" It has been common for network administrators to filter IP traffic
from and BGP prefixes of unallocated IPv4 address space. Now that
there are no longer any unallocated IPv4 /8s, this practise is more
complicated, fragile and expensive. Network administrators are
advised to remove filters based on the registration status of the
This document explains why any remaining packet and BGP prefix
filters for unallocated IPv4 /8s should now be removed on border
routers and documents those IPv4 unicast prefixes that should not be
routed across the public Internet."
Working Group Summary
"There were no standout notes in the WG process for this document."
"This document covers operational guidance, not code. As such there are no implementations and this is not a protocol."
RFC Editor Note
Network operators who only wish to filter traffic originating from
addresses that should never be routed across the Internet, Martians,
can deploy a set of packet and prefix filters designed to block
traffic from address blocks reserved for special purposes. These
- 0.0.0.0/8 (Local identification) [RFC1122];
- 10.0.0.0/8 (Private use) [RFC1918];
- 127.0.0.0/8 (Loopback) [RFC1122];
- 169.254.0.0/16 (Link local) [RFC3927];
- 172.16.0.0/12 (Private use) [RFC1918];
- 192.0.2.0/24 (TEST-NET-1) [RFC5737];
- 192.168.0.0/16 (Private use) [RFC1918];
- 198.18.0.0/15 (Benchmark testing) [RFC2544];
- 198.51.100.0/24 (TEST-NET-2) [RFC5737];
- 203.0.113.0/24 (TEST-NET-3) [RFC5737];
- 188.8.131.52/4 (Multicast) [RFC5771]; and
- 240.0.0.0/4 (Future use) [RFC1112].
A full set of special use IPv4 addresses can be found in [RFC5735].
It includes prefixes that are intended for Internet use.
Network operators may deploy filters that block traffic destined for Martian prefixes. Currently, the Martian prefix table is
defined by [RFC 5735] which reserves each Martian prefix for some specific, special-use. If the Martian prefix table
ever changes, that change will be documented in an RFC that either updates or obsoletes [RFC 5735].