Network subnetting.
Network IP calculator allows you to create multiple logical networks from
single network - this process is called subnetting.
During this process you can calculate number of hosts and subnets for
network.
Regardless of computing process for subnetting which is described in links
below worth to mention is, that in topology table there may be one or many
routes to
identical network address with different or identical length of network
mask, for instance 192.168.0.1/24, 192.168.0.1/24 and 192.168.0.1/25 -
only the best route is chosen for routing process - in this example there
will be 192.168.0.1/25 - network address with the longest network mask/most
accurate (/25).
If next hop for network 192.168.0.1/25 will be unreachable then this network
will be removed from routing table, two identical networks from topology
table
(192.168.0.1/24) will be considered to routing table and load balancing may
occur - it depends on ruting process and routing configuration ( route maps,
PBR etc ).
Going a bit further if next hops for both networks 192.168.0.1/24 will be
unreachable then both of them will be considered unavailable by router and
removed from routing table.
Finally there suppose to be default route 0.0.0.0/0 in routing table -
literally it means: 'any network address with any mask'.
What is next hop in routing process ? Next hop in term of network address
usually means that particular network address is accessible via next hop
( usually adjacent router interface IP address ), but next hop can be also
configured as interface of the same router to which adjacent router is
connected.
Adjacent router in this case knows where particular network address is ( it
can be connected directly to this router or can be accessible by next
adjacent router )
and how to route incoming packets to this network considering his own
routing table.
More info:
IP network subnetting
here
Subnetworks
here