The document discusses access control lists (ACLs) including: 1. Common port numbers for protocols like SMTP, POP3, IMAP, HTTP, HTTPS, DNS, FTP, TFTP, SNMP, and NTP. 2. The basics of packet filtering using ACLs including allowing or denying based on source/destination IP addresses and ports. 3. Numbering, naming, and applying standard and extended ACLs to interfaces for inbound and outbound traffic.

1. Access Control List
2009 © Alexander Rybolovlev

2. A TCP Conversation
SMTP 25
POP3 110
IMAP 143
HTTP 80
HTTPS 443
DNS 53
FTP-DATA 20
FTP 21
TFTP 69
SNMP 169
NTP 123

3. Packet Filtering
ALLOW or DENY
•Source IP address
•Destination IP address
•ICMP message type
•TCP/UDP source port
•TCP/UDP destination port
One ACL per protocol (e.g., IP or IPX)
One ACL per interface (e.g., FastEthernet0/0)
One ACL per direction (i.e., IN or OUT)
IN
OUT

4. Numbering and Naming ACLs
Router(config)#access-list ?
<1-99>
<100-199>
IP standard access list
IP extended access list
<1100-1199> Extended 48-bit MAC address access list
<1300-1999> IP standard access list (expanded range)
<200-299> Protocol type-code access list
<2000-2699> IP extended access list (expanded range)
<700-799> 48-bit MAC address access list
You assign a number based on which protocol you want filtered:
•(1 to 99) and (1300 to 1999): Standard IP ACL
•(100 to 199) and (2000 to 2699): Extended IP ACL
You assign a name by providing the name of the ACL:
•Names can contain alphanumeric characters.
•It is suggested that the name be written in CAPITAL LETTERS.
•Names cannot contain spaces or punctuation and must begin with a letter.
•You can add or delete entries within the ACL.

5. Where To Place ACLs
Router1 Router2
Host2
Host1 Host3
Fa0/1Fa0/1
Router0
Standart ACLExtended ACL
192.168.2.0/24
192.168.2.0/24

6. Standard ACL
[no] access-list acl-num {deny|permit|remark} [source [source-wildcard]] [log]
Router#show access-lists
Standard IP access list 99
10 permit host 192.168.99.0
20 permit host 192.168.98.0
Router#conf t
Router(config)#no access-list 99
Router(config)#end
Router#show access-lists
Router#
Router(config)#access-list 10 remark Acces_to_LAN
Router(config)#access-list 10 permit 192.168.10.0
access-list 2 deny 192.168.10.1
access-list 2 permit 192.168.10.0 0.0.0.255
access-list 2 deny 192.168.0.0 0.0.255.255
access-list 2 permit 192.0.0.0 0.255.255.255
Router(config-if)#ip access-group {access-list-number | access-list-name} {in | out}
Router(config)#access-list 1 permit ip 192.168.10.0 0.0.0.255
Router(config)#interface FastEthernet0/0
Router(config-if)#ip access-group 1 out

7. Example

8. Example

9. Example

10. Example

11. Edit Standard ACL
#1
R1#show running-config | include access-list
access-list 20 permit 192.168.10.100
access-list 20 deny 192.168.10.0 0.0.0.255
#2
access-list 20 permit 192.168.10.11
access-list 20 deny 192.168.10.0 0.0.0.255
#3
R1#conf t
R1(config)#no access-list 20
R1(config)#access-list 20 remark Access for permit host 10.11
R1(config)#access-list 20 permit 192.168.10.11
R1(config)#access-list 20 deny 192.168.10.0 0.0.0.255

12. Naming ACL
Router(config)#ip access-list [standart | extended] name
Router(config-std-nacl)#[no] [num] {deny|permit|remark} …
Router(config)#ip access-list standard Bumburum
Router(config-std-nacl)#deny host 192.168.0.1
Router(config-std-nacl)#permit 192.168.0.0 0.0.0.255
Router#sh access-lists
Standard IP access list Bumburum
10 deny host 192.168.0.1
20 permit 192.168.0.0 0.0.0.255
Router(config-if)#ip access-group {access-list-number | access-list-name} {in | out}
Router(config-if)#ip access-group Bumburum out

13. Edit ACL
Router#show access-lists {acl-num|name}
Router#sh access-lists 99
Standard IP access list 99
10 permit host 192.168.9.9
20 permit host 192.168.9.11
Router(config)#ip access-list {standart | extended} {acl-num|name}
Router(config-std-nacl)#[no] [num] {deny|permit|remark} …
Router#sh access-lists standard 99
Router(config-std-nacl)#15 permit host 192.168.9.10
Router#sh access-lists 99
Standard IP access list 99
10 permit host 192.168.9.9
15 permit host 192.168.9.10
20 permit host 192.168.9.11

14. Extended ACL
R1(config)#access-list 101 permit tcp any eq ?

15. Example

16. Example

17. Example

18. Difference between STD and EXT ACL
STANDARD EXTENDED
The access-list number range from1 to 99 The access-list number range from100 to
199
Can block a host, network and subnet Can block a host, network ,subnet and
service
Two way communication is stopped One way communication is stopped
Implemented closest to the destination Implemented closest to the source
Filtering is done based on only source IP
address
Checks source,destination,protocol,
port no.

19. 1. Create access list (std or extnd)
2. Apply access-list to an interface(inbound/outbound)
R0(config)#access-list 1 deny 192.168.2.101 0.0.0.0
R0(config)#access-list 1 permit any
R0(config)#int gi0/0
R0(config)#ip access-group 1 out

20. R0(config)#no access-list 1
R0(config)#access-list 2 deny 192.168.2.100
R0(config)#access-list 2 deny 192.168.2.101
R0(config)#access-list 2 permit any
R0(config)#int gi0/0
R0(config)#no ip access-group 1 out
R0(config)# ip access-group 2 out
R0(config)#no access-list 2
R0(config)#access-list 3 deny 192.168.2.0 0.0.0.255
R0(config)#int gi0/0
R0(config)#no ip access-group 2 out
R0(config)# ip access-group 3 out

21. EXTENDED ACL

22. R0(config)#access-list 100 deny tcp host 192.168.1.10 host 192.168.4.100 eq www
R0(config)#access-list 100 deny tcp host 192.168.1.11 host 192.168.4.100 eq ftp
R0(config)#access-list 100 deny icmp host 192.168.1.12 host 192.168.4.100
R0(config)#access-list 100 permit ip any any
R0(config)# int se0/0/0
R0(config-if)# ip access-group 100 out
R0# show access-list
source server