If we disable ip classless command in routers then the router will discard the packet for unknown subnets which fall winthin a kniwn major network but it forward packets via default route which belongs to different networks.
Now i want to know why the router discard packet which only fall within the known major network why not for unknown networks.
The answer from Giuseppe contains a lot of information. Much of it is good information but not really related to the answer to your question. But there is a key statement in his response which is the key to answering your question about why packets to an unknown subnet of a network for which we know some subnets are discarded. The key concept is this:"this major network is a whole, we know all subnets in use in this major network". A key assumption of classful routing is that if we know any subnet of a network then we will know every subnet that is used in that network.
So the routing logic in classful routing is fairly simple: if we are forwarding a packet to a network about which we know some subnets then we must know the particular subnet to which this packet will go. But if the packet is going to a network about which we know no subnets then it is appropriate to use the default route.
Perhaps another way of looking at the difference between classful routing logic and classless routing logic is that classful believes why should we send a packet to the default route when we believe that the subnet to which it should go does not exist? While classless routing believes that the destination subnet may exist even though we do not have a route to it in our routing table so it makes sense to use the default route.
Hi everyone, I would like to thank you in advance for any help you can provide a newcomer like myself!
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