Chapter 2 Advanced Routing for FortiOS 5.0 : Routing Information Protocol (RIP) : Troubleshooting RIP : Debugging IPv6 on RIPng
  
Debugging IPv6 on RIPng
The debug commands are very useful to see what is happening on the network at the packet level. There are a few changes to debugging the packet flow when debugging IPv6.
The following CLI commands specify both IPv6 and RIP, so only RIPng packets will be reported. The output from these commands will show you the RIPng traffic on your FortiGate unit including RECV, SEND, and UPDATE actions.
The addresses are in IPv6 format.
diagnose debug enable
diagnose ipv6 router rip level info
diagnose ipv6 router rip all enable
These three commands will:
turn on debugging in general
set the debug level to information, a verbose reporting level
turn on all rip router settings
Part of the information displayed from the debugging is the metric (hop count). If the metric is 16, then that destination is unreachable since the maximum hop count is 15.
In general, you should see an update announcement, followed by the routing table being sent out, and a received reply in response.
For more information, see “Testing the IPv6 RIPng information”