CCNP Switch Lab 6-3 Securing VLANs with Private VLANs, RACLs, and VACLs

CCNP Switch Lab 6-3 Securing VLANs with Private VLANs, RACLs, and VACLs

Topology

ccnp-switch-lab-securing-vlans-private-vlans-racls-vacls

Objectives

  • Secure the server farm using private VLANs.
  • Secure the staff VLAN from the student VLAN.
  • Secure the staff VLAN when temporary staff personnel are used.

Background
In this lab, you will configure the network to protect the VLANs using router ACLs, VLAN ACLs, and private VLANs. First, you will secure the new server farm by using private VLANs so that broadcasts on one server VLAN are not heard by the other server VLAN. Service providers use private VLANs to separate different customers’ traffic while utilizing the same parent VLAN for all server traffic. The private VLANs provide traffic isolation between devices, even though they might exist on the same VLAN.

You will then secure the staff VLAN from the student VLAN by using a RACL, which prevents traffic from the student VLAN from reaching the staff VLAN. This allows the student traffic to utilize the network and Internet services while keeping the students from accessing any of the staff resources. Lastly, you will configure a VACL that allows a host on the staff network to be set up to use the VLAN for access but keeps the host isolated from the rest of the staff machines. This machine is used by temporary staff employees.

Note: This lab uses Cisco WS-C2960-24TT-L switches with the Cisco IOS image c2960-lanbasek9-mz.122- 46.SE.bin, and Catalyst 3560-24PS switches with the Cisco IOS image c3560-advipservicesk9-mz.122- 46.SE.bin. You can use other switches (such as 2950 or 3550) and Cisco IOS Software versions if they have comparable capabilities and features. Depending on the switch model and Cisco IOS Software version, the commands available and output produced might vary from what is shown in this lab.

Required Resources

  • 2 switches (Cisco 2960 with the Cisco IOS Release 12.2(46)SE C2960-LANBASEK9-M image or comparable)
  • 2 switches (Cisco 3560 with the Cisco IOS Release 12.2(46)SE C3560- ADVIPSERVICESK9-mz image or comparable)
  • 2 PCs (Windows OS) PC-A and PC-B (plus an optional PC for testing, if available)
  • Ethernet and console cables

Step 1: Load and verify the configurations from lab 6-2.

a. Verify that the configurations from Lab 6-2 are loaded on the devices by issuing the show vtp status command. The output should show that the current VTP domain is SWPOD, and VLANs 100 and 200 should be represented in the number of existing VLANs. The output from switch ALS1 is shown as an example. If the switches are not configured properly, erase the startup config, delete the vlan.dat file, and load the configurations saved at the end of lab 6-2.

Note: If you are loading the configurations from Lab 6-2, they do not include VLAN and VTP commands. You must first configure ALS1 and ALS2 as VTP clients and then create VLANs 100 (staff) and 200 (student) and the VTP domain name on DLS1. Refer to Lab 6-1 for assistance if necessary.

Will VLAN information be stored in NVRAM when this device is rebooted? Explain.
No, because this device is in client mode.

b. Issue the show vlan command on DLS1. The student and staff VLANs should be listed in the output of this command.
ccnp-switch-lab-securing-vlans-private-vlans-racls-vacls-1b

How many of these VLANs are present by default?
There should be five VLANs by default.

c. Issue the show interfaces trunk command on each switch. If trunking was configured properly in Labs 6- 1 and 6-2, Fast Ethernet 0/7–0/12 should be in trunking mode on all switches.
ccnp-switch-lab-securing-vlans-private-vlans-racls-vacls-1c

What is the native VLAN for these trunk ports?
The default native VLAN is VLAN 1 .

Note: You can change the native VLAN to something other than VLAN 1 on trunk ports using the switchport trunk native vlan vlan-id command in interface configuration mode. Changing the native VLAN for trunk ports to an unused VLAN can help prevent VLAN hopping attacks. The unused VLAN (for example, VLAN 999) must exist on each switch and be specified on the trunked switch ports.

d. Issue the show standby brief command on DLS2.

For which VLANs is DLS2 the active router?
DLS2 is the active router for VLAN 200.

What is the priority of the current root bridge for VLAN 200?
Based on the output of the show spanning-tree command, the priority is 24776.

Step 2: Configure private VLANs.

Within the server farm VLAN, all servers should be allowed access to the router or gateway but not be able to listen to each other’s broadcast traffic. Private VLANs solve this problem. When you use a private VLAN, the primary VLAN (normal VLAN) can be logically associated with unidirectional, or secondary, VLANs. Servers or hosts in the secondary VLANs can communicate with the primary VLAN but not with another secondary VLAN. You can define the secondary VLANs as either isolated or community.

Stations attached to a port in a secondary VLAN can communicate with trunk ports and promiscuous ports associated with the appropriate primary VLAN. A host on an isolated secondary VLAN can communicate with the primary VLAN (for example, the default gateway SVI), but not hosts in any other secondary VLAN. In addition, the host associated with the isolated port cannot communicate with any other device on the same isolated secondary VLAN. It is essentially isolated from everything except the primary VLAN.

Hosts on ports in a community VLAN cannot communicate with hosts in other secondary VLANs. However, hosts on ports in this type of private VLAN can communicate with hosts on other ports within the community. This lets you have workgroups within an organization while keeping them isolated from each other.

a. The first step is to configure the switches for the primary VLAN. Based on the topology diagram, VLAN 150 will be used for the new server farm. On VTP server DLS1, add VLAN 150, name the VLAN serverfarm and exit vlan config mode.

b. Add HSRP information for the new VLAN on DLS1 and DLS2. Make DLS2 the primary router, and make

c. Verify the HSRP configuration for VLAN 150 using the show standby vlan 150 brief command on DLS2.

d. Set up the primary and secondary private VLAN (PVLAN) information on DLS1 and DLS2. Configure both switches in transparent mode for VTP using the vtp mode transparent global configuration command.

Note: To define PVLANs on DLS1 and DLS2, it is necessary for the switch VTP mode to be set to transparent.

e. Configure DLS1 and DLS2 to contain the new PVLANs. Secondary PVLAN 151 is an isolated VLAN used for Fast Ethernet port 0/6, while secondary PVLAN 152 is used as a community PVLAN for Fast Ethernet ports 0/18–0/20. Configure these new PVLANs in global configuration mode. You also need to associate these secondary VLANs with primary VLAN 150.

f. The private-vlan mapping interface configuration command permits PVLAN traffic to be switched through Layer 3. Configure this command for interface VLAN 150 on DLS1 and DLS2.

g. Verify the creation of the secondary PVLANs and their association with the primary VLAN using the show vlan private-vlan command. Note that no ports are currently associated with these VLANs. This is expected behavior.

Will hosts assigned to ports on private VLAN 151 be able to communicate directly with each other?
No. In an isolated VLAN, all ports can communicate only with ports in the primary VLAN and not each other.

h. On DLS2, configure the Fast Ethernet ports that are associated with the server farm private VLANs. Fast Ethernet port 0/6 is used for the secondary isolated PVLAN 151, and ports 0/18–0/20 are used for the secondary community VLAN 152. The switchport mode private-vlan host command sets the mode on the interface and the switchport private-vlan host-association primary-vlan-id secondary-vlan-id command assigns the appropriate VLANs to the interface. The following commands configure the

As servers are added to Fast Ethernet 0/18–20, will these servers be allowed to hear broadcasts from

each other? Explain.
Yes, because the servers will be in the same community VLAN.

i. Use the show vlan private-vlan command and note that the ports configured are currently associated with these VLANs.

j. Configure host PC-A on DLS2 port Fa0/6 with an IP address in VLAN 150 (for example: 172.16.150.6/24). Use the VLAN 150 HSRP address (172.16.150.1) as the default gateway. This PC represents a server in isolated PVLAN 151.

k. (optional) If you have two additional PCs, attach one to DLS2 port Fa0/18 and the other to port Fa0/19 in the community PVLAN 152. Configure each host with an IP address in VLAN 150 (for example: 172.16.150.18/24 and 172.16.150.19/24). Use the VLAN 150 HSRP address (172.16.150.1) as the default gateway.

l. From PC-A in isolated PVLAN 151 on DLS2 ping the primary VLAN 150 default gateway HSRP virtual IP address 172.16.150.1 and other IP addresses in the network, including PC-B if connected to DLS2 port

Fa0/18 in PVLAN 152. Which pings should succeed and which should fail?
The pings from PC-A in isolated PVLAN 151 to the VLAN 150 default gateway and all other VLAN SVI addresses on DLS1 and DLS2 are successful. If there are multiple hosts in the isolated VLAN, pings between the hosts in the isolated PVLAN fail. If there are multiple hosts in the community PVLAN, the hosts in the community VLAN can ping each other. The pings from the community VLAN to the isolated VLAN, or vice versa, fail. Pings from either the community VLAN or the isolated VLAN to the primary VLAN are successful.

Step 3: Configure RACLs between VLANs.

Configure router access control lists (RACLs) to separate the student and staff VLANs. The staff VLAN (100) can access the student VLAN (200), but the student VLAN does not have access to the staff VLAN for security purposes.

a. To deny the student subnet, use an extended IP access list on DLS1 and DLS2, and assign the access list to the appropriate VLAN interfaces using the ip access-group acl-num {in | out} command.

b. Check the configuration using the show ip access-list and show ip interface vlan vlan-id commands.

c. After the access list has been applied verify the configuration in one of the following ways. Option 1 using real hosts is preferred.

Option 1 : Connect host PC-A to ALS1 port Fa0/15 in staff VLAN 100 and assign it IP address 172.16.100.15/24 with default gateway 172.16.100.1. Connect host PC-B to ALS2 port Fa0/15 in student VLAN 200 and assign it IP address 172.16.200.15/24 with default gateway 172.16.200.1. Ping the staff host from the student host. This ping should fail. Then ping the student host from the staff host. This ping should succeed.

Option 2: On ALS1 set up a simulated host in VLAN 100 and one in VLAN 200 by creating a VLAN 100 and 200 interface on the switch. Give the VLAN 100 interface an IP address in VLAN 100. Give the VLAN 200 interface an IP address in VLAN 200. The following is a sample configuration on ALS1.

d. Ping the interface of the gateway for the staff VLAN (172.16.100.1) with a source of staff VLAN 100 (172.16.100.100) and then ping with a source of student VLAN 200. The pings from the student VLAN should fail.

What does a U signify in the output of the ping command?
The U signifies unreachable. This means that when the ping was getting routed, there was some point where a router did not have a route to the destination or that the packets were getting dropped (for example, through an access list).

Step 4: Configure VACLs.
Configure the network so that the temporary staff host cannot access the rest of the staff VLAN, yet still be able to use the default gateway of the staff subnet to connect to the rest of the network and the ISP. You can accomplish this task by using a VLAN ACL (VACL). Because the temporary staff PC is located on DLS1 Fast Ethernet 0/3, the VACL must be placed on DLS1.

a. Configure an access list on DLS1 called temp-host using the ip access-list extended name command. This list defines the traffic between the host and the rest of the network. Then define the traffic using the permit ip host ip-address subnet wildcard-mask command.

b. The VACL is defined using a VLAN access map. Access maps are evaluated in a numbered sequence. To set up an access map, use the vlan access-map map-name seq# command. The following configuration defines an access map named block-temp, which uses the match statement to match the traffic defined in the access list and denies that traffic. You also need to add a line to the access map that allows all other traffic. If this line is not added, an implicit deny catches all other traffic and denies it.

c. Define which VLANs the access map should be applied to using the vlan filter map-name vlan-list vlanID command.

d. Verify the VACL configuration using the show vlan access-map command on DLS1.

e. (Optional) If possible, connect a PC to the Fast Ethernet 0/3 port of DLS1 and assign the host an IP address of 172.16.100.150/24. Configure the Fast Ethernet 0/3 port as an access port in VLAN 100. Try to ping to another staff host. The ping should not be successful.

Device Configurations (Instructor version)

Switch DLS1

Switch DLS2

Switch ALS1

Switch ALS2

More Resources

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