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Community Member

subnetting

How does this work, on our router we pointed 2 routes 172.16.0.0 255.255.0.0 and 172.16.0.0 255.255.224.0 to different routers, The mask apparently tells the router to forward the other half of the 172.16.x.x addresses to a different network ? How does this mask work and how is this worked out here ?

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Community Member

Re: subnetting

The first route 172.16.0.0/16 (classful) tells your router to send all traffic destined to the 172.16.0.0/16 network to router A. The second route, 172.16.0.0/19 (classless) tells your router to send all traffic destined for the 172.16.0.0/19 network to router B. Because routes are selected first off of most specific route, if you ping 172.16.0.1, the router will forward the IP packets to router B, because 172.16.0.0/19 is more specific for the 172.16.0 network, than the route 172.16.0.0/16. If you ping 172.16.32.1, the router will select router A because the 172.16.0.0/16 route is more specific for the network 172.16.

Valid host ranges for the 172.16.0.0/19 network are 172.16.0.1 - 172.16.31.254. If you try to ping any IP address in that range the router will choose the route to router B.

Hope that helps.

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