1. Allow only specific ip address :
order allow,deny
deny from all
allow from 192.168.1.1
allow from 192.168.1.2
2. Block specific ip address :
order deny,allow
allow from all
deny from 192.168.1.1
deny from 192.168.1.2
you can substitute ip for :
subnet -> deny from 192.168.1.0/24
subnet wild cards -> deny from 192.168.*.*
domain -> deny from domain\.com
you can also combine ip’s on one line:
deny from 192.168.1.1 192.168.2.1