Re: Using RFC1918 on Global table as Loopbacks

[Niels Bakker <niels=nanog () bakker net>]

* GutierrezJ () westmancom com (Javier Gutierrez) [Thu 05 Oct 2023, 19:25 CEST]:
> I have recently encountered some operational differences at my new 
> organization that are not what I have been exposed to before, where 
> the loopback of the core network devices is being set from RFC1918 
> while on the global routing table. I'm sure this is not a major 
> issue but I have mostly seen that ISPs use global IPs for loopbacks 
> on devices that would and hold global routing.
>
> My question is, what is the most used or recommended way to do this, 
> if I continue to use RFC1918 I will save some very much desired 
> public address space, but would this come back to bite me in the 
> future?

The recommendation is to make Router-IDs globally unique. They're used 
in collision detection. What if you and a peer pick the same non 
globally unique address? Any session will never come up.

You need globally unique IP addresses on routers anyway, to send ICMP 
error packets from.


        -- Niels.