Acee Lindem <[email protected]> writes:
On Sep 18, 2025, at 11:05 AM, Peter Psenak <[email protected]> wrote:
Hi Acee,
On 18/09/2025 16:32, Acee Lindem wrote:
The AC-flag simply indicates that the prefix has been configured as anycast -
i.e. originated by multiple routers.
[...] where and how this is configured for a prefix since
we've had the IS-IS Anycast prefix flag for some time. [...]
Example from one implementation:
router isis 1
interface Loopback0
prefix-attributes anycast
Ok - than this would support keeping the config in the OSPF YANG model as
Yingzhen has proposed. Authors, let’s keep it there.
Its not a great solution IMO. I think I agree with the direction of your
earlier questions, (e.g., the property can also be advertised in IS-IS).
Anycast prefix is an IGP agnostic concept -- an anycast prefix is a prefix is
associated with multiple nodes in the network.
This also isn't an interface wide property it's a prefix property. Someone earlier said,
"most of the time the user doesn't configure multiple prefixes on their
loopback", I'm not sure that's true, especially if we consider supporting (multiple)
anycast application uses along with non-anycast applications.
Anyway, to have the only configuration option only cover "most of the time"
cases doesn't seem great.
A more precise config is to augment the interface prefix configuration
(ietf-ip) as suggested by Acee earlier (I think).
When ietf-ip was suggested, Yingzhen (I believe), asked how to configure the
protocol to distribute the property then. Why not just distribute it if it has
been set. What is more likely, that the same loopback is configured under IS-IS
and OSPF but you only want to advertise it's anycast property in one of those
IGPs *or* you have anycast and non-anycast prefixes on your loopback? I think
multple prefixes on your loopback is much more likely between those two. And if
you've used multiple loopbacks to support multiple prefixes, well that solution
still works with the ietf-ip augmentation as well.
Thanks,
Chris.
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