Lab Objective:
The objective of this lab exercise is to learn how to examine NDP functionality on a Cisco router.
Lab Purpose:
A major difference between Internet Protocol version 4 (IPv4) and Internet Protocol version 6 (IPv6) is how they discover the data link layer address of a host they want to send a packet to. You’ve already learned that IPv4 uses ARP for this purpose, but IPv6 uses NDP.
NDP packets are exchanged by connected links and therefore should be using either a link-local address or a multicast address with a link-local scope. The hop limit is set to 255 to prevent hackers from spoofing or attacking NDP.
Lab Tool:
Packet Tracer.
Lab Topology:
Please use the following topology to complete this lab exercise.
Lab Walkthrough:
Task 1:
Configure a hostname on R1 as illustrated in the topology.
Router#configure terminal
Router(config)#hostname R1
R1(config)#
Task 2:
Enable IPv6 on the router, then auto-configure IPv6 addresses on the Gig0/0/0 interface of R1, as illustrated in the topology.
R1#configure terminal
R1(config)#ipv6 unicast-routing
R1(config)#interface gi0/0/0
R1(config-if)#ipv6 enable
R1(config-if)#no shut
R1#show ipv6 interface brief
GigabitEthernet0/0/0 [up/up]
FE80::201:97FF:FE23:8101
Vlan1 [administratively down/down] Unassigned
Task 3:
On R1, configure a loopback (virtual) interface with an IPv6 address.
R1#configure terminal
R1(config)#interface loopback 0
R1(config-if)#ipv6 address 2001::1/64
R1(config-if)#end
R1#show ipv6 interface brief
GigabitEthernet0/0/0 [up/up]
FE80::201:97FF:FE23:8101
GigabitEthernet0/0/1 [administratively down/down]
unassigned
GigabitEthernet0/0/2 [administratively down/down]
unassigned
Loopback0 [up/up]
FE80::260:47FF:FE62:5043
2001::1
Vlan1 [administratively down/down]
Unassigned
Task 4:
On R1, start debugging for ND (neighbor discovery) messages.
R1#debug ipv6 nd
Task 5:
Next, click on the PC, then under Desktop, click on IP configuration. Select Automatic under IPv6 configuration.
This lab will work perfectly using live equipment, but Packet Tracer can be somewhat flaky. If the above configuration doesn’t work, then you can press the Static radio button and paste in the default gateway, which is the IPv6 address on the G0/0/0 interface. Here is what it looks like for me, but yours will differ.
Task 6:
Ping the R1 loopback address from PC.
Task 7:
Verify the IPv6 neighbor discovery messages under R1.
R1#debug ipv6 nd
ICMP Neighbor Discovery events debugging is on
R1#*Mar 1 05:28:50.047: ICMPv6-ND: Sending NS for FE80::2D0:58FF:FE97:D106 on GigabitEthernet0/0/0
*Mar 1 05:28:50.047: ICMPv6-ND: Received NA for FE80::2D0:58FF:FE97:D106 on GigabitEthernet0/0/0 from FE80::2D0:58FF:FE97:D106
*Mar 1 05:28:51.883: ICMPv6-ND: Request to send RA for FE80::201:97FF:FE23:8101
*Mar 1 05:28:51.883: ICMPv6-ND: Sending RA from FE80::201:97FF:FE23:8101 to FF02::1 on GigabitEthernet0/0/0
R1#show ipv6 neighbors
IPv6 Address Age Link-layer Addr State Interface
FE80::2D0:58FF:FE97:D106 7 00D0.5897.D106 REACH Gig0/0/0
Note:
Packet Tracer is a great tool, but doesn’t always work as expected and may not perform in the same way live equipment does. So, don’t get frustrated.
