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routing table, question

Level 1
Level 1

Hi all,

I`m sort of new in here, and would like to help me with one thing we need to accomplish as a home work. The question is: Let`s suppose there`s a network consisting of 1000 subnets. How many records would the routing table in each router need to have, if the optimatization doesn`t exist on either of them. The topology is not important here, but what is, is the fact, that every network is connected to two other networks ( it has two outgoing routers with two network interfaces). I`m sorry, but I`m a little bit confused here. Thank you all for help

3 Replies 3

Roman Rodichev
Level 7
Level 7

if you have 1000 networks/subnets, then you will have 1000 routes on each routers.

Jan Hrnko
Level 4
Level 4

Hi Radim,

what do you mean by "optimization doesn't exist on either of them". You mean mechanism like auto-summary or even manual summarization?

If I get your question right... If you want an router to know about every subnet, then you will need 1000 routes as mentioned above.

But if you don't consider summarization to be some optimization mechanism then you could use auto or manual summarization when using dynamic routing.

One more thing, you could add just single route to more networks by defining the route statically.

For example: You want to have an route to networks /24, /24, /24, ..., /24 and you know that these networks resides behind one single router (they are not distributed over more devices) then you could simply add just one ip route to all these networks with mask of /16:

ip route next_hop_ip/outoging_interface

So instead of having 255 different entries in the routing table, you could have just one.

Best regards,


Level 4
Level 4

Hi Radim, you can have as many as 1000 or you can have only 4 ( 2 connected and 2 static), that depends how the network is subneted and configured.

Hope this helps


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