5.5.1 Packet Tracer – IPv4 ACL Implementation Challenge (Answers)

5.5.1 Packet Tracer – IPv4 ACL Implementation Challenge (Instructor Version)

Instructor 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.

HQ(config)#access-list 101 deny tcp any host 192.168.1.70 eq ftp
HQ(config)#access-list 101 deny icmp any 192.168.1.0 0.0.0.63
HQ(config)#access-list 101 permit ip any any
HQ(config)#interface Serial0/1/0
HQ(config-if)#ip access-group 101 in

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.

HQ(config)#access-list 111 deny ip any host 192.168.2.45
HQ(config)#access-list 111 permit ip any any
HQ(config)#interface GigabitEthernet0/0/0
HQ(config-if)#ip access-group 111 in

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.

HQ(config)#ip access-list standard vty_block
HQ(config-std-nacl)#permit 192.168.1.64 0.0.0.7
HQ(config-std-nacl)#line vty 0 4
HQ(config-line)#access-class vty_block in

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.

Branch(config)#ip access-list extended branch_to_hq
Branch(config-ext-nacl)#deny ip 192.168.2.0 0.0.0.31 192.168.1.0 0.0.0.63
Branch(config-ext-nacl)#deny ip 192.168.2.32 0.0.0.15 192.168.1.0 0.0.0.63
Branch(config-ext-nacl)#permit ip any any
Branch(config-ext-nacl)#interface Serial0/1/1
Branch(config-if)#ip access-group branch_to_hq out

Step 3: Verify ACL Operation.

a. 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.

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

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.

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

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

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.

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

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

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

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

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

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

Download Packet Tracer Completed File

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