In this presentation I briefly describe the first version of IPv6 private or local network addressing - site-locals - and the issues that caused the IETF to replace them back in the early 2000s. I then describe their replacement, Unique Local Unicast Addresses. Finally, I provide an overview of how they are intended to be used in parallel with public IPv6 Internet addresses, without needing to use NAT. This is a shortened version of the same topic I presented on at AusNOG 2019.

1. NZNOG 2020
Getting
IPv6 Private Addressing
Right
Mark Smith
markzzzsmith@gmail.com
@ipv6tao
@markzzzsmith

2. IPv6 Private Addressing:
First Attempt

3. IPv6 Site-Local Addresses
IANA Allocation: fec0::/10

4. IETF IPv6 WG Circa 2002
What is a “site”?
Merge sites with no NAT or
renumbering?

5. “Site”?
site
”1. The place where anything is fixed;
situation; local position”
”2. A place fitted or chosen for any certain
permanent use or occupation”
https://en.wiktionary.org/wiki/site

6. “Site”
Really too fixed and
geographical.

7. Site-Local
Networking Issues

8. fec0::/10
fec0::/10
fec0::/10
IPsec
IPsec
IPsec

9. Distinguish instances?
Node internal
Site
Identifier?
VRFs in
billions of
IPv6 nodes?
Implementation COMPLEXITY!

10. Merging Site-Local Sites

11. Overlapping or Duplicated
Address Spaces
fec0::/10 fec0::/10
fec0::/10 fec0::/10

12. Lucky? Unique Subnets?
fec0:0:0:1::/64
fec0:0:0:2::/64
fec0:0:0:3::/64
fec0:0:0:a::/64
fec0:0:0:b::/64
fec0:0:0:c::/64
fec0:0:0:a::/64
fec0:0:0:b::/64
fec0:0:0:c::/64
fec0:0:0:1::/64
fec0:0:0:2::/64
fec0:0:0:3::/64

13. Unlucky. Duplicate Subnets.

14. NAT? NO.

15. Renumber Site Subnets?

16. Fundamental problem:
Non-Unique Destination
fec0:0:0:1::1/64 fec0:0:0:7::3/64 fec0:0:0:7::3/64
Want
Get

17. Uniquifying Addresses
Process - Renumbering
Function - NAT
Adding Context - Site ID
VRF

18. “Prevention is better than cure”
Desiderius Erasmus

19. UNIQUE’em
in the
FIRST PLACE.
ALL CONTEXTS!

20. http://www.bitsavers.org/pdf/xerox/ethernet/Ethernet_Rev2.0_Nov1982.pdf

21. IPv6 Private Addressing:
Unique Local Unicast
Addressing

25. IANA Prefix
Unique Local Unicast Addresses
fc00::/7

26. Locally Assigned (L) Bit
Type Purpose L Bit Prefix Status
ULA-C
Central ULA
Prefix
Registry
L=0 fc00::/8 Never took off
ULA-L
Local
Network
Generated
L=1 fd00::/8 All current ULAs
All currently valid ULAs start with fd.

27. 40 bit Global ID

28. 40 bit Global ID

29. 40 bit Global ID
“Their values SHOULD NOT be
generated by a human.” -
Me!
Humans may not [RANDOM].

30. This presentation?

31. 40 bit Global ID
AusNOG 2011

32. 40 bit Global ID
AusNOG 2011

33. Site-Locals and their
problems reproduced!

34. ULA-L Global ID Algorithm
1. Get current time of day
2. Get a likely unique system identifier e.g. serial number
3. Combine and hash with SHA-1
4. Use lower 40 bits of hash as Global ID
5. Append to 0xfd to produce ULA /48 (0xfd = ULA-L)
Brief summary:

35. Example
My home ULA:
fd██:████:████:████::/48

36. ULA Generators
RFC 7084,
“Basic Requirements for
IPv6 Customer Edge
Routers”
Android Apps
Online - search “IPv6
ULA generator” iPhone Apps(?)

38. Routing
fc00::/7 and longer prefixes
- by default, don’t send or accept in BGP
fd██:████:████:████::/48
- network operator override to allow inter-
ULA domain routing

39. Other Operational Things

40. Would GUAs do?
Also known as public IPv6 Internet addresses

41. Not really
GUA ULA
Globally Unique
(Assured or
Likely)
✓ ✓
Designed for
Internet
connectivity/reach
ability
✓ ✗
Assigned by RIR/LIR/ISP Local
administrator
or local CPE
$$$ Per
Month/Annum
$0 forever

43. Why Both?
Internal communication
independent of
external addressing

44. IPv6 Multi-Addressing

45. IPv4 Private OR Internet
Addressing
Serial Addressing
Private Addressing Internet Addressing
NAT

46. IPv6 Private AND Internet
Addressing
Internet (GUA) Addressing
Private (ULA) Addressing
Parallel Addressing

47. IPv6 Node
Interface Multi-Addressing
Link Local
ULAs
Link Locals
GUAs

48. IANA Allocation: fe80::/10

49. Address Space IANA Prefix Communication
Scope
Link Local fe80::/10 Local Link
Unique Local
Unicast Addresses
fc00::/7 Local Network
Global Unicast
Addresses
2000::/3 Global Internet

50. NO NAT ✓

51. UNIQUE your ULAs!

52. Questions?
CC image courtesy of Kiwithing
http://www.flickr.com/photos/kiwisaotome/
8261132558/sizes/c/
in/photostream/