IPv6 troubleshooting
IPv6 was rolled out last night and nothing works: the PCs show only fe80:: addresses. The plan was Gi0/0 = 2001:db8:acad:10::1/64 and Gi0/1 = 2001:db8:acad:20::1/64, with the PCs using SLAAC. Find and fix every fault on R1 so that PC1 and PC2 get global addresses and can reach each other's LAN.
How it works: this is VulnTech NetLab, a network simulator running in your browser. Click a device in the diagram to open its console and type commands, just like on real equipment (? shows help, Tab finishes a word). Click a cable to inspect it. Tasks tick themselves off as you complete them; questions are answered in the box under each task. Your work is kept if you reload; Reset starts the network over.
Solution explanation
There were three faults. ipv6 unicast-routing was missing, so the router sent no Router Advertisements (no SLAAC, no gateway on the PCs) and wouldn't route IPv6. Gi0/1 had a typo in its prefix (:21:: instead of :20::), so it wasn't on the same /64 as PC2; you remove the wrong address with no ipv6 address ..., because an interface can hold several and adding the right one doesn't replace it. Finally, Gi0/1 was shut down.
Show solution
[PC1]
ipconfig
[R1]
enable
show ipv6 interface brief
configure terminal
ipv6 unicast-routing
interface g0/1
no ipv6 address 2001:db8:acad:21::1/64
ipv6 address 2001:db8:acad:20::1/64
no shutdown
end
show ipv6 route
[PC1]
ipconfig
ping 2001:db8:acad:20::10