routing table

what is the maximum number of entries that a routing table needs to have to route traffic int class A,B,and C networks. how do i calculate this? pls help!!

Excuse my lack of knowledge, I'm not sure I understand what you meant by the "Maximum number of entries". A routing table can route to any class A,B or C network, or subnetwork of those classes as long as the routing table entries are correct. The more specific you get with the entries ranges, the more entries you will need and vice versa.

If you're asking what the requirements are for a router to send a packet to a network (class A, B, or C), then maybe this answer helps:
A router can route to any of the above networks as long as it knows "how" to reach those networks. So it's not that a router "needs" a certain number of routing table entries to know how to reach a certain network, it just needs to know where to deliver the next packet to to so it could eventually reach the desired network. If the desired network is directly attached to one of its interfaces, than the router will have a single entry on its routing table for that network telling it to simply push the packet out whatever interface that is to reach that network.. However, if a router is connected to a certain network through several routers in between, then it knows to reach that distant network by sending the packet to whatever in-between router the administrator or routing protocol specifies as the next hop.

Or are you asking if there's a limit on how many routing table entries a router can have?

I am equally confused as are the other readers.please be specific in
your questions.
If you meant by number of entries in the routing table then i beleive the memory of that router will decide the number,if you are
going to use an exhaustive static routes.
An option is to use the default route,if other entries are unknown
or are too many.