CCNA RSE Lab: 8.2.3.5 Configuring Stateless and Stateful DHCPv6

CCNA RSE Lab: 8.2.3.5 Configuring Stateless and Stateful DHCPv6

Topology
ccna-rse-lab-configuring-stateless-stateful-dhcpv6-top

Addressing Table

Device Interface IPv6 Address   Prefix Length Default Gateway
R1 G0/1 2001:DB8:ACAD:A::1 64 N/A
S1 VLAN 1 Assigned by SLAAC 64 Assigned by SLAAC
PC-A NIC Assigned by SLAAC and DHCPv6 64 Assigned by R1

Objectives
Part 1: Build the Network and Configure Basic Device Settings
Part 2: Configure the Network for SLAAC
Part 3: Configure the Network for Stateless DHCPv6
Part 4: Configure the Network for Stateful DHCPv6

Background / Scenario
The dynamic assignment of IPv6 global unicast addresses can be configured in three ways:

  • Stateless Address Autoconfiguration (SLAAC) only
  • Stateless Dynamic Host Configuration Protocol for IPv6 (DHCPv6)
  • Stateful DHCPv6

With SLAAC (pronounced slack), a DHCPv6 server is not needed for hosts to acquire IPv6 addresses. It can be used to receive additional information that the host needs, such as the domain name and the domain name server (DNS) address. When SLAAC is used to assign the IPv6 host addresses and DHCPv6 is used to assign other network parameters, it is called Stateless DHCPv6.

With Stateful DHCPv6, the DHCP server assigns all information, including the host IPv6 address. Determination of how hosts obtain their dynamic IPv6 addressing information is dependent on flag settings contained within the router advertisement (RA) messages.

In this lab, you will initially configure the network to use SLAAC. After connectivity has been verified, you will configure DHCPv6 settings and change the network to use Stateless DHCPv6. After verification that Stateless DHCPv6 is functioning correctly, you will change the configuration on R1 to use Stateful DHCPv6. Wireshark will be used on PC-A to verify all three dynamic network configurations.

Note: The routers used with CCNA hands-on labs are Cisco 1 941 Integrated Services Routers (ISRs) with Cisco IOS Release 1 5.2(4)M3 (universalk9 image). The switches used are Cisco Catalyst 2960s with Cisco IOS Release 1 5.0(2) (lanbasek9 image). Other routers, switches and Cisco IOS versions can be used. Depending on the model and Cisco IOS version, the commands available and output produced might vary from what is shown in the labs. Refer to the Router Interface Summary Table at the end of this lab for the correct interface identifiers.

Note: Make sure that the router and switch have been erased and have no startup configurations. If you are unsure, contact your instructor.

Instructor Note: Refer to the Instructor Lab Manual for the procedures to initialize and reload devices.

Note: The default bias template (used by the Switch Database Manager (SDM)) does not provide IPv6 address capabilities. Verify that SDM is using either the dual-ipv4-and-ipv6 template or the lanbase-routing template. The new template will be used after reboot even if the config is not saved.

Required Resources

  • 1 Router (Cisco 1941 with Cisco IOS Release 15.2(4)M3 universal image or comparable)
  • 1 Switch (Cisco 2960 with Cisco IOS Release 15.0(2) lanbasek9 image or comparable)
  • 1 PC (Windows 7 or Vista with Wireshark and terminal emulation program, such as Tera Term)
  • Console cables to configure the Cisco IOS devices via the console ports
  • Ethernet cables as shown in the topology

Instructor Note: Wireshark needs to be preinstalled on PC-A.

Note: DHCPv6 client services are disabled on Windows XP. It is recommended to use a Windows 7 host for this lab.

Part 1: Build the Network and Configure Basic Device Settings

In Part 1 , you will set up the network topology and configure basic settings, such as device names, passwords and interface IP addresses.

Step 1: Cable the network as shown in the topology.
Step 2: Initialize and reload the router and switch as necessary.
Step 3: Configure R1 .
a. Console into R1 and enter global configuration mode.
b. Copy the following basic configuration and paste it to the running-configuration on R1.

c. Save the running configuration to the startup configuration.

Step 4: Configure S1 .
a. Console into S1 and enter global configuration mode.
b. Copy the following basic configuration and paste it to the running-configuration on S1.

c. Administratively disable all inactive interfaces.
d. Save running configuration to the startup configuration.

Part 2: Configure the Network for SLAAC

Step 1: Prepare PC-A.
a. Verify that the IPv6 protocol has been enabled on the Local Area Connection Properties window. If the Internet Protocol Version 6 (TCP/IPv6) check box is not checked, click to enable it.

ccna-rse-lab-configuring-stateless-stateful-dhcpv6-1

b. Start a Wireshark capture of traffic on the NIC.
c. Filter the data capture to see only RA messages. This can be done by filtering on IPv6 packets with a destination address of FF02::1, which is the all-unicast client group address. The filter entry used with Wireshark is ipv6.dst==ff02::1 , as shown here.

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Step 2: Configure R1 .
a. Enable IPv6 unicast routing.
b. Assign the IPv6 unicast address to interface G0/1 according to the Addressing Table.
c. Assign FE80::1 as the IPv6 link-local address for interface G0/1.
d. Activate interface G0/1.

Step 3: Verify that R1 is part of the all-router multicast group.
Use the show ipv6 interface g0/1 command to verify that G0/1 is part of the All-router multicast group
(FF02::2). RA messages are not sent out G0/1 without that group assignment.

Step 4: Configure S1.
Use the ipv6 address autoconfig command on VLAN 1 to obtain an IPv6 address through SLAAC.

Step 5: Verify that SLAAC provided a unicast address to S1.
Use the show ipv6 interface command to verify that SLAAC provided a unicast address to VLAN1 on S1.

Step 6: Verify that SLAAC provided IPv6 address information on PC-A.
a. From a command prompt on PC-A, issue the ipconfig /all command. Verify that PC-A is showing an IPv6 address with the 2001:db8:acad:a::/64 prefix. The Default Gateway should have the FE80::1 address.

ccna-rse-lab-configuring-stateless-stateful-dhcpv6-3

b. From Wireshark, look at one of the RA messages that were captured. Expand the Internet Control Message Protocol v6 layer to view the Flags and Prefix information. The first two flags control DHCPv6 usage and are not set if DHCPv6 is not configured. The prefix information is also contained within this RA message.
ccna-rse-lab-configuring-stateless-stateful-dhcpv6-4

Part 3: Configure the Network for Stateless DHCPv6

Step 1: Configure an IPv6 DHCP server on R1.
a. Create an IPv6 DHCP pool.

b. Assign a domain name to the pool.

c. Assign a DNS server address.

d. Assign the DHCPv6 pool to the interface.

e. Set the DHCPv6 network discovery (ND) other-config-flag.

Step 2: Verify DHCPv6 settings on interface G0/1 on R1 .
Use the show ipv6 interface g0/1 command to verify that the interface is now part of the IPv6 multicast allDHCPv6-servers group (FF02::1:2). The last line of the output from this show command verifies that the other-config-flag has been set.

Step 3: View network changes to PC-A.
Use the ipconfig /all command to review the network changes. Notice that additional information, including the domain name and DNS server information, has been retrieved from the DHCPv6 server. However, the IPv6 global unicast and link-local addresses were obtained previously from SLAAC.
ccna-rse-lab-configuring-stateless-stateful-dhcpv6-5

Step 4: View the RA messages in Wireshark.
Scroll down to the last RA message that is displayed in Wireshark and expand it to view the ICMPv6 flag settings. Notice that the other configuration flag is set to 1.
ccna-rse-lab-configuring-stateless-stateful-dhcpv6-6

Step 5: Verify that PC-A did not obtain its IPv6 address from a DHCPv6 server.
Use the show ipv6 dhcp binding and show ipv6 dhcp pool commands to verify that PC-A did not obtain an IPv6 address from the DHCPv6 pool.

Step 6: Reset PC-A IPv6 network settings.
a. Shut down interface F0/6 on S1.

Note: Shutting down the interface F0/6 prevents PC-A from receiving a new IPv6 address before you reconfigure R1 for Stateful DHCPv6 in Part 4.

b. Stop Wireshark capture of traffic on the PC-A NIC.
c. Reset the IPv6 settings on PC-A to remove the Stateless DHCPv6 settings.

  1. Open the Local Area Connection Properties window, deselect the Internet Protocol Version 6 (TCP/IPv6) check box, and click OK to accept the change.
  2. Open the Local Area Connection Properties window again. Click to enable the Internet Protocol Version 6 (TCP/IPv6) check box, and then click OK to accept the change.

 

Part 4: Configure the Network for Stateful DHCPv6

Step 1: Prepare PC-A.
a. Start a Wireshark capture of traffic on the NIC.
b. Filter the data capture to see only RA messages. This can be done by filtering on IPv6 packets with a destination address of FF02::1, which is the all-unicast client group address.

ccna-rse-lab-configuring-stateless-stateful-dhcpv6-7

Step 2: Change the DHCPv6 pool on R1 .
a. Add the network prefix to the pool.

b. Change the domain name to ccna-statefulDHCPv6.com.

Note: You must remove the old domain name. It is not replaced by the domain-name command.

c. Verify DHCPv6 pool settings.

d. Enter debug mode to verify the Stateful DHCPv6 address assignment.

Step 3: Set the flag on G0/1 for Stateful DHCPv6.

Note: Shutting down the G0/1 interface before making changes ensures that an RA message is sent when the interface is activated.

Step 4: Enable interface F0/6 on S1.
Now that R1 has been configured for Stateful DHCPv6, you can reconnect PC-A to the network by activating interface F0/6 on S1.

Step 5: Verify Stateful DHCPv6 settings on R1 .
a. Issue the show ipv6 interface g0/1 command to verify that the interface is in Stateful DHCPv6 mode.

b. In a command prompt on PC-A, type ipconfig /release6 to release the currently assigned IPv6 address. Then type ipconfig /renew6 to request an IPv6 address from the DHCPv6 server.

c. Issue the show ipv6 dhcp pool command to verify the number of active clients.

d. Issue the show ipv6 dhcp binding command to verify that PC-A received its IPv6 unicast address from the DHCP pool. Compare the client address to the link-local IPv6 address on PC-A using the ipconfig /all command. Compare the address provided by the show command to the IPv6 address listed with the ipconfig /all command on PC-A.

ccna-rse-lab-configuring-stateless-stateful-dhcpv6-8

e. Issue the undebug all command on R1 to stop debugging DHCPv6.

Note: Typing u all is the shortest form of this command and is useful to know if you are trying to stop debug messages from continually scrolling down your terminal session screen. If multiple debugs are in process, the undebug all command stops all of them.

f. Review the debug messages that appeared on your R1 terminal screen.

Step 6: Verify Stateful DHCPv6 on PC-A
a. Stop the Wireshark capture on PC-A.
b. Expand the most recent RA message listed in Wireshark. Verify that the Managed address configuration flag has been set.
ccna-rse-lab-configuring-stateless-stateful-dhcpv6-9

c. Change the filter in Wireshark to view DHCPv6 packets only by typing dhcpv6, and then Apply the filter. Highlight the last DHCPv6 reply listed and expand the DHCPv6 information. Examine the DHCPv6 network information that is contained in this packet.
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Reflection
1. What IPv6 addressing method uses more memory resources on the router configured as a DHCPv6 server, Stateless DHCPv6 or Stateful DHCPv6? Why?
Stateful DHCPv6 uses more memory resources. Answers will vary, but Stateful DHCPv6 requires the router to store dynamic state information about the DHCPv6 clients. Stateless DHCPv6 clients do not use the DHCP server to obtain address information, so this information does not need to be stored.

2. Which type of dynamic IPv6 address assignment is recommended by Cisco, Stateless DHCPv6 or Stateful DHCPv6?
Cisco recommends Stateless DHCPv6 when implementing and deploying IPv6 networks without a Cisco Network Register (CNR).

Router Interface Summary Table

Router Interface Summary

Router Model Ethernet Interface #1 Ethernet Interface #2 Serial Interface #1 Serial Interface #2
1800 Fast Ethernet 0/0
(F0/0)
Fast Ethernet 0/1
(F0/1)
Serial 0/0/0 (S0/0/0) Serial 0/0/1 (S0/0/1)
1900 Gigabit Ethernet 0/0
(G0/0)
Gigabit Ethernet 0/1
(G0/1)
Serial 0/0/0 (S0/0/0) Serial 0/0/1 (S0/0/1)
2801 Fast Ethernet 0/0
(F0/0)
Fast Ethernet 0/1
(F0/1)
Serial 0/1 /0 (S0/1 /0) Serial 0/1 /1 (S0/1 /1)
2811 Fast Ethernet 0/0
(F0/0)
Fast Ethernet 0/1
(F0/1)
Serial 0/0/0 (S0/0/0) Serial 0/0/1 (S0/0/1)
2900 Gigabit Ethernet 0/0 (G0/0) Gigabit Ethernet 0/1 (G0/1) Serial 0/0/0(S0/0/0) Serial 0/0/1 (S0/0/1)
Note: To find out how the router is configured, look at the interfaces to identify the type of router and how many interfaces the router has. There is no way to effectively list all the combinations of configurations for each router class. This table includes identifiers for the possible combinations of Ethernet and Serial interfaces in the device. The table does not include any other type of interface, even though a specific router may contain one. An example of this might be an ISDN BRI interface. The string in parenthesis is the legal abbreviation that can be used in Cisco IOS commands to represent the interface.

Device Configs – Part 1 and 2 combined for R1 and S1

Router R1 (After parts 1 and 2 of this lab)

Switch S1 (After parts 1 and 2 of this lab)

Router R1 (Final)

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