Hi Everyone
how to deny all routes have the first 3-octets 10.100.20 and subnet mask range 24->29 ?
i`ve two solutions to do that
solution#1
10.100.20.0/24
10.100.20.0/24 ge 25 le 29
solution#2
10.100.20.0/24 le 29
but what is the difference between both solutions (solution#1 and solution#2)
10.100.20.0/24
10.100.20.0/24 ge 25 le 29
vs
10.100.20.0/24 le 29
???
Hello major133,
Both solutions you wrote will work, but the second solution is the more elegant one.
In reality, if a router sends you a routing update about a prefix, and indicates that the first 24-bits of that prefix are:
00001010 01100100 00010100 (10.100.20)
…then that update will NEVER contain an associated mask anything less than a /24 (otherwise there would be no need to specify all 24-bits in the prefix). So that’s why your second solution is the best one.