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Global ConfigDomain 7.0
ipv6 unicast-routing
The mandatory master command required to unlock IPv6 capabilities on a Cisco device. By default, Cisco routers have Layer 3 forwarding enabled for IPv4, but completely disabled for IPv6. This command turns on the IPv6 routing engine and allows the router to generate ICMPv6 Router Advertisements.
Quick Reference
Execution Mode
Router(config)#Impact on DefaultsActivates IPv6 RIB / Forwarding
Prerequisite ForOSPFv3, IPv6 Static Routes, and Client SLAAC
Negation Command
no ipv6 unicast-routingCCNA Exam Gotchas
[!]
The Ghost Interface Trap
If you navigate to an interface and assign a static address like ipv6 address 2001:db8::1/64, the interface will come up and you can ping locally connected neighbors. However, if you forget to issue the global ipv6 unicast-routing command, the router will act purely as an IPv6 endpoint host, completely refusing to forward transit packets between different interfaces. Always verify this command is running first during troubleshooting simulations.