BGP on /32 (/128) interfaces

[Ondrej Zajicek]

On Tue, May 14, 2024 at 03:58:06PM +0200, Arzhel Younsi wrote:
> Thank you all for your replies,
> 
> > Thinking about it, it makes sense to have something like direct mode that
> works with unnumbered interfaces (or ones with /32 address).
> 
> We also think that's would be very useful, either transparently to the user
> (depending on next hop resolution, eBGP/iBGP, IP's subnet mask) or through
> the addition of an explicit "direct" keyword.
>
> What would be the process to turn this thread into a feature request ? And
> would the Bird maintainers be interested in implementing it ?

Hi

I already made it a feature request and plan to implement it.

> Perhaps the presence of the ‘direct’ keyword combined with a manual
> ‘interface X’ in a protocol block could signal to bypass the usual
> evaluation and force a neighbor to be considered ‘direct’?

That seems like a reasonable idea, but it has some caveats. Common IP
range is used not only to find the interface but also to select the local
address. If both 'direct' and 'interface' were changed to not wait
for common IP range, then it may start the session immediately after the
interface went up but before the IP address is assigned to it, using
different IP address, therefore changing the current behavior.

One way would be to make specifying local IP mandatory, another one
would be to add option like 'onlink' to state explicitly that the
neighbor is not expected to be on a shared IP range.

-- 
Elen sila lumenn' omentielvo

Ondrej 'Santiago' Zajicek (email: santiago at crfreenet.org)
"To err is human -- to blame it on a computer is even more so."