> Since more than half the global routing table consists of /24 announcements, those are the first candidates for being filtered. More aggressive filters may even filter out everything smaller than the smallest assigned PA blocks, possibly with some exceptions for “the swamp,” the part of the Class C space assigned in pre-CIDR days(192.x.x.x and part of 193.x.x.x). The currently allocated smallest PA blocks are /20, but much of the Class C space is allocated to ISPs in /19 and larger blocks.
> Since more than half the global routing table consists of /24 announcements, those are the first candidates for being filtered. More aggressive filters may even filter out everything smaller than the smallest assigned PA blocks, possibly with some exceptions for “the swamp,” the part of the Class C space assigned in pre-CIDR days(192.x.x.x and part of 193.x.x.x). The currently allocated smallest PA blocks are /20, but much of the Class C space is allocated to ISPs in /19 and larger blocks.