Size VRFs against platform route and VRF limits, with RIB memory and the resource that caps you first.
The VRF count a datasheet quotes assumes small VRFs. Because every VRF shares one hardware FIB, the practical limit is set by total prefixes, so 1024 VRFs carrying 5000 routes each needs five million FIB entries no mid-range platform has. FIB exhaustion is an ugly failure: the platform starts punting to software or dropping prefixes silently, and by the time it shows as latency the fix is a hardware replacement rather than a configuration change.
VRF Capacity
Total routes = VRFs × routes per VRF; supportable VRFs is the lower of the VRF table limit and FIB limit ÷ routes per VRF.
Real VRF ceiling
max VRFs = min(VRF limit, FIB limit ÷ routes per VRF).
Total routes = VRFs × routes per VRF; supportable VRFs is the lower of the VRF table limit and FIB limit ÷ routes per VRF. The VRF count a datasheet quotes assumes small VRFs. Because every VRF shares one hardware FIB, the practical limit is set by total prefixes, so 1024 VRFs carrying 5000 routes each needs five million FIB entries no mid-range platform has.
FIB exhaustion is an ugly failure: the platform starts punting to software or dropping prefixes silently, and by the time it shows as latency the fix is a hardware replacement rather than a configuration change.
This calculator takes 5 inputs: VRFs configured, Routes per VRF, Platform FIB route limit, Platform VRF limit, RIB memory per route. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.