Anycast but for egress

Joe Maimon jmaimon at
Thu Jul 29 20:58:34 UTC 2021

Vimal wrote:
> (Unsure if this is the right forum to ask this question, but here goes:)
> From what I understand, IP Anycast can be used to steer traffic into a 
> server that's close to the client.
> I am curious if anyone here has/encountered a setup where they use 
> anycast IP on their gateways... to have a predictable egress IP for 
> their traffic, regardless of where they are located?
> For example, a search engine crawler could in principle have the same 
> IP advertised all over the world, but it looks like they don't...  I 
> wonder why?
> -- 
> Vimal
Its definitely possible, but would need a layer of software (kernel 
mode) on all the anycast holders synchronizing state to ensure 
asymmetric replies/connections get forwarded/shifted to the correct host.

If the goals are worth that kind of effort is another question. And 
performance is likely to be "tricky".

More information about the NANOG mailing list