On Wed, Dec 19, 2018 at 12:12 PM Thomas Bellman <bell...@nsc.liu.se> wrote: > On 2018-12-19 20:47 MET, valdis.kletni...@vt.edu wrote: > > There was indeed a fairly long stretch of time (until the CIDR RFC came out > > and > > specifically said it wasn't at all canon) where we didn't have an RFC that > > specifically said that netmask bits had to be contiguous. > > How did routers select the best (most specific) route for an address? > If the routing table held both (e.g.) 10.20.30.0/255.255.255.64 and > 10.20.30.0/255.255.255.32, then 10.20.30.97 would match both, and have > the same number of matching bits.
Easy: .97 matches neither one because 64 & 97 !=0 and 32 & 97 != 0. That's a 0 that has to match at the end of the 10.20.30. The problem is 10.20.30.1 matches both, so which one takes precedence? Can't have a most-specific match when two matching routes have the same specificity. I'm guessing the answer was: the routing protocols didn't accept netmasks in the first place and you were a fool to intentionally create overlapping static routes. Regards, Bill -- William Herrin ................ her...@dirtside.com b...@herrin.us Dirtside Systems ......... Web: <http://www.dirtside.com/>
