169.254.0.0/16

joel jaeggli joelja at bogus.com
Sat Oct 20 19:22:38 UTC 2012


On 10/17/12 10:59 AM, Darren O'Connor wrote:
> I've just set up a vpn tunnel to Amazon's AWS and as part of the config they required me to configure to /30 tunnels using addressing from the 169.254.0.0/16 space.
>
> RFC3927 basically says that this address should only be used as a temp measure until the interface has a proper private or public address.
>
> So what's the consensus then? Is their a problem using this space as link-local address for routers here and there (I mean we have 65K addresses wasted in this block) or is it a strict no-no? And if no, why is Amazon using it?
Given the frequency with which adhoc networks are numbered out of this 
prefix, it's existence is far from wasted. The term waste is exercised 
far to liberally in the context of address mangement as far as I'm 
concerned.

If you are unconcerned with possible collisions with ephemeral uses of 
this space then I imagine you could reuse it for some internal purpose. 
It is probably important to be aware that unmanaged end systems will use 
it in an uncoordinated fashion (and make assumptions about the scope of 
addresses in that range) and that it would therefore be a good idea to 
limit applications to those which cannot be impacted by that behavior.

Amazon does number our VPC peer links out of there. coordinating the 
existance of multiple private clouds all numbered out of potentially 
overlapping rfc-1918 address space is probably the motivation for doing so.
> Thanks
>
> Darren
>   		 	   		
>




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