Martian and RFC1918 addresses

Philip Smith pfs at
Sat Jul 31 07:12:27 UTC 1999

The list we documented in IOS Essentials was one presented a few (I don't
remember how many) IEPGs ago, and was implemented by several ISPs... Indeed
the next version of the document mentions only those listed in Bill's draft
- I'd suggest we all stay with that as it is probably the first attempt to
document non-routable nets...

I don't remember the history of the other network blocks listed anymore,
certainly not without a lot of e-mail archive trawling...


At 19:57 29/07/99 -0400, Daniel Senie wrote:
>rfuller at wrote:
>> I have been reading Cisco's "Essential IOS Features Every ISP Should
>> Consider" document and came across a section called Martian and RFC1918
>> networks.  It is discussing different bogus or reserved networks that
>> should be filtered by every ISP.  In the list are some addresses I thought
>> were legal and after checking the ARIN Whois database, some of them seem to
>> be.  Can anyone give me some additional information as to the need to
>> filter the following networks:
>Some of these are indeed questionable. I recommend using Bill Manning's
>draft on this subject (draft-manning-dsua-01.txt) as a guide, rather
>than Cisco's document. Page 27 of Cisco's document has a sample
>access-list which does match Bill's document. Page 59 of the document
>has the list you saw and were concerned about. It claims the information
>comes from the NANOG list. Hmmm...
>>             reserved for IANA
>>          this belongs to Ford
>>            reserved for IANA
>>         this belongs to SUN
>>         IANA use for local link numbers???
>169.254/16 should never be routed. It's used for self assigned
>addresses, and is useful in small networks especially. Win98 takes
>advantage of this if DHCP fails to find a server. It allows a small
>cluster of systems to select unique IP addresses, and in the case of
>Windows, they'll then talk Netbios over IP on that. It eliminates the
>need to use Netbeui, which in itself is a good thing.
>>      reserved for IANA
>192.0.2/24 is set aside for use in documentation and examples. By
>ensuring this block is not routed, folks who type the exact values from
>their documentation don't screw up someone else's network.
>>      no ARIN match
>>         no ARIN match
>>          this belongs to SUN
>> If you can elaborate on what they are used for and if any problems would
>> arise from filtering these networks, it would be appreciated.  If you could
>> also please include where you found the information, I would appreciate it.
>> Some of them belong to companies, so why would you filter them?  Are they
>> development networks for Ford and SUN?  Are there any other martian
>> networks that should be filtered?
>Lots of folks used to set up their Sun workstations on private networks
>using Sun's IP space, 'cause that's what was in the Sun documentation.
>The only thing I can figure is the other blocks in the example must be
>ones that were frequently used in documentation and got used in a lot of
>private networks that later connected to the public network. Anyone have
>better insight into these?
>Daniel Senie                                        dts at
>Amaranth Networks Inc.  

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