Failover, load balancing, band sharing - problem

Question

I would like to accomplish the following task:
SW-A and SW-B two separate subnets, without any contact with each other.
1. Router A would perform as a gateway for computers connected to SW-A
2. Router B would perform as a gateway for computers connected to SW-B
3. Router A transfer all of your unused band "gives" to Router B (office to run periodically and sometimes weeks or even months when it is not used, we do not want to band a wasted)
4. Router A has a band of 8/8
5. Router B has a band of 8/8 + unused band of router A
6. In case of failure of Router A router B takes over as the gateway to SW-A giving him 50% of the total band
7. In case of failure of Router B router A takes over as the gateway to SW-B giving him 75% of the total band
Is this possible? problem is point 3. and points. 5, whether Cisco can manage and share transfer unused band ? on which devices can be done? (routers, firewalls ?)
sorry for my english
Thanks
dk

Answer 1

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Posting
It might be either the partners you've spoken to are incompetent to do what you're requesting, or they and/or myself don't fully understand what you're asking.  I will say I've done load sharing (outbound) using OER/PfR with HSRP/GLBP.  Works very nice, and although there's some learning required, not really too difficult.  PfR supports ingress sharing too, but ingress sharing can be very, very difficult to deal with.  Much depends on what's on the "outside".
As to sizing a router, number of users often means little.  What's important is how much (and sometimes kind of) traffic will be passing through the router.  I've attached a Cisco document that will explain much about ISR performance for different traffic loads and kinds.