2 new GRH Tools: Which prefixes does my ASN miss? & Who misses my prefix?

Jeroen Massar jeroen at unfix.org
Thu Jan 18 20:47:33 CET 2007

Dear beloved Network Operators,

I've just finished adding a nice tool for you to figure out which IPv6
prefixes you are missing. It thus effectively shows you if you have
misconfigured filters somewhere between you and the destination.
This should keep you busy on your upcoming friday ;)

First a special tool for ASN's having a working peering with GRH:
"Which prefixes does my ASN miss?"

Just go to the normal DFP page, and choose your ASN and which RIR you
would like to take a look at, or all of them.
See http://www.sixxs.net/tools/grh/dfp/ under the heading of "Missing
DFP's per GRH participant" for this tool.

I have to admit that there is a small bug in here though, that is if one
or only a few ASN's do provide the route to GRH, GRH flags it as
'reachable', while actually it is not. This tool exposes that. I might
later on change the behavior of GRH in itself so that it actually needs
say, 50% of the GRH peers to carry the prefix before flagging the prefix
as 'seen'. This is why for prefixes one is missing, you should check how
many other ISP's see the prefix. That is why the "LG" link is present in
every row.

The second question "Who misses my prefix" can be answered by doing a
Looking Glass query, eg using the normal query:


One can also select to list all the non-GRH asns' which don't see the
prefix. These ASN's are picked up from all the ASN paths in the total
BGP tree and assuming that if they have one path, they should have the
rest too.

At the bottom, after the usual report, a report will form showing which
ASN's are seen in the AS paths for that prefix. It lists additionally if
those ASN's are peers of GRH. In the second part it will show a list of
GRH peers that don't carry the prefix.

Note that the 2610:78::/32 is seen/not seen 50/50. Thus clearly some
people need to start updating their filters and kicking their upstreams.

Enjoy your Fridays fixing them up :) *whistle*


PS: if you know a befriended (or enemy ;) ASN who is not peering yet
with GRH, don't hesitate to point them to the signup URL and get them to
participate, the more peers the better the quality of the data and the
easier problems can be determined and fixed, the signup URL is at:

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