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How to pass traffic to correct router without full BGP table?

In the setup, there will be 2 x BGP routers capable of doing up to 400g routing (non-cisco) and 2 more BGP cisco routers capable of doing multiple 10g routing. In day to day operation, definitely, there won't be such a crazy amount of traffic.


Just for the sake of design perspective, how can I ensure that i'm able to maximize all the 4 routers' routing capacity "in theory"???

(ignore the fact of uneven traffic distribution due to AS-path, just purely academy) 


Original Plan: Pass traffic from the DC traffic (assuming it is public IP, no NAT required) using Nexus switches to the 2 x 400g router via load balancing (ie: BGP multipath using default route) injected to Nexus Core. However, the traffic destined for Router 2's upstream might end up in Router 1 first before getting re-routed to router 2.

-> Limited by the available bandwidth on the 2 x 400g router. Unable to use the 2 x 10g routers which are capable of routing as well?


Question : How can I design a more scalable network and reduce the need of traversing a random router and realize that this route can be only fulfilled by another router?

Hopefully, this can be scalable in the sense that this design will continue to work even if we go beyond 4 bgp routers with even more upstreams. 


Is full BGP table the only way to go? The core N9K is barely enough to hold full ipv4 table. 


Is there some tips on how to perform route summaries so that the nexus switches can receive all the bgp entries (without getting overloaded by the BGP entries) ? How to ensure the packets reaches the correct router the first time?

Any alternative suggestions? Use ECMP? VRRP/GLBP?


Just want to hear from the experts here how to solve this issue creatively?