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Internet => General Internet => Topic started by: burakkucat on March 16, 2020, 12:10:39 AM

Title: IETF RFC 5735 -- Special Use IPv4 Addresses
Post by: burakkucat on March 16, 2020, 12:10:39 AM
For convenience, the Summary Table, Section 4 of IETF RFC 5735 (https://tools.ietf.org/pdf/rfc5735), is reproduced below.


RFC 5735               Special Use IPv4 Addresses           January 2010


4.  Summary Table

Address Block       Present Use                Reference
------------------------------------------------------------------
0.0.0.0/8           "This" Network             RFC 1122, Section 3.2.1.3
10.0.0.0/8          Private-Use Networks       RFC 1918
127.0.0.0/8         Loopback                   RFC 1122, Section 3.2.1.3
169.254.0.0/16      Link Local                 RFC 3927
172.16.0.0/12       Private-Use Networks       RFC 1918
192.0.0.0/24        IETF Protocol Assignments  RFC 5736
192.0.2.0/24        TEST-NET-1                 RFC 5737
192.88.99.0/24      6to4 Relay Anycast         RFC 3068
192.168.0.0/16      Private-Use Networks       RFC 1918
198.18.0.0/15       Network Interconnect
                    Device Benchmark Testing   RFC 2544
198.51.100.0/24     TEST-NET-2                 RFC 5737
203.0.113.0/24      TEST-NET-3                 RFC 5737
224.0.0.0/4         Multicast                  RFC 3171
240.0.0.0/4         Reserved for Future Use    RFC 1112, Section 4
255.255.255.255/32  Limited Broadcast          RFC 919, Section 7
                                               RFC 922, Section 7
Title: Re: IETF RFC 5735 -- Special Use IPv4 Addresses
Post by: CarlT on March 16, 2020, 01:39:28 PM
A few of those are changing pretty soon. A whole /8 for loopbacks? The /4 for 'Future Use'? The /4 for multicast? Multicast has become largely a non-issue weirdly so I expect that to be cut back.

Worth keeping an eye on things as there's no way those insanely large allocations for various things are remaining intact given the need for IPv4 address space.
Title: Re: IETF RFC 5735 -- Special Use IPv4 Addresses
Post by: burakkucat on March 16, 2020, 03:49:58 PM
Agreed. Ten years on, those allocations "probably" need revision.
Title: Re: IETF RFC 5735 -- Special Use IPv4 Addresses
Post by: Weaver on March 16, 2020, 11:42:07 PM
How much work would it be to allow the use of the /8’s (bar one single IP) at 127.0.0.0 and even 0.0.0.0? Doesn’t everyone only use 127.0.0.1 and 0.0.0.0 respectively, and no other addresses?
Title: Re: IETF RFC 5735 -- Special Use IPv4 Addresses
Post by: burakkucat on March 17, 2020, 12:07:05 AM
Doesn’t everyone only use 127.0.0.1 and 0.0.0.0 respectively, and no other addresses?

Probably, yes. But then there will always be a corner-case.
Title: Re: IETF RFC 5735 -- Special Use IPv4 Addresses
Post by: Weaver on March 17, 2020, 01:07:11 AM
Multicast just doesn’t seem to be happening at all. Even AA, one of the very geekiest of ISPs, does not support it although they have talked about it, but no one is asking for it anyway. There’s a vast amount of space to be reclaimed at 240.0.0.0/4 - how much could be reclaimed and how much work would it be? Does it involve fixes to operating systems at all?

I have firewalled off almost all of the addresses in the RFC5735 summary table such that tx to those addresses is blocked as well as rx, although rx is not an issue because of the usual stateful firewall ‘Dracula and the maiden at the window’ default firewalling rule. Ditto for IPv6 too.

A couple of questions: how many ISPs block upstream traffic destined for the evil RFC5735 dest addresses? Also do ISPs block bogus traffic with a source address in the evil RFC5735 address ranges, be it upstream or downstream?

You could perhaps test it for upstream, but downstream might be more awkward unless you have your own server hosted somewhere in the internet, and even then responsible anti-spoofing and anti-bogon filtering might ruin the experiment.
Title: Re: IETF RFC 5735 -- Special Use IPv4 Addresses
Post by: aesmith on March 22, 2020, 04:20:37 PM
Multicasts are used locally, for example for routing protocols.  Those I'm aware of all use the bottom end of 224 and 225, but of course that's not an exhaustive list.
Title: Re: IETF RFC 5735 -- Special Use IPv4 Addresses
Post by: CarlT on March 22, 2020, 08:42:10 PM
How much work would it be to allow the use of the /8’s (bar one single IP) at 127.0.0.0 and even 0.0.0.0? Doesn’t everyone only use 127.0.0.1 and 0.0.0.0 respectively, and no other addresses?

Some OS have been modified to allow use of them already. Modification of BOGONS filters which has been done in the past.
Title: Re: IETF RFC 5735 -- Special Use IPv4 Addresses
Post by: Weaver on March 24, 2020, 05:43:04 AM
Sorry, I was only thinking about multicast across the Internet, and forgot about LAN-local usage.