why can I only define a prefix in 64

[hfakoor222]

Routing

for example why can't I do 100.68.3.96  255.255.255.252?

[Harold Ritter]

Hi @hfakoor222 ,

You can certainly do 100.68.3.96  255.255.255.252, as shown below.

R1#sh runn | s ip route
ip route 100.68.3.96 255.255.255.252 Null0


R1#sh ip route sta

Gateway of last resort is not set

100.0.0.0/30 is subnetted, 1 subnets
S 100.68.3.96 is directly connected, Null0

Regards,

[paul driver]

Hello
Because the network is defined by the subnet mask:

100.68.3.0/26 =
0

64

128

192

224

100.68.3.x/30  =
O

4

8

12

etc….

96

100

etc..

252

[MHM Cisco World · Accepted solution]

show ip route 100.68.3.96 longest

 
then check which prefix will appear 
check this prefix mask with subnet mask you enter are it same if it same then this subnet you enter is conflict with other subnet in router.