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From AS4
Welcome to AS4, a Wiki for all sorts of information related to 32-bit ASNs.
What You Can Find Here
Background
We are running out of 16-bit ASNs, and the first RIR could run out by sometime in 2011 at the current allocat ion rate. So, we need to increase the number of ASNs to accommodate the growth of the Internet. There are 65,536 16-bit ASNs, and increasing the size to 32 bits gives us 4,294,967,296 ASNs. Take a look at the Useful Links page for more information on the design, implementation and overview of how 32-bit ASNs work.
RIR Allocation Schedule
| 2007 and 2008 | January 1, 2009 | January 1, 2010 |
|---|---|---|
| 16-bit only ASNs are allocated by default 32-bit only ASNs can be requested | 32-bit only ASNs are allocated by default 16-bit only ASNs can be requested | 32-bit ASNs are allocated, there is no distinction between 16-bit only and 32-bit only ASNs |
What is Affected by This Transition?
Allocation and deployment of 32-bit ASNs will affect everyone, even if you have a 16-bit ASN, because everything in your network still thinks that ASNs are 16-bits long. The following things should be investigated for how they will be affected by the transition:
- Routers/routing software
- Routing policies
- Peering policies
- Engineering and NOC staff knowledge
- Network management tools
- Network monitoring tools
- Customer management tools
- Sales staff knowledge
You Need to Upgrade Now
Everything in your network needs to be upgraded to understand 32-bit ASNs. Since AS 23456 is used to represent all 32-bit ASNs on routers that use 16-bit ASNs, it is impossible to know the real ASN. The implications are:
- You could peer with AS 23456, which represents different ASNs, multiple times
- You will see prefixes with 23456 everywhere in the AS path
- Routing policies using AS path or communities cannot match on 32-bit ASNs
- MEDs could cause the best path to change if peering with multiple AS 23456 peers
- Flow data will have lots of 23456 ASNs
What You Should Do
- Evaluate the impact on your network, tools, and staff right away
- Ask your vendors for 32-bit ASN support and tell them if you prefer asplain notation
- Develop an upgrade plan, test new code
- Upgrade
Terminology
- 2-octet, 2-byte, 16-bit, ASN16, and OLD all mean: AS 0 – 65,535
- 4-octet, 4-byte, 32-bit, ASN32, NEW, and AS4 all mean: AS 0 – 4,294,967,295
- The ARIN terminology is nicely unambiguous:
"16-bit only AS numbers" refers to AS numbers in the range 0 – 65,535
"32-bit only AS numbers" refers to AS numbers in the range 65,536 – 4,294,967,295
"32-bit AS numbers" refers to AS numbers in the range 0 – 4,294,967,295
On this Wiki we will use the 16-bit and 32-bit terminology when distinction is needed.
