I'm currently troubleshooting a situation where the default-route (0.0.0.0) is disappearing.
We have actually about 1500 OSPF Routes on a CSS 11506 which is also injecting the default-route for OSPF into the AREA 0 (there is only area 0).
No, don't tell me it is a bad design only using area 0 and yes, it would be better to summarize :-)
As soon as a new SVI will be activated, the CPU of the CSS is rising and the default-route within the area disappeared and shows back up as soon as the SVI will be deactivated again.
I think the CSS is running out of routing space, Does anyone else has seen this kind of behavior ?
Now back to the question: What is the maximum amount of routes of a CSS ?
The maximum is defined by how much memory you have left in your CSS after configuring everything you need.
We have tested the CSS with 2000 OSPF routes and it was ok.
Regarding the design, I will not comment the number of OSPF routes.
But why do you need ospf on the CSS ?
Usually loadbalancers are located at the edge of the network, and it should only need 1 default route to reach the first next-hop.
The first next-hop would have 1 static route to reach the network behind the CSS.
The static is then redistributed into ospf.