It is doable. When you access these URLs the host header in HTTP request
will be as the URL. For example
http://10.18.0.175 the host header will be
10.18.0.175
You can create as below.
regex 18 10\.18\.(0 | 254)\.17[56]
regex 19 10\.19\.(0 | 254)\.17[56]
regex 20 10\.20\.(0 | 254)\.17[56]
!
class-map type inspect http match-all Block_All
match not request header host regex 18
match not request header host regex 19
match not request header host regex 20
!
policy-map type inspect http Block_All
parameters
class Block_All
drop-connection log
!
policy-map global_policy
class inspection_default
inspect http Block_All
