Block all websites except 3 sites

RouterOS Beginner Basics
1

Dear friends

I am using Mikrotik 750 . I need to block all websites and allow only 3 sites

a) http://www.yahoo.com
b) http://www.gmail.com
c) http://www.google.com
How can i do this without web proxy ? Can any one help me?

2

Without using the non-cacheing web proxy, is harder.

You might try something like this, untested:

Make all clients use MikroTik for DNS.

/ip dns
  set allow-remote-requests=yes cache-max-ttl=1w cache-size=2048KiB max-udp-packet-size=4096 servers=

/ip dns static
  add address=192.168.1.1 disabled=no name=blah.example.com ttl=10m

Just add static entries for everything you want to allow. It may be necessary to allow more than the exact hostnames you listed.

You, probably, will also have to change those entries from time to time. You may have to change them daily. The non-cacheing web proxy method, most likely, is significantly less labor intensive.