Troubleshooting
Verify that SLAAC is Enabled
Command to verify that SLAAC is Enabled
R1# show ipv6 interface G0/0/1 | section Joined
Joined group address(es):
FF02::1
FF02::2
FF02::1:FF00:1
R1#
An IPv6-enabled Cisco router sends RA messages to the IPv6 all-nodes multicast address ff02::1 every 200 seconds.
SLAAC + Stateless DHCPv6 Verification
Command to verify that SLAAC + Stateless DHCPv6 is Enabled
R1# show ipv6 interface g0/0/1 | begin ND ND DAD is enabled, number of DAD attempts: 1 ND reachable time is 30000 milliseconds (using 30000) ND advertised reachable time is 0 (unspecified) ND advertised retransmit interval is 0 (unspecified) ND router advertisements are sent every 200 seconds ND router advertisements live for 1800 seconds ND advertised default router preference is Medium Hosts use stateless autoconfig for addresses. Hosts use DHCP to obtain other configuration. R1#
Stateless DHCPv6 is enabled on a router interface using the ipv6 nd other-config-flag interface configuration command. This sets the O flag to 1.
The highlighted output confirms the RA will tell receiving hosts to use stateless autoconfigure (A flag = 1) and contact a DHCPv6 server to obtain another configuration information (O flag = 1).
DHCPv6 Server Verification Commands
show ipv6 dhcp pool
R1# show ipv6 dhcp pool DHCPv6 pool: LAN-POOL-1 Address allocation prefix: 2001:DB8:ACAD:1::/64 valid 172800 preferred 86400 (2 in use, 0 conflicts) DNS server: 2001:4860:4860::8888 Domain name: example.com Active clients: 2 R1#
The show ipv6 dhcp pool command verifies the name of the DHCPv6 pool and its parameters. The command also identifies the number of active clients. In this example, the LAN-POOL-1 pool currently has 2 clients, which reflects two devices receiving their IPv6 global unicast address from this server.
When a router is providing stateful DHCPv6 services, it also maintains a database of assigned IPv6 addresses.
show ipv6 dhcp binding
R1# show ipv6 dhcp binding
Client: FE80::192F:6FBC:9DB:B749
DUID: 0001000125148183005056B327D6
Username : unassigned
VRF : default
IA NA: IA ID 0x03000C29, T1 43200, T2 69120
Address: 2001:DB8:ACAD:1:A43C:FD28:9D79:9E42
preferred lifetime 86400, valid lifetime 172800
expires at Sep 27 2019 09:10 AM (171192 seconds)
Client: FE80::2FC:BAFF:FE94:29B1
DUID: 0003000100FCBA9429B0
Username : unassigned
VRF : default
IA NA: IA ID 0x00060001, T1 43200, T2 69120
Address: 2001:DB8:ACAD:1:B4CB:25FA:3C9:747C
preferred lifetime 86400, valid lifetime 172800
expires at Sep 27 2019 09:29 AM (172339 seconds)
R1#
Use the show ipv6 dhcp binding command output to display the IPv6 link-local address of the client and the global unicast address assigned by the server.
The output displays the current stateful binding on R1. The first client in the output is PC1 and the second client is R3.
This information is maintained by a stateful DHCPv6 server. A stateless DHCPv6 server would not maintain this information.