5.5.1 Packet Tracer – IPv4 ACL Implementation Challenge Answers

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Answers Note: Red font color or gray highlights indicate text that appears in the instructor copy only.

Addressing Table

Objectives

• Configure a router with standard named ACLs.
• Configure a router with extended named ACLs.
• Configure a router with extended ACLs to meet specific communication requirements.
• Configure an ACL to control access to network device terminal lines.
• Configure the appropriate router interfaces with ACLs in the appropriate direction.
• Verify the operation of the configured ACLs.

Background / Scenario

In this activity you will configure extended, standard named, and extended named ACLs to meet specified communication requirements.

Instructions

Step 1:  Verify Connectivity in the New Company Network

First, test connectivity on the network as it is before configuring the ACLs. All hosts should be able to ping all other hosts.

Step 2:  Configure Standard and Extended ACLs per Requirements.

Configure ACLs to meet the following requirements:

Important guidelines:

• Do not use explicit deny any statements at the end of your ACLs.
• Use shorthand (host and any) whenever possible.
• Write your ACL statements to address the requirements in the order that they are specified here.
• Place your ACLs in the most efficient location and direction.

ACL 1 Requirements

• Create ACL 101.
• Explicitly block FTP access to the Enterprise Web Server from the internet.
• No ICMP traffic from the internet should be allowed to any hosts on HQ LAN 1
• Allow all other traffic.

ACL 2 Requirements

• Use ACL number 111
• No hosts on HQ LAN 1 should be able to access the Branch Server.
• All other traffic should be permitted.

ACL 3: Requirements

• Create a named standard ACL. Use the name vty_block. The name of your ACL must match this name exactly.
• Only addresses from the HQ LAN 2 network should be able to access the VTY lines of the HQ router.

ACL 4: Requirements

• Create a named extended ACL called branch_to_hq. The name of your ACL must match this name exactly.
• No hosts on either of the Branch LANs should be allowed to access HQ LAN 1. Use one access list statement for each of the Branch LANs.
• All other traffic should be allowed.

Step 3:  Verify ACL Operation.

1. Perform the following connectivity tests between devices in the topology. Note whether or not they are successful.

Note: Use the show ip access-lists command to verify ACL operation. Use the clear access list counters command to reset the match counters.

Questions:

Send a ping request from Branch PC to the Enterprise Web Server. Was it successful? Explain.

Type your answers here.

The ping was successful because it was permitted by the ACL.

Which ACL statement permitted or denied the ping between these two devices? List the access list name or number, the router on which it was applied, and the specific line that the traffic matched.

Type your answers here.

The last line in the branch_to_hq ACL on the Branch Router is permit ip any.

Attempt to ping from PC-1 on the HQ LAN 1 to the Branch Server. Was it successful? Explain.

Type your answers here.

The ping was not successful because the traffic was blocked by an access list.

Which ACL statement permitted or denied the ping between these two devices?

Type your answers here.

Statement 10 in access list 111 on the HQ router denies all traffic to the branch server.

Open a web browser on the External Server and attempt to bring up a web page stored on the Enterprise Web Server. Is it successful? Explain.

Type your answers here.

Yes, the External Server can access a web page on the Enterprise Web Server.  HTTP traffic is not blocked to the Enterprise Web Server.

Which ACL statement permitted or denied the ping between these two devices?

Type your answers here.

Line 20 in access list 101 on the HQ router permitted this traffic.

2. Test connections to an internal server from the internet.

Questions:

From the command line on the Internet User PC, attempt to make an FTP connection to the Branch Server. Is the FTP connection successful?

Type your answers here.

Yes, the FTP connection from the internet User PC to the Branch Server is successful. 

Which access list should be modified to prevent users from the Internet to make FTP connections to the Branch Server?

Type your answers here.

The access list 101 on the HQ router needs to be modified to deny this traffic.

Which statement(s) should be added to the access list to deny this traffic?

Type your answers here.

The statement “deny tcp any host 192.168.2.45 eq 21” or “deny tcp any host 192.168.2.45 range 20 21” needs to be added to the access list 101.

End of document

Answer Scripts

Router HQ

enable

conf t

access-list 101 deny tcp any host 192.168.1.70 eq ftp

access-list 101 deny icmp any 192.168.1.0 0.0.0.63

access-list 101 permit ip any any

ip access-list standard vty_block

 permit 192.168.1.64 0.0.0.7

access-list 111 deny ip any host 192.168.2.45

access-list 111 permit ip any any

interface GigabitEthernet0/0/0

 ip access-group 111 in

interface Serial0/1/0

 ip access-group 101 in

line vty 0 4

 access-class vty_block in

end

Router Branch

enable

conf t

ip access-list extended branch_to_hq

 deny ip 192.168.2.0 0.0.0.31 192.168.1.0 0.0.0.63

 deny ip 192.168.2.32 0.0.0.15 192.168.1.0 0.0.0.63

 permit ip any any

interface Serial0/1/1

 ip access-group branch_to_hq out

end

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