1. Keeping the world safe by preventing your students from accessing it…
A bit of ACL… Special Thanks to Mr. Edd Spidell of Cranston Vocational Technical School for this PPT.
Keeping the world safe by preventing your students from accessing it…

2. What are Access Control Lists?
They are statements used to control the flow of network traffic and provide varying levels of network security.
The lists contain Permit or Deny statements that filter network traffic based on the source address, destination address, and protocol type of a packet.

3. How can we let Jabba
get access to Yoda but
not to the Internet?

4. To prevent Jabba’s access to the Internet, we could:
Put him in CCRI’s new computer wing and watch him try to reach the keyboard….or to get back out…
Have Princess Leah join him for lunch…
Use ACL’s on an interface to limit traffic…
Your final answer is?

5. We would use ACL’s but the others would be fun too…
We would configure the router port that is the gateway for Jabba to prevent access.
SkyWalker#config t
SkyWalker(config)#access-list 1 deny
SkyWalker(config)#access-list 1 permit any
SkyWalker(config)#int e1
SkyWalker(config-if)#ip access-group 1 in
SkyWalker(config-if)#^z
This is a Standard Access List which is
denying packets based on the source address.

6. To remove an ACL, we must go back into the router configuration.
SkyWalker#config t
SkyWalker(config)#no access-list 1
SkyWalker(config)#int e1
SkyWalker(config-if)#no ip access-group 1 in
SkyWalker(config-if)#^Z

7. If we cut a deal with Jabba so he could use the Internet, but prevent him from downloading from FTP sites, we can use Extended Access Control Lists
Unlike standard lists, the EACL’s can filter by source IP, destination IP, protocol type,and application port number. For this instance, we will be using Port 21 (FTP).

8. To block Jabba’s FTP access…
SkyWalker#config t
SkyWalker(config)#access-list 100 deny tcp eq 21
SkyWalker(config)#access-list 100 permit ip any any
SkyWalker(config)#int e1
SkyWalker(config-if)#ip access-group 100 in
SkyWalker(config-if)#^Z

9. To remove the EACL… SkyWalker#config t
SkyWalker(config)#no access-list 100
SkyWalker(config)#int e1
SkyWalker(config-if)#no ip access-group 100 in
SkyWalker(config-if)#^Z

10. Wildcard Masks
Routers use them to determine which bits in an address are significant.
0’s(zeros) are significant, 1’s(ones) are not.
For example:
The makes the access list match to the host (Jabba’s) exactly.
Another example:
The makes the access list apply to both Yoda and Jabba on the .20 subnet.

11. You know there is much more to be learned…
Due to time constraints and my limited knowledge on this subject, I defer to those of you that have a better understanding of what I have tried to present.
In summary, my opinion is that this subject is probably the most important part of the entire curriculum so far, and at the same time, the most involved from a learning standpoint.