Practical IPv6 Troubleshooting while Setting up the Troopers Network

Hello Everyone,

Troopers is right around the corner and as I am responsible for the whole conference network I wanted to make sure that everything is working as expected. I went to the venue on Friday because of two things I wanted/needed to setup. Compared to last year’s setup we had a couple of changes in regards to the provider connection (resulting in some changes for our network setup). First, we now have a rather big pipe for the uplink and more importantly (well that depends on the point of view ;)) there is a native IPv6 connection. Before that I had to tunnel all IPv6 traffic from the venue to one of our gateways and to forward it out (as native IPv6) from there. As this step isn’t necessary anymore, and the staff on the venue isn’t that experienced with IPv6, I had in mind to setup and verify that IPv6 is working as desired. The router used over there is a Mikrotek Routerboard. As I haven’t worked with these devices before, I was curious whether everything works as it should ;).

After configuring the IPv6 address on the WAN interface I tried to install a default route pointing to the uplink’s Global Unicast Address. But to my surprise, the Mikrotek router kept stating that the next hop was unreachable. This was odd, as the provider’s device was happily answering to pings from the Mikrotek’s command line. Additionally, the Mikrotek router does not install a route when it can’t reach the next hop configured (which is actually not that bad as it at least prevents fat fingering the address). It still didn’t make any sense. After googling around (I found the Mikrotek documentation a little bit lackluster) and trying some other things it still didn’t work. As a last resort, I told myself “screw it and let’s try with the link local address of the provider router”, but how do I get this address as I only was provided with the GUA? Right, looking at the Neighbor Cache of the Mikrotek router I was able to quickly find the link local address of the next hop.

After using this address (together with the interface) as the next hop it started working, by magic. At least I can now sleep better as it is one less thing I have to worry about ;).
Moral of the story: Still in 2015 don’t expect a device to behave like it should when it comes to IPv6. Unfortunately, I wasn’t able to follow this strange behavior up due to time constraints, but it is working and you can enjoy for the first time native IPv6 in the conference network.

If you want to know more about the general conference setup please stop by for my talk at the IPv6 Security Summit.

See you all in a week!



Leave a Reply

Your email address will not be published. Required fields are marked *