On 05/04/18 19:20, Ryan Harris via mailop wrote:
> If we advertised (announced) IP space with a /20 CIDR via BGP for
> months, then stopped that advertisement for 7 days and re-advertised
> but with 2 different /21 CIDR ranges, would this produce a negative
> effect to our IPs reputation? 
> I would think that due to the previous /20 range being advertised
> (announced) on BGP this would be a moot issue, but wanted to reach out
> and inquire if the change in CIDR or the blackout 7 day period of no
> announcement would cause any issues with our reputation or acceptance
> of email from those IP ranges.

I've no idea about the reputation ideas, but I'm just thinking in terms
of network.

Are you getting another AS number?

Do you have any connectivity between the 2 places where you are
announcing the /21?     You could announce the /20 from both sides as
well as the /21.

In theory, the most specific (/21) will win.    You might get some
traffic into the `wrong` site, but if you have a link between, you can
deliver it back.

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