Big prefix block separation to different public AS's. How to anounce?

[netone.cisco]

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?

• Can I maintain the whole /22 block since 10.10.2.0/24 from AS65333 is more specific?
• Or should I now break AS65200 announcement into smaller prefixes completelly excluding .2.0/24 ?( .0.0/23 and .3.0/24)

Thanks all

Mario

                 

10.10.10.0/22      (AS65200)

10.10.10.0/23   (AS65200)

10.10.2.0/24 (AS65333)

10.10.3.0/24 (AS65200)

[Edison Ortiz]

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

Regards,

[Ahad Aboss]

Mario,

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...

[netone.cisco]

Ahad,

We are from completely different upstream (different continents even) what are these fun changes?

Mario