A use case for a longer prefix with the same nexthop: F / \ D E | | B C \ / A
Suppose A is a customer of B and C. B has a large address space: 10.1.0.0/16. B allocates a subset to A: 10.1.1.0/24. B advertises the longer prefix to its backup provider C. C propagates it to E and then to F. B MUST advertise both 10.1.0.0/16 and 10.1.1.0/24 to D. D MUST propagate both of them to F. Otherwise, if F only receives 10.1.0.0/16 from D, then F will have the longer match 10.1.1.0/24 to E, but E is only the backup route. Thanks, Jakob. > -----Original Message----- > Date: Fri, 29 Apr 2016 08:17:41 -0400 > From: Alain Hebert <aheb...@pubnix.net> > To: "'NANOG list'" <nanog@nanog.org> > Subject: Friday's Random Comment - About: Arista and FIB/RIB's > Message-ID: <00ea292f-e779-25ad-ce89-eae897e95...@pubnix.net> > Content-Type: text/plain; charset=utf-8 > > While following that Arista chat... That reminded me of that little > afternoon project years ago. > > So I decided to find new hamsters, fire up that VM, refresh the DB's and > from the view point of a tiny 7206VXR/G1 with 2 T3 peers... > > The amount of superfluous subnet advertisement drop to ~120k from > ~166k from the previous snapshot. > > And this is the distribution by country. > > country | superfluous > --------------------+------------- > United States | 28254 > Brazil | 10012 > China | 7537 > India | 6449 > Russian Federation | 4524 > Korea, Republic of | 4062 > Saudi Arabia | 3297 > Australia | 2989 > Indonesia | 2878 > Hong Kong | 2251 > Thailand | 2093 > Canada | 2019 > Taiwan | 1955 > Ukraine | 1877 > Singapore | 1856 > Bulgaria | 1488 > Argentina | 1436 > Japan | 1403 > Mexico | 1351 > Chile | 1271 > > (Damn Canada, can't break top 10 again). > > PS: "Superfluous" is a nice way to say that the best path of a > subnet is the same as his supernet. And yes I'm aware of the Weekly > Routing Report, I was just curious to see it by country =D. > > ----- > Alain Hebert aheb...@pubnix.net > PubNIX Inc. > 50 boul. St-Charles > P.O. Box 26770 Beaconsfield, Quebec H9W 6G7 > Tel: 514-990-5911 http://www.pubnix.net Fax: 514-990-9443
