- The document discusses the 23.128.0.0/10 IPv4 address block which was set aside by ARIN to facilitate IPv6 deployment. - It provides details on the minimum (/28) and maximum (/24) allocation sizes from this block. Only a few allocations have been made so far. - Route views data shows 15 routes being advertised from prefixes within this block, with most being /24s but some longer prefixes like /25s also seen. - Best current practices recommend network operators check their prefix filters allow these longer prefixes from 23.128.0.0/10 to avoid reachability issues as more allocations are made.

1. Japan Internet Exchange Co., Ltd.
Masataka MAWATARI <mawatari@jpix.ad.jp>
23.128.0.0/10
APRICOT 2016 @ Auckland, New Zealand
Lightning Talk

2. What’s 23.128.0.0/10 ?
2
• “Dedicated IPv4 block to facilitate IPv6 Deployment”
– e.g. dual stack DNS servers, and NAT-PT or NAT464
translators
(https://www.arin.net/policy/nrpm.html#four10)
ARIN has placed 23.128.0.0/10 in its reserves in
accordance with the policy "Dedicated IPv4 block
to facilitate IPv6 Deployment" (NRPM 4.10).
There have been no allocations made from this
block as of yet, however, once we do begin issuing
from this block, the minimum allocation size for
this /10 will be a /28 and the maximum
allocation size will be a /24.
https://www.arin.net/announcements/2014/20140130.html

3. Difference from the others?
/22 or /24 is fundamental minimum size of IPv4
address distribution and IPv4 address transfer in the
RIRs/NIRs.
– AFRINIC
• https://www.afrinic.net/en/library/policies/126-afpub-2005-v4-001
– APNIC
• https://www.apnic.net/publications/research-and-insights/min-prefix
– ARIN
• https://www.arin.net/knowledge/ip_blocks.html
– LACNIC
• http://www.lacnic.net/en/web/lacnic/ipv4-isp
– RIPE NCC
• https://www.ripe.net/participate/policies/proposals/2014-01
– The minimum allocation size has been removed as the policy for the final
/8 block
3

4. Advertised routes from 23.128.0.0/10 block
(from route-views.routeviews.org)
4
• アドレスブロックの大きさ
route-views>show ip route
--- skip ---
B 23.128.0.0/24 [20/0] via 216.218.252.164, 4w3d
B 23.128.24.0/24 [20/0] via 193.0.0.56, 4d12h
B 23.128.25.0/25 [20/0] via 193.0.0.56, 4d12h
B 23.128.25.240/28 [20/0] via 193.0.0.56, 4d12h
B 23.128.124.0/24 [20/0] via 193.0.0.56, 4d12h
B 23.128.125.0/25 [20/0] via 193.0.0.56, 4d12h
B 23.128.125.240/28 [20/0] via 193.0.0.56, 4d12h
B 23.136.0.0/24 [20/98] via 129.250.0.11, 3w5d
B 23.144.0.0/24 [20/19000] via 134.222.87.1, 1d16h
B 23.160.0.0/24 [20/0] via 103.247.3.45, 4w3d
B 23.168.0.0/24 [20/0] via 216.218.252.164, 3d17h
B 23.172.0.0/24 [20/7] via 129.250.0.11, 2w5d
B 23.176.0.0/24 [20/0] via 216.218.252.164, 4w3d
B 23.180.0.0/24 [20/0] via 216.218.252.164, 1w3d
B 23.188.0.0/24 [20/0] via 216.218.252.164, 5d08h
Total 15 routes

5. Advertised routes from 23.128.0.0/10 block
(from route-views.routeviews.org)
5
• アドレスブロックの大きさ
route-views>show ip route
--- skip ---
B 23.128.0.0/24 [20/0] via 216.218.252.164, 4w3d
B 23.128.24.0/24
B 23.128.25.0/25
B 23.128.25.240/28
B 23.128.124.0/24
B 23.128.125.0/25
B 23.128.125.240/28
B 23.136.0.0/24 [20/98] via 129.250.0.11, 3w5d
B 23.144.0.0/24 [20/19000] via 134.222.87.1, 1d16h
B 23.160.0.0/24 [20/0] via 103.247.3.45, 4w3d
B 23.168.0.0/24 [20/0] via 216.218.252.164, 3d17h
B 23.172.0.0/24 [20/7] via 129.250.0.11, 2w5d
B 23.176.0.0/24 [20/0] via 216.218.252.164, 4w3d
B 23.180.0.0/24 [20/0] via 216.218.252.164, 1w3d
B 23.188.0.0/24 [20/0] via 216.218.252.164, 5d08h
Total 15 routes
RIPE NCC RIS
- ARIN prefix reachability study
（Origin AS = 12654）6 routes
https://labs.ripe.net/Members/emileaben/has-the-
routability-of-longer-than-24-prefixes-changed

6. Prefix filter as a BCP
(Best Current Practice)
6
https://nsrc.org/workshops/2014/pacnog15-bgp/raw-attachment/wiki/Track1Agenda/05-BGP-BCP.pdf
http://www.janog.gr.jp/doc/janog-comment/jc1001.txt

7. 7
https://nsrc.org/workshops/2014/pacnog15-bgp/raw-attachment/wiki/Track1Agenda/05-BGP-BCP.pdf
http://www.janog.gr.jp/doc/janog-comment/jc1001.txt
Will we add
“permit 23.128.0.0/10 ge 24 le 28“
on the configuration in our routers?
Prefix filter as a BCP
(Best Current Practice)

8. Conclusion
8
• Address distribution from 23.128.0.0/10 pool has already
started.
• As of Feb. 2016, longer-than-/24 block hasn’t been distributed
except the RIPE NCC experimental assignments. So any
reachability issues don’t seem to be happening with the route
filter (deny longer-than-/24 routes) of the xSP routers.
• It’s not sure when longer-than-/24 assignment will happen for
non-experiment. Checking route filter configuration on your
routers is recommended now.
• Address policy in RIRs/NIRs sometimes makes an impact on the
network operation. So stay tuned for the address policy.
• Any comments?

9. 9