What's special about 151& Blocks

Unanswered Question
Feb 23rd, 2010

I saw a config recently with the above ranges.  I assumed it was valid external IP's, but it seems these blocks are not routable on the Internet.

What is so special about these blocks?


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msv Tue, 02/23/2010 - 11:52

If you lookup these blocks on ARIN, etc. they are not assigned to anyone.  Ran traceroute from a few of my internet routers, and it didn't go anywhere, and no bgp routes for it

Paolo Bevilacqua Tue, 02/23/2010 - 12:01

ARIN dbase can have gaps. As you see, these are European numbers. For some reason 151.x.x.x is also familiar to me.

Giuseppe Larosa Tue, 02/23/2010 - 12:21

Hello Paolo,

>> For some reason 151.x.x.x is also familiar to me.

Telecom Italia AS3269 uses some of 151.x.x.x


yes, and are not present in public internet table, this means they are not assigned but does not imply they are not public routable addresses.

Hope to help


vmiller Tue, 02/23/2010 - 11:54

my quick look showed no 151.0 or 152.0 netblock. they

are class b, starting at 15x.1

152.1.x.x is NC state Univeristy

151.1.x thru 151.100 is:

OrgName:    RIPE Network Coordination Centre
OrgID:      RIPE
Address:    P.O. Box 10096
City:       Amsterdam
PostalCode: 1001EB
Country:    NL

NetName:    RIPE-ERX-151-1-0-0
NetHandle:  NET-151-1-0-0-1
Parent:     NET-151-0-0-0-0
NetType:    Early Registrations, Transferred to RIPE NCC
Comment:    These addresses have been further assigned to users in
Comment:    the RIPE NCC region.  Contact information can be found in
Comment:    the RIPE database at http://www.ripe.net/whois
RegDate:    2003-04-02
Updated:    2003-06-18

Paolo Bevilacqua Tue, 02/23/2010 - 11:46

What search results can you bring to support your point ?

inetnum: -
netname:         EU-ZZ-151
descr:           Various Registries
country:         EU # Country is really world wide
remarks:         These addresses were issued by
              The IANA before the formation of
              Regional Internet Registries.
org:             ORG-NCC1-RIPE
admin-c:         IANA1-RIPE
tech-c:          IANA1-RIPE
mnt-by:          RIPE-NCC-HM-MNT
mnt-lower:       RIPE-NCC-HM-MNT
mnt-routes:      RIPE-NCC-RPSL-MNT
source:          RIPE # Filtered
msv Tue, 02/23/2010 - 12:11

to be exact, they were using &

Brandon Svec Tue, 02/23/2010 - 16:05

Interesting thread.  Just to add-  I recently came across a customer using internally and I was sure it was not correct.  They argued otherwise and I found this interesting link while researching:


I still think it is incorrect and you should always use rfc1918 for internal, but they may have had some point at least..


Paolo Bevilacqua Wed, 02/24/2010 - 01:03

Hi Brandon how are ya m8 ?

What happens, sometime people is not happy with the standard private space, mainly because everyone else is using it. They are afraid that it will overlap with other part of the network, a company acquisiton, or it just looks more serious. I also have seen ISPs that literally ran out of private space. So at that point they begin guessing which public space has the less chances to be ever used on the Internet. From there some wild picks, 23/8, 128, 151 and whatelse.

Riight or wrong, that is what is being done everyday.


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