BGP prefix lists evaluate an exact match when not using
ge statements on the end. For example, when your prefix list includes only
ip prefix-list PREFIX-FROM-A seq 15 permit 192.168.0.0/24, your neighbour MUST be sending that prefix as an exact
/24 to be accepted.
le <cidr> to the end of a prefix list term, this tells our router to evaluate the prefix by matching up to
<cidr> as long as its within the prefix.
For example, using your statement from the original post:
ip prefix-list PREFIX-FROM-A seq 15 permit 192.168.0.0/24 le 32, this would allow anything within that
/24 with the CIDR of the prefix being anywhere from
/24 through to
/32. Here are some further examples that would be accepted when using
le 32 on the end of your prefix list term:
192.168.0.1/32 - ACCEPTED
192.168.0.0/24 - ACCEPTED
192.168.0.0/23 - REJECTED
192.168.0.128/25 - ACCEPTED