Hello everyone and happy new year
This question is in some way related to https://supportforums.cisco.com/message/3806616
Imagine AS65200 anouncing block 10.10.0.0/22 to the internet.
Now for some reason we need to announce block 10.10.2.0/24 from AS65333.
How should routes from AS65200 be announced now?
As you stated, the /24 is more specific and traffic going to that subnet will use AS 65333
Other subnets from the /22 will use AS 65200
If you are peering with the same upstream, you can advertise the whole /22 via AS65200 and only advertise a /24 via AS65333. The /24 is more prefered at all times until your link goes down.
If you peer with more then one upstream, that you will need to make some fun changes...
We are from completely different upstream (different continents even) what are these fun changes?