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Setting Up access-list on cisco Router
In this Example will open ports for need to use out of using will close it alls.

This case no have inside (internal) server.
Step for setting Up :

Router#conf t
Router(config)#access-list 100 permit tcp any any range 20 23
Router(config)#access-list 100 permit tcp any any eq 25
Router(config)#access-list 100 permit tcp any any eq 53
Router(config)#access-list 100 permit tcp any any eq 80
Router(config)#access-list 100 permit tcp any any eq 110
Router(config)#access-list 100 permit tcp any any eq 143
Router(config)#access-list 100 permit tcp any any eq 443
Router(config)#access-list 100 permit udp any any eq 53
Router(config)#access-list 100 permit udp any any eq 161
Router(config)#access-list 100 permit tcp any any eq 3306
Router(config)#access-list 100 permit icmp any any echo
Router(config)#access-list 100 deny ip any any

Router(config)#int f0
Router(config-if)#ip access-group 100 in

 

This case : have inside (internal server)

Server IP for this case as below :
Web Server : 202.129.49.194
FTP Server : 202.129.49.195
DNS Server : 202.129.49.196
Mail Server : 202.129.49.197

Step for Setting Up :

Router#conf t
Router(config)#access-list 100 permit tcp any any range 20 23
Router(config)#access-list 100 permit tcp any any eq 25
Router(config)#access-list 100 permit tcp any any eq 53
Router(config)#access-list 100 permit tcp any any eq 80
Router(config)#access-list 100 permit tcp any any eq 110
Router(config)#access-list 100 permit tcp any any eq 143
Router(config)#access-list 100 permit tcp any any eq 443
Router(config)#access-list 100 permit udp any any eq 53
Router(config)#access-list 100 permit udp any any eq 161
Router(config)#access-list 100 permit tcp any any eq 3306
Router(config)#access-list 100 permit icmp any any echo
Router(config)#access-list 100 permit tcp host 202.129.49.194 eq 80 any <For Web Server>
Router(config)#access-list 100 permit tcp host 202.129.49.195 any < For FTP Server >
Router(config)#access-list 100 permit tcp host 202.129.49.196 eq 53 any < For DNS Server : tcp>
Router(config)#access-list 100 permit udp host 202.129.49.196 eq 53 any < For DNS Server : udp >
Router(config)#access-list 100 permit tcp host 202.129.49.197 eq 25 any < For SMTP>
Router(config)#access-list 100 permit tcp host 202.129.49.197 eq 110 any < For pop3>
Router(config)#access-list 100 permit tcp host 202.129.49.197 eq 143 any < For imap>
Router(config)#access-list 100 deny ip any any

Router(config)#int f0
Router(config-if)#ip access-group 100 in
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