Best Current Practice (BCP) RFCs provide operational guidance for running networks reliably.
BCP (RFC ): Ingress Filtering. Block packets with source addresses that should not come from your network. Prevents IP spoofing and reflection attacks.
BCP : ICMP Filtering. Defines which ICMP types to allow. Blocking all ICMP breaks path MTU discovery.
Why BCPs matter:
BCPs represent collective wisdom from operators worldwide. They document solutions to problems others solved. Ignoring them means learning the hard way through outages.