SixXS::Sunset 2017-06-06
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What is a Ghost Route?


As IPv6 Routing Stability has improved over the years we have concluded the GRH project.

The GRH pages remain for a historical perspective.

The ULA Registry remains active.

Or "GRH Explained"

First we will take Ghosts Routes of 2003-03-18 12:33 by the hand which shows 3 very long AS Paths:

2001:788::/32 - 6 ghosted paths
3ffe:1f00::/24 - 24 ghosted paths
3ffe:8060::/28 - 41 ghosted paths

The first one is quite probably just BGP latency and it will disappear in a few moments (could take up a couple of hours though) I know this quite for sure as a number of ASn's in the path don't have it anymore, the green ones participate in the project. Thus it will disappear quite fast. The system of this 'ghost' mostly has to do with overloaded small routers doing to many things. eg using a small cisco 2600 as a backbone router and thinking it is sufficient but in the mean time they do take quite some time to propagate any changes in the BGP tree.

The 3ffe:1f00::/24 has been lingering for almost a month now compared to the above date and I expect it to stay there for some time too. The last one is 'new' but I expect it to go away again as it is still being announced and is currently being seen correctly at some places.

What do I call a Ghost Route you ask, well, let's look at the ASpath of 3ffe:1f00::/24, you will notice that it is quite long. Averaging currently at 30 ASN's while normal ASpaths have 12 ASn's max and an average of 5. The length isn't the real problem, the problem is the fact that the path doesn't exist at all and that it gets generated by one of the intermediate ASn's. We suspect 10318 (the orange one) for doing this but can't quite prove it. Also the people maintaining it are not reachable unfortunatly.

When you traceroute6 any IP in 3ffe:1f00::/24 you will notice that you will end up nowhere. Thus the complete /24 is blackholed by a route that doesn't really exist but is there anyways: ghost.

Thus we are trying to get as close to the problem as possible and like to have a view into as much systems as possible. This also has some other nice advantages like the DFP visibility statistics and the Distributed Looking Glass.

You might also notice that 3ffe:8060::/28 is seen as coming over AS10318 by, but the rest of the world thinks that it's who is giving the path to AS10318.

If we now check Ghosts Routes of 2003-03-18 14:04 one will notice that 2001:788::/32, as predicted, is normal again and so is 3ffe:8060::/28. The ghost for 3ffe:1f00::/24 still remains though.

At 2003-03-26 20:22 the 3ffe:1f00::/24 ghost suddenly disappeared. I would like to thank the invisible powers that be for doing the cleanup.

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