Im reading a Cisco Book and came across this design
router interface A interface is assigned
Hosts behind that interface are
192.168.20.66/24 and .70 /24
Interface B is given the IP address
Behind that interface..the hosts are configured with
192.168.20.20 and 25 /24
Is this "legal"..how can you have
hosts with a /24 bit subnet mask
than router interfaces with /28 subnet masks
Woulnt the /28 subnet mask force everything in the .20.x ip range
int subnets of 16, 32, 64 etc???
Thanks for clarifying that both interfaces are on the same router.
From the perspective of the router the network is 192.168.20.17 through 192.168.20.30 as you observe. From the perspective of the host behind the interface the network is 192.168.20.1 through 192.168.20.254.
A host will typically ARP for all addresses that it believes are local and will forward to its gateway all addresses that it believes are remote. So the host will ARP for any destination in the 192.168.20.x. If the router has enabled proxy arp and if the router knows where the destination subnet is, then everything works. But if the router has disabled proxy arp then the traffic will fail.
I think that it is helpful to remember that every device has its own view of what is in the network. It is best if the view of the host and of the router are the same. While I am not sure that it gets to the level of "not leagal" when the host has a different mask than the router it certainly introduces the possibility that something may not work.