together, this way the bandwidth would be increase a lot? Thank you
You can't and shouldn't bind 2 independent links to two different providers. If you don't want the second router to be passive/backup, then you can load-balance your prefixes across the two ISPs or increase the bandwidth of the link with your primary ISP, which is an additional cost.
you can not get 1+1 =2, instead best way is to split the subnet in to 2 routes, and fail over each other when one link fails.
If your routers are not iBGP peers then make them so. We have found across our providers in the US that we get roughly a 60-40 inbound traffic split. Most of the outbound does leave Provider 1 but that's because you have to pick your exit somewhere and equal cost paths prefer the eBGP route over the iBGP.
It's not perfect but if you already are limited to a single /24 it is a viable solution.