Lab Objective
Configure one router to advertise an IPv6 prefix, then configure a second router to automatically generate its own global unicast address from that prefix using SLAAC, and verify the resulting address.
Lab Purpose
Manually typing a full IPv6 address on every device does not scale any better than manually configuring IPv4, discussed in an earlier lab. SLAAC allows a device to construct its own address automatically from network-provided information, a mechanism engineers must understand both to configure and to explain unexpected addresses appearing on client devices.
Lab Topology
Two routers connected via a GigabitEthernet link:
R1 (advertises prefix) ---- Gi0/0 ---- Gi0/0 ---- R2 (autoconfigures)
R1's Gi0/0: 2001:DB8:B:1::1/64 (manually configured)
R2's Gi0/0: address to be generated automaticallyTask 1: Configure R1 with a Manual Address
Enable IPv6 routing on R1 and manually assign 2001:DB8:B:1::1/64 to its Gi0/0 interface, as covered in the previous IPv6 addressing lab.
Task 2: Configure R2 to Use SLAAC
Enable IPv6 routing on R2 and configure its Gi0/0 interface to automatically generate its own address based on router advertisements received from R1, rather than typing a specific address.
Task 3: Verify the Autoconfigured Address
Display R2's Gi0/0 interface and identify the automatically generated global unicast address, noting how it relates to the prefix advertised by R1 and R2's own interface identifier.
Task 4: Verify Connectivity
Confirm R2 can ping R1 using its newly autoconfigured address.
Solution and Verification
R1(config)# ipv6 unicast-routing
R1(config)# interface gigabitethernet0/0
R1(config-if)# ipv6 address 2001:DB8:B:1::1/64
R1(config-if)# no shutdownR2(config)# ipv6 unicast-routing
R2(config)# interface gigabitethernet0/0
R2(config-if)# ipv6 address autoconfig
R2(config-if)# no shutdownR2# show ipv6 interface gigabitethernet0/0
GigabitEthernet0/0 is up, line protocol is up
IPv6 is enabled, link-local address is FE80::250:56FF:FECC:5566
Global unicast address(es):
2001:DB8:B:1:250:56FF:FECC:5566, subnet is 2001:DB8:B:1::/64 [AUT]
-- The prefix 2001:DB8:B:1::/64 came from R1's
-- router advertisement, while the host portion
-- (250:56FF:FECC:5566) was derived from R2's
-- own interface MAC address using the EUI-64
-- process -- the [AUT] tag confirms this
-- address was autoconfigured rather than
-- manually enteredR2# ping 2001:DB8:B:1::1
!!!!!
Success rate is 100 percent (5/5)Key Takeaway
SLAAC combines a network-supplied prefix (learned from a router advertisement) with a device-generated interface identifier to build a complete global unicast address automatically. The [AUT] flag in show ipv6 interface output is the definitive way to confirm whether an address was learned this way versus manually configured.