On Wed, Dec 19, 2018 at 12:12 PM Thomas Bellman <bellman@nsc.liu.se> wrote:
On 2018-12-19 20:47 MET, valdis.kletnieks@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 ................ herrin@dirtside.com bill@herrin.us Dirtside Systems ......... Web: <http://www.dirtside.com/>